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Old 01-23-2022, 02:22 PM   #1
Mini-Skoolie
 
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Exclamation 1970 GMC 4106 transit suddenly won't start - Battery fuse issue?

Hi folks,

I've been lurking here for a while and this is my first post. I've got a beautiful "fishbowl" transit bus (converted by Coachman into an RV in the 70's) that's been starting perfectly since I purchased it about 7 months ago. It's just sitting while I renovate the inside, but I try to start it every couple of weeks and let it run for a bit.

Yesterday I went to start it after it sat for about a month and something weird happened. It's been cold and wet out so I figured it would take a bit to get it going. I have a switch on the battery that I turn off when I'm not starting the bus so it doesn't drain while it sits. I turned the batteries on like usual, I put it in "Day" mode like usual and pushed the start button. It started to rev like it normally does but wouldn't quite turn over. I gave it a rest for a min and tried again (this is normal for this old girl to be sluggish after sitting so I wasn't worried). It continued to rev and my partner sprayed some lighter fluid into the intake (per the previous owner's recommendation for sluggish startups). However after revving a bit longer without turning over it just completely stopped. Everything stopped. The headlights won't turn on nor the blinkers. There's usually a buzzer going while the air is inflating when the knob is in Day mode to start it, but there is no buzz when I change the settings from day to night to park. There is no clicking when I try to start. It's like the electrical went out completely.

There are two brand new batteries. I checked their life and they still have juice. One showed about 80% and one about 70%. I checked the battery cables as far back as I could and I don't see any sign of pests chewing through wires. I don't see any sign of electrical burn out/frying as far as I can see but the web of wiring is pretty messy looking both in the driver side panel and the engine so it's hard for me to see which wires are still active after so many years of previous owners' updates.

The only thing I can think might be happening is a blown battery fuse? I haven't yet been able to find the manual for this bus, so I have no idea where the battery fuse would be at this point but I'm hunting.

Does anyone have any ideas on what could be going on and where I should start looking to troubleshoot? Thanks for your time!

Mary

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Old 01-23-2022, 02:44 PM   #2
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Step one -- remove, charge and test the batteries. New batteries lose their charge too.
Step two depends on the results of step one.
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Old 01-23-2022, 02:54 PM   #3
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I tested them and one is about 80% life and one about 70%. I charged the 70% one for a while and tried the headlights again and nothing.
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Old 01-23-2022, 04:18 PM   #4
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You're asking these questions in the wrong forum. These are school bus guys and very few have any knowledge of transit or coach vehicles. True, it appears you have a simple, across the board, electrical supply problem common to any battery supplied vehicle, but the designs, methods and equipment used to control the electrical systems are radically different, and so much more complicated, than most here are familiar with.

First of all there never was a GMC PD4106 "Transit" bus. A GMC Transit or Suburban design model started with either a "S" for Suburban or "T" for Transit. Then it had a "D" since by then they were all Diesel (in all cases at that time era), as well as all being Detroit 2-strokes with the patented GM V-drive configuration. Then it was either an "M" for Manual shift transmission or an "H" for the Hydrashift, 2-speed usually, well 1-speed actually with a long torque converter interval, automatic. The Fishbowl windshield design was a long lasting style and built for many years in very many lengths, engine sizes either 6V-71, or 8V-71, and M or H transmissions. A typical common one would be a TDH-53xx denoting a Transit, Diesel, Automatic, with a 40ft, 53 Pax design capacity (seating arrangements varied a lot though), or a SDM 53xx for a Suburban, Diesel, Manual used for higher speed suburban routes and usually had all forward facing seats.

I've driven 4106's and some of the fishbowls of various types through the years and you'll find it interesting that due to the GMC vehicle design and production philosophy, in a general kind of way the fishbowl and all transit and suburban buses were in fact using the same key engine and driveline components from the PD (Parlor Car) highway Coaches. From the time of the 4104, and the transits built then, to the 4106 era with the 6-8V engines GMC went to great lengths to use common parts and controls where possible. All PD4106's were 8V-71 powered. The city bus models had the option for 6V-71's.

That's why you have that crappy single twist knob to control the engine and lights. I always hated that for it's lack of specific control of the lights and engine as well as it's reliance on relays to enable the function selected. "DAY" start engine with no lights, "NIGHT" to turn on all lights, head and clearance, and "PARK" to shut off engine and headlights but leave clearance lights on. It sucked so bad it stunk on ice. The driver had no control over anything but what that stupid knob provided.

