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Old 03-02-2021, 12:10 AM   #1
Mini-Skoolie
 
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Dangerously slow bus... help needed!

Hey all, I was out driving my bus on the interstate the other day after getting the oil changed. The bus had always been a bit slow but I’m starting to think all the extra weight from interior renovations have taken their toll.

I just couldn’t help but feel like it was a bit dangerous to be driving a bus that can only go 65 tops on the interstate, and even slower up hills. It feels especially hazardous when merging with cars going 75-85+.

And when going up a steep grade (I live on a mountain), the bus only goes about 30 mph tops. It’s a bit unnerving to be constantly flooring it, not getting enough speed, and hearing the transmission basically screaming.

I know I’m not the first to have this issue and I understand it’s normal for every bus to be a little slow, but for safety’s sake I’m looking for ways to get about 10 more mph out of this thing, and maybe a little more power going up hills.

My bus is a 1988 GMC Bluebird, with the 8 CYL 8.2L Detroit Diesel “fuel pincher” engine. Mine is naturally aspirated (not turbocharged) and gets about 165 horsepower at 3,000 RPM.

I’ve been trying to find info on the transmission all day with no luck. I’ve been told it’s an Allison transmission, but at this point I don’t know what the gear ratios are.

Obviously this is not a bus created with speed/power in mind, but since I’m having safety concerns, I want to see what my options are in terms of engine/transmission/differential upgrades.

So my question is this:

If I had a budget of around $2,000-3,000, what improvement(s) would be the best use of my money to give this thing more power?

Feeling a little bummed since I put 2+ years of hard work and TLC into this bus and I don’t feel safe driving it with its current capabilities.
So any and all input/thoughts/ideas are very well appreciated.

Thanks!
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Old 03-02-2021, 12:20 AM   #2
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The 8.2 is actually a marine / industrial engine and was not really meant for highway vehicles, though GM was known for trying to make square pegs fit round holes back then. They are known for head gasket issues with excessive heat and stress (a given with hilly terrain), and that heat and stress can also fry the transmission if you're not careful. That being said, there is is hope in a repower within your budget if you're handy with tools and don't mind doing some, most or all of the work yourself.

Motorhomes that have been ruined by leaky roofs can be had any old time for cheap or free if you're sharp, and they have more powerful, perfectly good low-mileage mechanicals that are ideal for upgrading a platform such as yours. A late-model P30 or WorkHorse chassis motorhome could be pillaged for its 7.4L Mark IV / 8.1L LS big-block. IF you can get your hands on a 502 GM V8, that is also a valid option, though I doubt your budget will land one.

The Mark IV is a bit more powerful than the 8.2, and the LS is equally so, with slightly better fuel economy, and depending on the weight involved, you might even further benefit from the right automatic transmission if not already equipped (the TH400/TH475 or 4L80/4L85E, NOT the 700R4 or 4L60E unless your bus is a smaller one).

The Mark IV will more readily bolt to your existing transmission, however, and I don't think it will be too much power for an AT545 if that's what you have. It can be identified by a tag on the right side of the rear housing, it will clearly say AT545, or MT643. If it is an AT545, that is part of your problem as well, it is not a bad transmission, but not well-suited for hilly terrain or highway driving, especially with the 8.2. Perhaps a suitable donor big-block motorhome would have a trans better suited to the purpose, but either way, you may want to invest in larger trans cooler(s),

Matter of fact, if you're near Virginia and don't mind the ride to get it, my old man happens to have an '83 Fleetwood Pace Arrow with 65k original miles on the carb'd 454 / TH400 setup, ripe for the plucking, complete with fuel tank, and it runs and drives. Someone was supposed to have bought it for exactly that purpose but never showed up. I think he was asking $1500 for the whole thing, but I would have it towed for stripping. Reason being the roof leaked badly. Mold has taken over the rear third of the interior and it has quite a bit of (what is now) junk stored in it. I'm not sure I would want to drive it without some kind of respirator mask. It hasn't been driven in a long time either.

One other possible swap candidate if you're feeling froggy and can locate one, would be a 472 / 500 Cadillac big-block, 425/455 Oldsmobile, 455 Pontiac, or 430 / 455 Buick. Loads of torque, which is what you need, and not too difficult to adapt to your existing trans, methinks.
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Old 03-02-2021, 12:42 AM   #3
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Simply stated, the 8.2 is woefully underpowered for highway use. As you've stated, it'll barely get out of its own way. Your transmission is 99.9% likely to be the AT545.
Good luck, there's not much of an easy/cheap way to give these a big horsepower boost.
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Old 03-02-2021, 03:25 AM   #4
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The cheapest route would be a big block chevy I agree. That 8.2 is a disaster combine that with an at545 even worse. A 454 should bolt up to the at545 If you buy performance parts off craigslist you can get them way cheap. If you go that route I am happy to give you a build sheet that should make a suitable engine. I have done several high performance truck engines on the big block chevy platform and can make a ton of power on Almost any budget.
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Old 03-02-2021, 07:27 AM   #5
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I'll echo what the others have said. In that your 8.2 simply won't cut the mustard. Improvements can be made to them, but they have headgasket and reliability issues in stock form, so boosting the power will only make those problems worse. And if you have an at545 behind it, nothing you have will work for your desired goal.

