1968 GM Coach Bus Questions.

[blessed-adventurers]

Hi all,

Finally found a bus that we like. I am looking at a 1968 GM Coach Bus with a 8-71 And 4 speed manual trans. It has already been converted. We will be making some modifications to the current build to fit our lifestyle.

Is there anything negative, pros-cons, I need to know about this specific bus year and style before buying?

Are they reliable?

Any major concerns?

Thanks!

[ol trunt]

I love the DD8-71's but be sure you know of a qualified mechanic to take care of it. Both parts and mechanics are becoming scarce and repairs are VERY expensive. The 2 stroke diesels are rapidly heading towards extinction.
Jack

[cowlitzcoach]

If it is a 35' single deck bus it is a 4106. If it is more than a single deck or 40' it is a Buffalo.


Both are very good buses but they do have their weak spots. The biggest problems with all of them, regardless of the model, is over the years engines with more HP have been installed in them. The bulkhead that supports the engine cradle at the back of the bus is prone to failure after a bazillion miles anyway. Increase the HP and torque of the engine and the bulkhead will tend to start to crack sooner. It will exacerbated if someone has put a trailer hitch on the back and hasn't reinforced the attachment points for the trailer hitch. When the bulkhead fails catastrophically it will leave the engine, transmission, and rear end behind as the bus continues on until the dragging on the pavement stops the bus.


The 2-cycle Detroit Diesel is one of the easiest engines to keep and maintain. They are very particular about oil (only Delo 100 40 wt or the equivalent) and very particular about overheating. If you don't know someone who really knows a 2-cycle DD you are going to need to school yourself on the care and feeding of one yourself. You will know if they really know or whether they just say they know all about 2-cycle DD's if they talk about copper washers.


If the price is low enough and you like the bus I would take a flyer on one. But it is what it is. Because it uses a V-drive with the engine mounted transversely there are very few different rear end gear sets available. Most can give reasonable highway speeds but if it is a highway racer it will be a dog on the hills. Updating to an automatic has problems as well. The only buses that came from the factory with an automatic V-drive were the transit buses. Some of those transmissions were only 2-speed which was great around town but really limits you out on the highway.


Good luck!

[cadillackid]

I LOVE the 4106s and Buffalos.. friend of mine has a completely original Buffalo with Air-Conditioning he recently acquired.. Love the sound of those big DD's...



the multi-level effect of those busses makes them really cool to do neat things with your conversion.

-Christopher

[blessed-adventurers]

The one I'm looking at is a 35' single deck 4106 or the 40' I'm not exactly sure. Thanks for the reply so far all! What is the top speed on the interstate for the 4 speed manual and DD8V-71? And how many MPG does it get?

[cowlitzcoach]

Most of the 4106's had no problem cruising at 70 MPH.


Fuel mileage is going to be in the 6-9 MPG range.

[84chevyguyid]

I have a 76 GMC coach that my dad converted 18 years ago, has an 8-71 with a v drive trans. Not sure if you call it a 3 speed or a 2 speed. Has fluid drive from a stop till about 20 mph at which point it locks into direct drive then at about 40 it shifts into overdrive. Will do 73 mph max. I hauled the car in the pic on a 250 mile trip to the drag strip pushing a 30+ mile an hour headwind and when I go there and checked the mileage, it got 5 mpg. Drove it home the next weekend with no wind and no trailer/car and checked it again, 5.2 mpg. Its about 41 foot bumper to bumper and weighs around 24,000 full of water and fuel. The nice part about the coach is it has a tall ceiling and is 102" wide, feels way roomier than a skoolie.

[cowlitzcoach]

Originally Posted by 84chevyguyid

I have a 76 GMC coach that my dad converted 18 years ago, has an 8-71 with a v drive trans. Not sure if you call it a 3 speed or a 2 speed. Has fluid drive from a stop till about 20 mph at which point it locks into direct drive then at about 40 it shifts into overdrive. Will do 73 mph max. I hauled the car in the pic on a 250 mile trip to the drag strip pushing a 30+ mile an hour headwind and when I go there and checked the mileage, it got 5 mpg. Drove it home the next weekend with no wind and no trailer/car and checked it again, 5.2 mpg. Its about 41 foot bumper to bumper and weighs around 24,000 full of water and fuel. The nice part about the coach is it has a tall ceiling and is 102" wide, feels way roomier than a skoolie.

This bus is a Suburban version of the GM transit bus.

[Iceni John]

I suggest you make friends with the good folk on the Bus Conversion Magazine (BCM) forum. A bus like what your looking at is what tickles their fancy almost more than anything else, and plenty of folk there have GMs of various vintages and ancestry. Between all of those old farts there's not much they don't know about them, especially Clifford Allen AKA Luvrbus who is the definitive source of real-world knowledge and wisdom - whatever he says is always, and I mean always, 100% correct. Ignore his advice at your peril! I've been a member of the BCM forum for as long as I've owned my bus, even though they probably think a Crown is a mere pretender compared with their "real" buses. Mind you, my bus has exactly the same drivetrain as a MC9 Greyhound bus of the same age, so that's my excuse!