So in effect you can say that in a way you do have a "4106" underneath the skin, and all major driveline and control electrical systems, wearing the trappings of a then current GM transit/suburban fishbowl style body.

I'd deal with making sure the batteries are in the best charge condition you can achieve before trying to start again. Then assuming that you have checked the electrical system and all grounds to be in good condition as well as the battery cutoff switches functioning and providing both batteries to the system, attempt a restart.

BUT, And this is Very Important so don't ignore this or fly right by. Read and absorb and comprehend what I'm imparting.

Before actually trying to start it you should make a check that the intake air emergency shutoff damper hasn't been triggered and closed off the air intake to the blower. This is triggered by a button on the driver panel under the side window and usually has a petal plate the pivots out of the way to protect it from accidentally being pushed. This is near that main engine/light control knob. If it has been pushed and the damper triggered you won't ever get the engine to start. It will crank until the batteries are dead or the starter motor is fried, whichever comes first.

If there isn't enough voltage left to activate the relays I mentioned earlier you could experience the same symptoms and appear to be totally dead. Lots of Delco relays all through the GM buses.

Be sure to check and reset the damper though. It's right on top of the blower where the air horn is mounted and you'll see a round solenoid that pulls on a trigger sear type latch, that's the shaft the damper is mounted to. If the sear pawl isn't set in the sear notch on the shaft then the thing has been tripped and needs resetting. You do this by hand and it should be very obvious what to do. They provide a little pin sticking out of the sear collar itself for use in twisting to reset it. If you need help you can search online as well as buying a Detroit engine manual, available on Ebay and other places. You should already have one anyway, as well as a vehicle manual. Look around for the original vehicle ID plate and it will tell you exactly what model you have as well as the vehicle serial number. Very important to find and retain this info. And Get a Manual for your bus.

By the way, did you mean to say real Lighter Fluid like in a cigarette lighter???? The kind that squirts out in a solid stream?? I may have missed something but I've never heard of using lighter fluid as a starting aid in cold weather. I can't see how this would work or provide any help at all. You should go get and use, very sparingly, from any auto or truck supply place, the proper ether based starting fluid in a pressurized can that sprays a mist of vapor into the engine air intake on the left rear corner of the bus. A short 1-2 second spray as, and just a little before you crank the engine is all you should need. If it needs starting fluid very often, even down to temps of near zeroF, you should be worried more about the condition of the engine. An 8V-71 in half way decent condition will start with a snap and roar almost instantly until it gets really, really cold.

That also assumes you have a good electrical and starter system that's cranking it properly to create enough heat in the cylinders to ignite the fuel. It's all tied together. If it's cranking slow or really sluggish you're likely to always have trouble starting it. That's an electrical, maybe wiring, and starting system problem, and needs to be repaired so it cranks the engine with the authority, and speed, it was designed to provide.

In closing I would strongly suggest that you visit the bus conversion magazine site and ask away there. They know coaches and transits and can provide more info on that class of vehicles since many have either owned or currently own GMC highway and transit coaches through the years.


https://www.busconversionmagazine.co....php?board=1.0
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Old 01-23-2022, 09:27 PM   #5
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I think I may have referred to something that will be understood incorrectly. I was talking about the engine air intake casting that channels the filtered air into the top of the blower itself which sits in the valley between the cylinder banks. I've called it an air horn as a reference to it's function as an air induction casting that resembles a horn shape. My bad, and I hope it didn't cause anyone to think I was talking about the vehicles' air powered safety and warning horn mounted under the driver at the front, operated by the floor mounted air valve. Oops. That wasn't my meaning.
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Old 01-23-2022, 09:40 PM   #6
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Mike (Crown Guy) makes good points. A 4106 isn't a fishbowl. And a 1970 GM isn't a 4106...they were only made from 1960-65. A 4106 will have a Detroit 8V71, unless it was repowered. But since we don't know what engine you have...because there's no 1970 4106 fishbowl...we may need more info from the OP.

I suspect the batteries, especially since you say they're at 80% and 70%. How did you determine that? I suggest you do a load test or have one done at an auto parts store. Here's a video which might help explain that: https://youtu.be/ystmn3ly61Q
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Old 01-23-2022, 10:29 PM   #7
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Quote:
Originally Posted by rossvtaylor View Post
Mike (Crown Guy) makes good points. A 4106 isn't a fishbowl. And a 1970 GM isn't a 4106...they were only made from 1960-65. A 4106 will have a Detroit 8V71, unless it was repowered. But since we don't know what engine you have...because there's no 1970 4106 fishbowl...we may need more info from the OP.