I'm apparently going against the grain though, and will not recommend a gas engine swap. I recommend you look for and purchase a donor of some sort. You can find cheap box trucks, school buses, and even semi trucks that are rusted out with more desirable drivetrains that will be suitable for your needs. For instance, there is an f6000 with an cummins C/mt643 near me for 2500 bucks that is screaming my name.

But, the big roadblock here might be the fact that to do any swap, you'll need some fabrication and problem solving skills. Even to swap a 454 in the bus will require different/custom motor mounts. Do you have the equipment and skills to do such a thing? If not, live life in the slow lane like most on here.

One thing you didn't mention and probably hadn't thought of, is braking. You'll need more of it if you're planning on having a 70 mph cruiser or if you're driving in the mountains at faster speeds. And schools that tended to select the cheaper engine/trans (8.2/at545) options on the build sheet, also tended to select the lighter and cheaper axle options as well.

Don't skimp on your brakes. As dangerous as merging with faster traffic can seem, flying down the side of the mountain with failed brakes is a lot worse. One is a fender bender, the other is your life.
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Old 03-02-2021, 08:11 AM   #6
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Quote:
Originally Posted by silvermachine View Post
Hey all, I was out driving my bus on the interstate the other day after getting the oil changed. The bus had always been a bit slow but Iím starting to think all the extra weight from interior renovations have taken their toll.

I just couldnít help but feel like it was a bit dangerous to be driving a bus that can only go 65 tops on the interstate, and even slower up hills. It feels especially hazardous when merging with cars going 75-85+.

And when going up a steep grade (I live on a mountain), the bus only goes about 30 mph tops. Itís a bit unnerving to be constantly flooring it, not getting enough speed, and hearing the transmission basically screaming.

I know Iím not the first to have this issue and I understand itís normal for every bus to be a little slow, but for safetyís sake Iím looking for ways to get about 10 more mph out of this thing, and maybe a little more power going up hills.

My bus is a 1988 GMC Bluebird, with the 8 CYL 8.2L Detroit Diesel ďfuel pincherĒ engine. Mine is naturally aspirated (not turbocharged) and gets about 165 horsepower at 3,000 RPM.

Iíve been trying to find info on the transmission all day with no luck. Iíve been told itís an Allison transmission, but at this point I donít know what the gear ratios are.

Obviously this is not a bus created with speed/power in mind, but since Iím having safety concerns, I want to see what my options are in terms of engine/transmission/differential upgrades.

So my question is this:

If I had a budget of around $2,000-3,000, what improvement(s) would be the best use of my money to give this thing more power?

Feeling a little bummed since I put 2+ years of hard work and TLC into this bus and I donít feel safe driving it with its current capabilities.
So any and all input/thoughts/ideas are very well appreciated.

Thanks!

Hers is a thread from back in 2016 that talks alot about your speed concerns.

this thread goes into some discussion about changing the rear gears and tire sizes. Hope you find something in this thread that is useful to you..

https://www.skoolie.net/forums/f36/8...sel-13996.html
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Old 03-02-2021, 08:32 AM   #7
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I'll have to agree with the fast that the 8.2L is not a desirable power plant. However, like the Cat 3208, they were produced in mass numbers and installed in about every application you can think of.


For the most part, there are two ways to go about accomplishing your desired result. Either throw more power and fuel at it, or reduce the need for more power and fuel. A bus going through the air at speed is like pushing a large barn wall. It's going to take a lot of power and fuel to do so. Using the words aerodynamic and bus in the same reply is laughable at best. However, there are a lot of ways that you can reduce the drag that air has your bus and allow it to travel through the air more efficiently. I would encourage you to investigate some of these before spending the money on a re-power. Then you can be better informed on your choices.


Team run smart's youtube channel link. Henry Albert is an expert on aerodynamics for OTR trucks. He loves sharing his expertise in the field of aerodynamics. There are many more channels on youtube with similar knowledge sharing as well as non-video websites. But basically they will tell you to keep as much air away from the underside of the bus as possible, keep the air attached to the sides of the bus as best as possible, then put the air back together at the back of the bus avoiding that low pressure vortex as best as you can.


If none of that is of any interest, that's fine. Then more fuel and power it is. However, instead of the HP rating and rpm, what is the torque rating and rpm? That is what you really want to be looking at for gear ratios etc. Most loaded trucks put their 4 ways on when ascending a hill on the freeways. Many also when descending that hill. It's good that you acknowledge the safety aspect of like speed merging and driving. That is not only a safety observation, but also a culture perception and image issue.


Going with the more power idea, IMO, the 8.2 is not worth spending any money on performance components if any are even available. So a re-power would be about your only choice. Diesel or Gas is the next question. Diesel would be able to make better use of the already installed peripherals. Though mounting brackets would need sourced.