If you do buy it, my friend John Usle AKA Siberyd is compiling a register of every 4104 and a lot of other GMs, and he or one of the other cognoscenti will be able to look up the entire life history of the bus's ownership. How cool is that?

John

[Crown_Guy]

Be VERY careful about exactly which model you have. Simply calling something a "GM Coach" will not end well if it's the wrong kind of bus. GM built, Highway Inter-City, Suburban's for outlying areas, and inner-city Transits. They all were built for different operational requirements. GM Highway Coaches were all "P"arlor car "D"iesel followed by a model number 4104, 4106, 4107, 4108, all two axle 35ft by the way, the PD4501 (Scenicruiser is 40ft with three axles, only one of which is driving), and not many other's except at the end they changed the numbering convention, but these were mostly after the 4107 era and were late model so called "buffalo"s, which are NOT double deck, even though they look it, it's an optical illusion to create taller luggage bays.

You should look for the builder ID plate on the front vertical dash area just inside the entry door. A lot of conversion dudes like to remove or cover it up so if it's not easily found you can look in the openable (from the outside) compartment right under the driver seat floor. If there IS a compartment it is a Highway coach, and the model # and serial number will be deeply stamped in the frame at the rear of the compartment behind the clutch linkage, steering shaft, and brake valve and throttle linkage. That's looking straight into toward the bus center line, on the fore and aft bulkhead, not the one to your right toward the rear of the bus going port to starboard. The model numbers will be a combination of beginning Letters, followed by model Numbers, then another field of numbers which is the serial number of that bus. Example PD4106 1234. Parlor car Diesel, 41 (passengers), model 06(body style).

If there isn't any enclosed compartment there, then it's NOT a highway coach. It's some flavor of Suburban or Transit bus. The body style will be different from any highway coach and most likely, for a 1968 vintage, have the "fishbowl" style windshield(s). It also won't have the full sized, between the axles, underfloor luggage compartments, only the highway coaches have those.

Bottom line is find out, and be Very sure of what you're dealing with, and how long it is, 35ft, 40ft. Without the exact builder plate data on model and even serial number you're just wasting your time and will end up with something other than what you expected to get. Road speed, MPG, parts availability, even corrosion and total vehicle miles, and the type service it was in, will inform your decision to pull the trigger or not.

I learned on Crowns, and GM coaches, and have driven uncounted hundreds of thousands of miles on all types of GM's, and I love them to death. They were truly the best Fleet owners bus, excellently designed and engineered, and built like battleships. Simple, reliable, and relatively inexpensive to keep and repair. For the drivers they are sublimely superior to drive and handle on the road, the best Coaches by far and none today can compare. Look at a well cared for example today of a 60 year old 4104 for instance and you'll find it doesn't show it's age and wears it well. You can't say that at all for the newer flashy coaches like Prevost, VanHool, Setra, and even the MCI's don't age as well as a good GMC, but they're the close second best for long lived service. Today the GMC is a lot harder to find parts, and takes a dedicated owner willing to really get involved and learn the coach inside and out.

Another thing to consider is the simple chore of shifting the gears on a GMC. It can be a truly harrowing experience for the un-initiad with no instructor to help. The bear trap, over-center style clutch, possible air assist if it's a 4106, and it's working properly, the insanely fast shifting speed when cold, until the engine and transmission warms up, any sloppiness in the shift linkage is to be considered and compensated for. It could indicate either corrosion and or plain old lack of service, lubrication, and wear and tear which should be fixed, if possible.

All kinds of things to consider. Which you should very soberly, your bank account will thank you. ALL highway/suburban/transit style coaches will inherently cost more to get everything done on them compared to a school bus. Air Conditioning systems, air-ride suspension, complicated electrical, maybe 24 volt to boot. A whole different breed of cat, not better or worse, just different, with a whole new level of equipment and maintenance requirements along with oodles of unique GM coach proprietary parts and such.

Depending on your needs and desires and where you intend to take it, a Coach may work, or it may not. Remember a Coach is a HIGHWAY designed bus, mostly paved, flat or highway engineered grades, with Highway gearing and terrible, and I mean dangerous, limitations on where you can take them and how steep grades will defeat your ability to get in and out. Just a single steep driveway can kill you and get you stuck/stalled with maybe no way out, and if you're lucky you MAY be able to back out. One problem with that is that the reverse gears are all just a little bit higher than the 1st gear, so if you can't pull it in 1st, reverse won't be any better. Then there's the fun reverse solenoid thing.....but that's another whole story, and a new set of defensive tactics to protect yourself from that thing failing.

I'd listen to John too and look into the various forums specializing in Coaches of all types for conversions. There is a lot of experience and answers to be found in them.

These should be considered real serious, professional, long lived, and very high mileage coaches with engineering and maintenance requirements to match. For the right owner they can be blissful to own and drive, but for the un-informed and un-prepared, they will break you without a second thought since they were designed for experienced Fleet operators in high mileage (100k+ year), daily passenger service.