I suspect the batteries, especially since you say they're at 80% and 70%. How did you determine that? I suggest you do a load test or have one done at an auto parts store. Here's a video which might help explain that: https://youtu.be/ystmn3ly61Q

I found another post from this OP asking about getting manuals for the bus. In that one it's mentioned that it's the "Mighty" 6V-71.... or something like that, which nails it as post 4106 and a typical fishbowl era transit which had lots of 6V-71's installed, all around the same time that the 4106 was still in production. Much research and digging into the history of the GM's needed for the OP to clarify her vehicle and what she's dealing with.
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Old 01-24-2022, 06:48 AM   #8
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Quote:
Originally Posted by Crown_Guy View Post
I found another post from this OP asking about getting manuals for the bus. In that one it's mentioned that it's the "Mighty" 6V-71.... or something like that, which nails it as post 4106 and a typical fishbowl era transit which had lots of 6V-71's installed, all around the same time that the 4106 was still in production. Much research and digging into the history of the GM's needed for the OP to clarify her vehicle and what she's dealing with.

were there optional drivetrains? I have a fishbowl (that I need to get off my arse and start restoring).. that is an 8V71 with a 4 speed stick. it also has regular dual sets for forward facing seats more like what was seen in a 4106 ..


as for the OP and his bus, we were bringing a fishbowl back to live last spring and ran into a similar issue.. at one point the electrical system just went dead.. in our case we ended up finding that the Main ground from the batteries was the issue.. it seemed tight, looked good but apparently didnt make enough contact.. ended up pulling it, installing a new terminal, wire wheeling the frame where it attached and using new bolt.. bus fired right up.. the fuel solenoid on those seems to need a really solid voltage.. so I could imagine if the OP was having a voltage issue that the solenoid could be going "open-close..open-close" as the voltage rises and falls trying to start it.
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Old 01-24-2022, 01:20 PM   #9
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Hey, thank you so much for taking the time to write all of this out. I don't know anything about buses and trying to dig up info on this one has been like pulling teeth as I'm unaware of what resources are out there for old rigs like this. So thanks for sharing those links to the other site and the info about the museum. All I have to go on is the small bit of info that the last owner had on it (which isn't much). They said it was a 1971 GMC 4106 motorhome with a 6v-71 Detroit diesel two stroke engine, allison transmission 2 speed w/OD. They said it was never used as a transit bus but was immediately built out into an RV by Coachman that same year. It's 35 feet. I've attached a link to a pic of the exterior below.

RE: Starter fluid - Correct, I meant starter fluid not lighter fluid. I've never used it until this week when the bus was hesitating so I thought it couldn't hurt given what the last owner said. I'm unaware if this is something they did often. My partner says he did just a couple of quick sprays into the intake, but that's when everything shut down. Good point about a strong system not needing this. I'm going to need to get a diesel mechanic out here to look everything over. There were some other questions that came up when driving it but this electrical shutdown is a new issue.

RE: The intake air emergency shutoff damper - I've posted a link with some photos of the driver's side panel and front dash so I can try to understand where you'd be pointing to. This isn't something I'm familiar with. You're saying this should be on the window side under the panel?

https://imgur.com/a/ZU90TR5

Thank you again,
Mary
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Old 01-24-2022, 01:26 PM   #10
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Sorry, still figuring out how to response to each thread.
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Old 01-24-2022, 01:27 PM   #11
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Quote:
Originally Posted by rossvtaylor View Post
Mike (Crown Guy) makes good points. A 4106 isn't a fishbowl. And a 1970 GM isn't a 4106...they were only made from 1960-65. A 4106 will have a Detroit 8V71, unless it was repowered. But since we don't know what engine you have...because there's no 1970 4106 fishbowl...we may need more info from the OP.

