Duramax/Allison

[lloyd]

We were talking at work today about my bus, MCI 5A, and one guy said have I ever thought of installing a Duramax with the Allison trans from a Chevy pickup. We are not sure if the trans would handle the weight of the bus, the engine probably has as much HP and torque as the 8V71. Has anyone out there have any information on this issue. It would defiantly fit, but would it stand up over time? What does a MCI 5 that has been converted weigh?
Lloyd

[Jerry32]

What is the difference between the bus and pulling a large 5r trailer? They made motorhomes with the 6.5 pickup engine in them and a gm auto tranny Jerry

[wrench]

 I would check for space with the duramax 7.6L from a medium duty isuzu or chevy 8500, more torque.  FWIW
                  wrench

[tekebird]

Difference.

Meduim Duty engine vs a heavy Duty engine

[edroelle]

THe Duramax and Allison are a great combination.  Before I retired from GM, I validated those units. 

You do NOT want to use those for you coach though.  As Tekebird said, "Meduim Duty engine vs a heavy Duty engine".

Ed Roelle
Flint, MI

[Hartley]

Don't forget all the electronics needed to run the combination. There is almost as much wiring as there is engine and transmission.

You would also need custom programming to keep from twisting the rotating parts out of the engine and transmission if you did put one in. The problem would be getting enough torque out of the combo to even come close to what a stock 8V71 puts out naturally.

Other than that it probably would work if you had the time, money and technical knowhow. There have been wilder things done...

Dave....

[Ednj]

[TomC]

Lloyd- Being a Freightliner new truck salesman, I can tell you that the Allison 1000 series used in the pickup is a unique transmission.  First off it has a maximum rating of 19,500gvw, of which your bus weighs more.  Also it has a special programming that keeps the torque converter from locking up until 4th gear for smoother operation.  When in tow mode, it will lock up in 2nd like all other transmissions.  The highest rated of the small case 1000/2000 series Allisons is the 2500 that is rated up to 660lb/ft torque (520lb/ft torque in 1st and 2nd, then the computer allows the engine to open up to the 660lb/ft torque in 3rd through 6th) and 33,000lb. And the most torque the Duramax PU engine puts out is around the 660lb/ft mark.  Compare those figures to a 8V-71N with N65 injectors that puts out 300hp and 800lb/ft torque very effortlessly, and I think you'd see that you wouldn't be very pleased with the performance from the Duramax/Allison 1000.

For more power on the 5, you could turbo the 8V-71-and I can tell you from personal experience, it really wakes up the 8V-71 to make it an enjoyable bus to drive.  Or switch to the 6V-92TA.  But at this point, I believe that any engine switch should not include the Detroit 2 strokers (as much as I like them) since they are only going to get more and more scarce and harder to find people to work on them.  Engines that would be suitable (none from pickups) would be the Caterpillar 3126/C7 at 330hp and 860lb/ft; Caterpillar C9 at 350hp and 1100lb/ft; International DT466 at 300hp and 860lb/ft; Mercedes-Benz 900 engine with 330hp and 1000lb/ft; Cummins 8.3/ISC up to 330hp and 1000lb/ft; Cummins ISL up to 400hp and 1200lb/ft torque (my choice); and the Detroit Series 50 at 350hp and 1150lb/ft torque-but it is very tall and about 500lb heavier than the other engines.  All could use the Allison 3000 series 6 spd transmission, with the length being about the same as the 8V-71 and transmission. 

Highly recommend none of the pickup engines be used.  We have just too much weight for the engines and they would be very short lived in a pumped up form to get enough power from them.  The medium sized engines from straight trucks (think U-haul) are the size that would work great.  They have a projected life of 350,000- 500,000mile, or about the same as the 2 strokers, and will get 2-4mpg better.  Good Luck, TomC

[lloyd]

Thanks for all the input, I figured it would not handle the weight of the bus. If a person turbo charged the 8V71 do the piston have to be changed?
Lloyd

[tekebird]

pistons and a few other things too IIRC

[TomC]

I have 18.7 to one NA pistons and kept the turbo boost to around 15psi.  My pistons are of the two piece design and have the tighter transit style rings to with stand the extra pressure from turboing.  Granted I haven't driven many miles, but no problems yet.  If you want to go higher than the 75 injector with full turbo boost, which is around 25 psi then you should change to the 17.0 to one turbo pistons. I also had a bypass valve blower installed.   Good Luck, TomC

[NJT5047]

Wrecked Class A diesel pushers are a good resource for engine and transmission combos. 
300-350 HP (and more) 6 cylinder  8L Cats and Cummins with Allison autos are all over.  They bring good prices, but can be found complete with wiring harness, dash, ECMS etc, (as Dr. Dave sez, and he ain't lying, there's a good bit of electronics with these engines and you better get it all when scavenging) in RV recyclers. 
There's a large salvager in Liberty, NC.  Amazing what he has piled up over there.   
If doing a conversion such as this, you may want to buy the whole donor and park it next to your bus.  You'll definitely want to use the engine/trans as a package.  Getting the electronics to work separately would get really expensive.
I once saw a 6Bt Cummins from a Dodge pickup in a MC5 bus.  It was not the ideal item.  It was slow, screamed at high RPM down the highway.  Still, he drove it, and may still be driving it, without any major issues.  Be OK in the flats.
JR