If going gas, I personally would wait for a Triton V10 over all else. A complete vehicle purchase would be best.

Before any of that should take place, a set of math equations should be solved first with regards to gear ratios and engine heat removal. The bus likely has all the air flow needed though the grill, but still, it should be looked into.


In My Opinion.
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Old 03-02-2021, 09:04 AM   #8
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silvermachine, Please tell us more. How heavy is your bus, how fast do you want to drive it on the highway, how steep is the hill you go up in other words 6% 4% and how fast do you want to go up the hill. And what kind of fuel mileage do you want to get on the highway?
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Old 03-02-2021, 11:43 AM   #9
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Another option I hadn't thought of earlier... If you're handy. I have heard of 5.7L Oldsmodiesels being fitted back to gas, so I wonder if suitable pistons and other mods could make a fire-breathing gasser out of the 8.2L? Cost-effectiveness might negate it however. And I wonder if there is even a suitable piston available.

In addition to lower-compression pistons, the injection pump, lines and injectors would have to be swapped for an ignition distributor, wires and spark plugs. Carburetor or throttle-body-injection system would have to be adapted to the 8.2's intake opening.
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Old 03-02-2021, 11:52 AM   #10
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No. The 8.2 did not have an injection pump. It used unit injectors that were camshaft operated. Just like the 53, 71 and 92 series. Its closest cousin was the 6.2 / 6.5 it had an open deck with fused cylinder bores. No liners. These engines were used a lot in the oil fields for generators, pumps, shaker units and other uses.
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Old 03-02-2021, 11:57 AM   #11
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No. The 8.2 did not have an injection pump. It used unit injectors that were camshaft operated. Just like the 53, 71 and 92 series. Its closest cousin was the 6.2 / 6.5 it had an open deck with fused cylinder bores. No liners.
Ah. I've never seen one up close and personal, I figured the 6.2 was more or less based on the 8.2, being that they were both four-cycle. So that's out, and I learned something today.
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Old 03-02-2021, 12:02 PM   #12
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Originally Posted by s2mikon View Post
silvermachine, Please tell us more. How heavy is your bus, how fast do you want to drive it on the highway, how steep is the hill you go up in other words 6% 4% and how fast do you want to go up the hill. And what kind of fuel mileage do you want to get on the highway?
So for the weight- itís about 14.5 tons. Itís not a full size bus, just about 25 ft long. The mountain I live on is about 6.5% grade on average for a gain of about 2,000 ft.

Currently the bus only goes 30 mph tops up that hill and thatís with the pedal floored and the engine/trans screaming. It tends to heat up quite a bit too. In terms of fuel economy, Iím just looking to get whatever the average is.

Iím not really looking for engine upgrades, as I know the 8.2 is essentially just a noisy brick. Itís hard to find parts for, anyway.

So based on what everyone has said, Iím looking to swap the engine/trans for something more powerful.

Iíve seen a few good options in terms of a gas engine swap, any ideas for a diesel?

And if anyone has or knows a good deal on a compatible engine/trans, please send it my way!
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Old 03-02-2021, 12:23 PM   #13
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Ok, 29k is heavy and 6.5% is steep. How fast do you want to go up that hill? 45? 55? And how fast do you want to top out on highway?
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Old 03-02-2021, 12:34 PM   #14
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Looking to get up to 70-75 mph top speed on the highway about at least 40-45 mph up a 6.5% grade hill.
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Old 03-02-2021, 12:45 PM   #15
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Go to the link listed here and look at the charts and compare what you have now 165 hp with a much larger engine.

https://beaveramb.org/wp-content/upl...formance-1.pdf

I have used the above charts to plot 3 bus conversions and found them to be very close.
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Old 03-02-2021, 01:00 PM   #16
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29k sounds like GVWR, not empty weight... Has OP actually weighed their bus?
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Old 03-02-2021, 01:07 PM   #17
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CW, You should take the PDF from the link above and add it your other suggested reading. It would be a great addition to the new skoolies or those that think they can get car performance.
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Old 03-02-2021, 01:18 PM   #18
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CW, You should take the PDF from the link above and add it your other suggested reading. It would be a great addition to the new skoolies or those that think they can get car performance.
Only so much room in my sig per site rules, unfortunately. I think OP has somewhat obtainable ideas, but I think they're way overestimating their weight. 29k? An empty semi trailer attached to a road tractor weighs about 35,500 with full fuel tanks that add about 1700 lbs of fuel when full. No way a skoolie conversion weighs even close to that.
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Old 03-02-2021, 01:20 PM   #19
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Back in the day. A lot of 8.2's were swapped with 3208t cats, but they're still only 215 hp or so, and aren't really any more common then a 8.2 is now a days. You could swap in a t444e and gain a little more part availability, but you still would be limited by 230 or so HP.

Any swap to an inline 6 would not likely fit, as it would require a dog house on the inside that you would have to source or build.
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Old 03-02-2021, 01:21 PM   #20
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Mine is 30K. Weighed on a certified scale. So who knows.
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