I suspect the batteries, especially since you say they're at 80% and 70%. How did you determine that? I suggest you do a load test or have one done at an auto parts store. Here's a video which might help explain that: https://youtu.be/ystmn3ly61Q
Thanks for the comment and the link. I'll give it a watch. I have a trickle charger that's supposed to check voltage. When connected to one battery is registered at 80% power and the other was 60 until I charged it to 70%.
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Old 01-24-2022, 01:29 PM   #12
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Thank you, I've written out a longer response with more information that I think is still being reviewed by the mods.
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Old 01-24-2022, 01:31 PM   #13
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Quote:
Originally Posted by Crown_Guy View Post
I found another post from this OP asking about getting manuals for the bus. In that one it's mentioned that it's the "Mighty" 6V-71.... or something like that, which nails it as post 4106 and a typical fishbowl era transit which had lots of 6V-71's installed, all around the same time that the 4106 was still in production. Much research and digging into the history of the GM's needed for the OP to clarify her vehicle and what she's dealing with.
I am going to need to do more digging to look up the ID number for this thing. All I have is an RVI registration number. I've posted a link to a photo of the the bus in my response to Crown Guy that I think is still being reviewed by mods.
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Old 01-24-2022, 01:34 PM   #14
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Quote:
Originally Posted by cadillackid View Post
were there optional drivetrains? I have a fishbowl (that I need to get off my arse and start restoring).. that is an 8V71 with a 4 speed stick. it also has regular dual sets for forward facing seats more like what was seen in a 4106 ..


as for the OP and his bus, we were bringing a fishbowl back to live last spring and ran into a similar issue.. at one point the electrical system just went dead.. in our case we ended up finding that the Main ground from the batteries was the issue.. it seemed tight, looked good but apparently didnt make enough contact.. ended up pulling it, installing a new terminal, wire wheeling the frame where it attached and using new bolt.. bus fired right up.. the fuel solenoid on those seems to need a really solid voltage.. so I could imagine if the OP was having a voltage issue that the solenoid could be going "open-close..open-close" as the voltage rises and falls trying to start it.
Interesting, thank you for sharing your experience. I'll check those terminals again and try to tighten the connectors and see if that makes a difference. They looked good to me too, but maybe not.
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Old 01-24-2022, 07:34 PM   #15
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Quote:
Originally Posted by cadillackid View Post
were there optional drivetrains? I have a fishbowl (that I need to get off my arse and start restoring).. that is an 8V71 with a 4 speed stick. it also has regular dual sets for forward facing seats more like what was seen in a 4106 ..


as for the OP and his bus, we were bringing a fishbowl back to live last spring and ran into a similar issue.. at one point the electrical system just went dead.. in our case we ended up finding that the Main ground from the batteries was the issue.. it seemed tight, looked good but apparently didnt make enough contact.. ended up pulling it, installing a new terminal, wire wheeling the frame where it attached and using new bolt.. bus fired right up.. the fuel solenoid on those seems to need a really solid voltage.. so I could imagine if the OP was having a voltage issue that the solenoid could be going "open-close..open-close" as the voltage rises and falls trying to start it.

There weren't all that many different options for the drive-line and transmission. There were only 6V-71 and 8V-71 engines available at the time and the V-drive was a fixed and immutable GM innovation. The transmissions were going to be either the 4-speed Spicer manual or the 1-speed slush box with the massive torque converter, since it actually stayed in torque converter until about 30mph when it finally locked up. Truly only designed for heavy, stop and go, low speed city traffic.

They may have had at that time a real 2-spd version, and they did also in later years build the V-730 which is supposed to have 3-speeds which have successfully been put into many (PD)4106, 4107, 4108, 4903, 4905 highway Coaches. I freely admit to not being well versed on the many flavors and species of the suburban and transit automatic transmission varieties. Just haven't had the exposure to them.

I can say with authority that that Fishbowl you described as owning is a keeper, since it was built for longer Suburban routes at freeway speeds. That engine transmission combination, as well as the forward facing seats, like a Coach, obviously makes it a Suburban configuration, which means that under the skin and where it counts in the drive-line, 8V power, manual 4spd, and rear end final drive ratio, it's for all intents and purposes a Parlor Car highway Coach drive-line underneath that Transit Fishbowl exterior body-style. Mostly exactly like a 4106 or 4107, depending on the year it was built. A veritable wolf in sheep's clothing.

It will have many trappings and parts common to the transit buses, but it will also have the essential drive components and probably have some of the exact same parts as used in the 4106, 4107 at that time. The year of the thing will determine which it is. I'm going to guess that it has an ID plate with a model something like SMD45(53)03 or something like that. The overall length will determine the Pax count on the ID, 45 or 53. The real trick is to get one that's been taken care of with good maintenance, and not all corroded by road salts. Western buses again if possible. I've seen a few through the years that looked real good.

I've driven a few of these through the years and they are not bad at all. For a conversion vehicle they have many good features. Rear engine, and if it has the optional through luggage compartment(s) that's a biggy too. They have a lower floor than the highway coaches and the luggage compt., if it even has one, and there were usually only just one, won't be as tall and accommodating as the Coaches. These suburbans were built for metro routes of less than 70 miles or so and not for multi-day cross country passenger service, so they had no need for massive luggage bays. They will scoot down the road like a Coach and should do an honest 70+, the ones I drove handled pretty well.

