Allison 6 Speed GMC 401
 

2006 6 speed Allison from a GMC Kodiak RV bolted to 401M engine. Hows that for keeping it all GMC? Will be programmed as a standalone to operate as a 5 speed. Bendtsens is finishing the flexplate up this week. driveshaft is at the driveshaft shop. Should be driving this month. Junkyard transmission on a 50 year old motor in an almost 70 year old bus. bet that's never been done before.

Re: Allison 6 Speed GMC 401
 

If it's a 6 speed, how come you can only use 5 gears?

Re: Allison 6 Speed GMC 401
 

5th and 6th are both overdrive. 6th gear would only be usable for speeds we don't travel and it is more $ to make 6th gear work in standalone. 6th gear is more suited to electronic engines.

Re: Allison 6 Speed GMC 401
 

Years ago I picked up a 401 with an Allison MT40 6 speed attached. The engine was junk, but I had the 6 speed rebuilt and still have it in storage.

Thinking then I'd never find a good 478 (that took another 10 years) I scrapped the componennts to bolt the 6 speed to the GMC engine.

Re: Allison 6 Speed GMC 401
 

Nice!
Is a control module required for stand-alone operation?
If you don't mind, how much was the flex plate?
hh

Re: Allison 6 Speed GMC 401
 

The MT40 was a non overdrive trans. cast iron case I believe and was unbelievably sturdy in its day. Its interesting to see how this aluminum case 1000 trans with overdrive and weighing about 200 lbs less has eclipsed the 40. handles probably double the torque and HP input. Yes a factory TCU is required along with the standalone harness and a linkage mounted TPS. flexplate was $600 and includes bolts, torque converter spacer and a custom machined center hub pilot to keep the tc hub centered in the crank end bore. Bob is the man on these engine/trans conversion adapters and custom flexplates. has done a lot with the GMC V6 engine conversion to various automatics.

Re: Allison 6 Speed GMC 401
 

That'll be sweet! :thumbsup:

Re: Allison 6 Speed GMC 401
 

Thats interesting that the tps is the only input.
That not too bad on the price considering what you get.
I haven't been able to find a flywheel for my 478 yet so that might be an option.

Re: Allison 6 Speed GMC 401
 

Multiple cracks in the flywheel and a broken bellhousing pretty much left me no options for a transmission. being remotely shifted pretty much rules out any stickshift option. could probably spend $5k building new parts and repairing and freshening the clutch. and I would still have the obsolete 70 year old transmission setup that no replacement parts exist for. plus with the Allison will have much needed overdrive.

Re: Allison 6 Speed GMC 401
 

Sounds like a good choice to me. Im looking forward to seeing how it goes.