They also came with engine driven factory A/C like the coaches, even though they had the Condenser located up high above the rear body in a separate fairing. Like I said, they were mostly the same except where they were different due to constraints of the body style and where they could locate the various equipment.

SMD Suburbans are an actual good compromise between a strictly school bus vehicle and a full blown Highway Coach. They will have many of the same systems as a highway coach, air-ride suspension, A/C (usually), 4spd manual transmission, complex electrical and control systems, which will up the potential for failures and repairs, but overall they are potentially a good bet.

They will not be cheaper to keep, and will have most of the same failures as a highway coach, but you might be able to buy one initially much cheaper. Most folks don't see them as a viable option.

But you must know that the Suburbans, having 8V's usually, with the 4spd transmission is the way to go, NOT the Much more common, Transit TDH versions, mostly having only a 6V-71 with the automatic transmission and road speed of about 55-60 if you're lucky. They won't hang together for hours and hours of sustained highway speeds. Weren't designed for it and will get hot and fail. Plus the 6V in a 40ft bus is way under-powered and will cause all kinds of trouble if you ever want to leave the blacktop, or pull a more than moderate hill, God help you if you ever get stopped on the hill. Go ahead, ask me how I know......

At least with the slush box Auto trans you may be able to get up a hill, eventually, but if you have a 6V in a forty foot bus with a manual 4spd you really are playing with fire, go ahead, ask me how I know this too...
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Old 01-24-2022, 09:39 PM   #16
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Quote:
Originally Posted by hopinpuddles View Post
Hey, thank you so much for taking the time to write all of this out. I don't know anything about buses and trying to dig up info on this one has been like pulling teeth as I'm unaware of what resources are out there for old rigs like this. So thanks for sharing those links to the other site and the info about the museum. All I have to go on is the small bit of info that the last owner had on it (which isn't much). They said it was a 1971 GMC 4106 motorhome with a 6v-71 Detroit diesel two stroke engine, allison transmission 2 speed w/OD. They said it was never used as a transit bus but was immediately built out into an RV by Coachman that same year. It's 35 feet. I've attached a link to a pic of the exterior below.

RE: Starter fluid - Correct, I meant starter fluid not lighter fluid. I've never used it until this week when the bus was hesitating so I thought it couldn't hurt given what the last owner said. I'm unaware if this is something they did often. My partner says he did just a couple of quick sprays into the intake, but that's when everything shut down. Good point about a strong system not needing this. I'm going to need to get a diesel mechanic out here to look everything over. There were some other questions that came up when driving it but this electrical shutdown is a new issue.

RE: The intake air emergency shutoff damper - I've posted a link with some photos of the driver's side panel and front dash so I can try to understand where you'd be pointing to. This isn't something I'm familiar with. You're saying this should be on the window side under the panel?

https://imgur.com/a/ZU90TR5

Thank you again,
Mary
That's a cutey alright. It's definitely a transit style body since they all had two entry doors. A Suburban would only have the front entry door. 35ft with a 6V-71 makes it not under-powered and should do OK. The limiting factor for 65+ road speed will be the rear-end final drive ratio along with the 1-spd slush box "auto" transmission. That little toggle switch on the dash is all you get for the transmission, either "F" or "R".

Thanks for the pics. Good shot of the panel under the side window. The Red Covered "Emerg. Stop" toggle is the one that will trigger the emergency air cutoff on the intake of the engine. You must lift the Red cover and then actuate the spring loaded toggle switch. This energizes the solenoid coil pulling on the rod attached to the sear latch. The damper plate will drop covering the air intake to the blower. This will strangle and prevent it from getting enough air to run away. It's protected from accidental activation purposely by the red cover.

I've attached some pics of a similar engine (8V-71) from a highway coach and you can see the actual emergency shutdown solenoid and the trigger sear latch that it pulls to allow the spring loaded damper to close. It's the round thing that's bolted right on the side of the large casting that has GM cast in it. That's the air intake that covers the blower intake. The damper plate is inside and pivots on that rod that the trigger sear is mounted to. I hope you can figure that out. It's really very simple and reliable. That's what I was trying to describe before, The engine mechanism itself. Once the toggle switch is actuated just once it releases the sear latch and the damper will drop. That will prevent the engine from starting so it should be checked if there are any cranking with no start symptoms.

I also attached a shot of a typical V-730 3-spd custom modification into this PD4905 highway coach converted to an RV. The rear engine compartment and layout is very similar on all GM coaches whether it's a Transit/Suburban or a Highway Coach. The Sideways mounted left-hand turning V-drive all mounted behind the rear axle was the unique GM innovation and served the whole industry extremely well for many decades. They literally owned the bus market in the city and on the road.

All that carpet stuff covering the dash must be someone's idea of a luxury touch. But I think it looks tacky. You didn't show it too well, but there's a hint of it covering the whole front, I can guess that they continued the process and covered the whole metal area under the front window too. If you're real lucky they didn't bother to remove the ID plate but merely covered it with their faux upgrade. Check it out and if it's still there you're in good shape. It will no doubt be a TDH45xx something like that, since that is exactly what that is. A Transit, Diesel, Hydro-shift, 45 Pax, xx is number of model revision level.

Good to hear you used Starting Fluid. Language details can be important. By the way. In that pic of the engine air intake casting, and the mounted solenoid, you may notice a little round cup thing screwed into the housing with a spring load cap to protect and keep it clean, just to the right of the solenoid. That's a starting aid device designed to have premeasured ether filled capsules inserted into that cup after lifting the cap. There's a hollow piercing pin in the bottom of the cup that lets the escaping ether be sucked into the air intake as the engine is cranked for starting. I'd rather use a can of starting fluid and that's all I've ever used if it was needed. Surprisingly they will start in very cold conditions down below freezing as long as the engine is in pretty good condition and the starter can crank it with authority.
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Old 01-25-2022, 01:19 AM   #17
Mini-Skoolie
 
Join Date: Jan 2022
Location: PNW
Posts: 10
Year: 1971
Coachwork: GMC 4106 by Coachman
Engine: 6V-71 Detroit Diesel Two Stroke
Quote:
Originally Posted by Crown_Guy View Post
That's a cutey alright. It's definitely a transit style body since they all had two entry doors. A Suburban would only have the front entry door. 35ft with a 6V-71 makes it not under-powered and should do OK. The limiting factor for 65+ road speed will be the rear-end final drive ratio along with the 1-spd slush box "auto" transmission. That little toggle switch on the dash is all you get for the transmission, either "F" or "R".

Thanks for the pics. Good shot of the panel under the side window. The Red Covered "Emerg. Stop" toggle is the one that will trigger the emergency air cutoff on the intake of the engine. You must lift the Red cover and then actuate the spring loaded toggle switch. This energizes the solenoid coil pulling on the rod attached to the sear latch. The damper plate will drop covering the air intake to the blower. This will strangle and prevent it from getting enough air to run away. It's protected from accidental activation purposely by the red cover.

I've attached some pics of a similar engine (8V-71) from a highway coach and you can see the actual emergency shutdown solenoid and the trigger sear latch that it pulls to allow the spring loaded damper to close. It's the round thing that's bolted right on the side of the large casting that has GM cast in it. That's the air intake that covers the blower intake. The damper plate is inside and pivots on that rod that the trigger sear is mounted to. I hope you can figure that out. It's really very simple and reliable. That's what I was trying to describe before, The engine mechanism itself. Once the toggle switch is actuated just once it releases the sear latch and the damper will drop. That will prevent the engine from starting so it should be checked if there are any cranking with no start symptoms.

I also attached a shot of a typical V-730 3-spd custom modification into this PD4905 highway coach converted to an RV. The rear engine compartment and layout is very similar on all GM coaches whether it's a Transit/Suburban or a Highway Coach. The Sideways mounted left-hand turning V-drive all mounted behind the rear axle was the unique GM innovation and served the whole industry extremely well for many decades. They literally owned the bus market in the city and on the road.

All that carpet stuff covering the dash must be someone's idea of a luxury touch. But I think it looks tacky. You didn't show it too well, but there's a hint of it covering the whole front, I can guess that they continued the process and covered the whole metal area under the front window too. If you're real lucky they didn't bother to remove the ID plate but merely covered it with their faux upgrade. Check it out and if it's still there you're in good shape. It will no doubt be a TDH45xx something like that, since that is exactly what that is. A Transit, Diesel, Hydro-shift, 45 Pax, xx is number of model revision level.

Good to hear you used Starting Fluid. Language details can be important. By the way. In that pic of the engine air intake casting, and the mounted solenoid, you may notice a little round cup thing screwed into the housing with a spring load cap to protect and keep it clean, just to the right of the solenoid. That's a starting aid device designed to have premeasured ether filled capsules inserted into that cup after lifting the cap. There's a hollow piercing pin in the bottom of the cup that lets the escaping ether be sucked into the air intake as the engine is cranked for starting. I'd rather use a can of starting fluid and that's all I've ever used if it was needed. Surprisingly they will start in very cold conditions down below freezing as long as the engine is in pretty good condition and the starter can crank it with authority.
Great info, thank you much. I'm learning a lot here. I'll be doing some investigating this week to see if I can narrow this down.

You're right, the "rat fur" is everywhere and I'm not a fan. The front dash was fur and wainscoting type panels. I pulled it off and don't recall an ID tag but will look again. The old front side door is gone but the stairs are still there under the floor (turned storage compartment accessible from the outside). I'll look under there too. Fingers crossed I find it!
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Old 01-25-2022, 07:46 AM   #18
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 16,557
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Quote:
Originally Posted by Crown_Guy View Post
There weren't all that many different options for the drive-line and transmission. There were only 6V-71 and 8V-71 engines available at the time and the V-drive was a fixed and immutable GM innovation. The transmissions were going to be either the 4-speed Spicer manual or the 1-speed slush box with the massive torque converter, since it actually stayed in torque converter until about 30mph when it finally locked up. Truly only designed for heavy, stop and go, low speed city traffic.

They may have had at that time a real 2-spd version, and they did also in later years build the V-730 which is supposed to have 3-speeds which have successfully been put into many (PD)4106, 4107, 4108, 4903, 4905 highway Coaches. I freely admit to not being well versed on the many flavors and species of the suburban and transit automatic transmission varieties. Just haven't had the exposure to them.

I can say with authority that that Fishbowl you described as owning is a keeper, since it was built for longer Suburban routes at freeway speeds. That engine transmission combination, as well as the forward facing seats, like a Coach, obviously makes it a Suburban configuration, which means that under the skin and where it counts in the drive-line, 8V power, manual 4spd, and rear end final drive ratio, it's for all intents and purposes a Parlor Car highway Coach drive-line underneath that Transit Fishbowl exterior body-style. Mostly exactly like a 4106 or 4107, depending on the year it was built. A veritable wolf in sheep's clothing.

It will have many trappings and parts common to the transit buses, but it will also have the essential drive components and probably have some of the exact same parts as used in the 4106, 4107 at that time. The year of the thing will determine which it is. I'm going to guess that it has an ID plate with a model something like SMD45(53)03 or something like that. The overall length will determine the Pax count on the ID, 45 or 53. The real trick is to get one that's been taken care of with good maintenance, and not all corroded by road salts. Western buses again if possible. I've seen a few through the years that looked real good.

I've driven a few of these through the years and they are not bad at all. For a conversion vehicle they have many good features. Rear engine, and if it has the optional through luggage compartment(s) that's a biggy too. They have a lower floor than the highway coaches and the luggage compt., if it even has one, and there were usually only just one, won't be as tall and accommodating as the Coaches. These suburbans were built for metro routes of less than 70 miles or so and not for multi-day cross country passenger service, so they had no need for massive luggage bays. They will scoot down the road like a Coach and should do an honest 70+, the ones I drove handled pretty well.

They also came with engine driven factory A/C like the coaches, even though they had the Condenser located up high above the rear body in a separate fairing. Like I said, they were mostly the same except where they were different due to constraints of the body style and where they could locate the various equipment.

SMD Suburbans are an actual good compromise between a strictly school bus vehicle and a full blown Highway Coach. They will have many of the same systems as a highway coach, air-ride suspension, A/C (usually), 4spd manual transmission, complex electrical and control systems, which will up the potential for failures and repairs, but overall they are potentially a good bet.

They will not be cheaper to keep, and will have most of the same failures as a highway coach, but you might be able to buy one initially much cheaper. Most folks don't see them as a viable option.

But you must know that the Suburbans, having 8V's usually, with the 4spd transmission is the way to go, NOT the Much more common, Transit TDH versions, mostly having only a 6V-71 with the automatic transmission and road speed of about 55-60 if you're lucky. They won't hang together for hours and hours of sustained highway speeds. Weren't designed for it and will get hot and fail. Plus the 6V in a 40ft bus is way under-powered and will cause all kinds of trouble if you ever want to leave the blacktop, or pull a more than moderate hill, God help you if you ever get stopped on the hill. Go ahead, ask me how I know......

At least with the slush box Auto trans you may be able to get up a hill, eventually, but if you have a 6V in a forty foot bus with a manual 4spd you really are playing with fire, go ahead, ask me how I know this too...

Love when you post about the old stuff.. i always learn!! my fishbowl still has its seats (I am keeping it seated).. does have A/C (looks to be all there).. its not a southwestern bus but corrosion isnt bad overall and the plywood is still solid.. the biggest challenge im facing right now is finding front glass for it.. all 6 panels and the rubber are damaged.. the custom glass shop I once used for classic vehicles is no longer around (the guy retired and sold off the assets).. so finding a complete set (and someone to put them in) is a big endeavor...
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Old 01-26-2022, 05:08 PM   #19
Bus Nut
 
Crown_Guy's Avatar
 
Join Date: Dec 2013
Location: SoCal
Posts: 320
Year: 1989
Coachwork: Crown Coach
Chassis: 40ft 3-axle 10spd O/D, Factory A/C
Engine: 300hp Cummins 855
Rated Cap: 91
Quote:
Originally Posted by cadillackid View Post
Love when you post about the old stuff.. i always learn!! my fishbowl still has its seats (I am keeping it seated).. does have A/C (looks to be all there).. its not a southwestern bus but corrosion isnt bad overall and the plywood is still solid.. the biggest challenge im facing right now is finding front glass for it.. all 6 panels and the rubber are damaged.. the custom glass shop I once used for classic vehicles is no longer around (the guy retired and sold off the assets).. so finding a complete set (and someone to put them in) is a big endeavor...

Yepper. Windshields are the curse of our hobby for sure. You're not alone in that. I live in terror of having to find replacements for the two curved windshields on my Tandem (the avatar). Until I get a pair of replacements in hand against the day of need I will always be worried about gravel trucks, (never follow), and random damaging missiles heading my way. Which is one of the many reasons I got my second Crown 35ft, with 2-axles, 6-71T, 10spd RoadRanger, and the much more common and standard Crown FLAT glass arrangement. I consider it my nimble, off highway, into rough unknown conditions, camp Crown. Flat glass is a no-brainer to repair/replace anywhere at all.

GMC coaches of all flavors are in the same boat, as the usual sources today are to find a serviceable set in a salvage yard, a hangar queen somewhere. Good Luck. I hear there are some places around that claim to have New Old Stock who could be very nice to know about, but I'm sure the prices would be very uncomfortable. It's all part of the price we pay for indulging ourselves in an historic vintage vehicle, never mind they were never as numerous as any cars would have been so the available numbers are much lower. Join me in the Happy, Hunting (always) Brigade.
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Old 01-27-2022, 06:51 AM   #20
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 16,557
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Quote:
Originally Posted by Crown_Guy View Post
Yepper. Windshields are the curse of our hobby for sure. You're not alone in that. I live in terror of having to find replacements for the two curved windshields on my Tandem (the avatar). Until I get a pair of replacements in hand against the day of need I will always be worried about gravel trucks, (never follow), and random damaging missiles heading my way. Which is one of the many reasons I got my second Crown 35ft, with 2-axles, 6-71T, 10spd RoadRanger, and the much more common and standard Crown FLAT glass arrangement. I consider it my nimble, off highway, into rough unknown conditions, camp Crown. Flat glass is a no-brainer to repair/replace anywhere at all.

GMC coaches of all flavors are in the same boat, as the usual sources today are to find a serviceable set in a salvage yard, a hangar queen somewhere. Good Luck. I hear there are some places around that claim to have New Old Stock who could be very nice to know about, but I'm sure the prices would be very uncomfortable. It's all part of the price we pay for indulging ourselves in an historic vintage vehicle, never mind they were never as numerous as any cars would have been so the available numbers are much lower. Join me in the Happy, Hunting (always) Brigade.

ha!! you know it glas is always a thing.. with busses theres zero aftermarket support.. need a curved glass for a 57 chevy? theres plenty since its a popular vehicle to restore.



I suppose if there were engineering drawings around with exact sizing someone would have a better chance at making these windshields..



whats even sadder is that when we resuced a bunch of busses from a failed museum attempt in ohio during late 2019 is that there about 6 sets of formerly good fishbowl windshields that bad been apparently neatly stacked inside one of the busses.. however at one point that bus had been towed someplace and the glass wasnt secured so all of it was destroyed..



hey while you are here.. what do you recommend for a starter on a detroit? I hear some people say a chevy gear reduction starter fits.. some say stick with factory or have OEM unit rebuilt.. what are your thoughts?
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