Allison 6 Speed GMC 401

[WE7X]

For something like 15 years, I have had an Allison AT from a 6500 or 7500 chassis. Would that likely be an MT40? I know I received a cable shifter assembly with it, that is about 25 feet too short for my rear engine configuration.
If I recall correctly, I was told it would have been a 5 speed, but I am not sure. Were they five speed, or six?

The plan back then, was to put it into my RM7500 'Motorhome', along with a 478M; to replace my 401M and the 5x2 Manual transmission. No progress yet, on that plan.
Rod J
Issaquah, WA

[tommr]

Flexplate assembly from Bendtsens. consists of a GM factory plate from an old MT40 application. Bob shaved the face and drilled it for a factory Allison adapter ring. Then he machined a center pilot assembly to center the torque converter hub into the center of the plate. All very nice and very precise. fits like a glove. Don't think anybody else on the planet had these parts and the exp on the GMC V6. Glad I found him. Driveshaft is being built this week. All new Spicer yokes, tubes and axle companion flange. Gonna be a nice piece.

[BobBray]

That's a very nice Flxible (yes, I spelled it right) Clipper you have there! Many of those were built with Buick straight 8 engines and were converted to GMC V-6 power in the 60's. I have a friend with a Clipper that has a 478 in it. Good luck, hope you get it back on the road soon. It's a light bus and it should really fly.

[tommr]

Yes ours had a 320 Buick inline 8 originally. It was converted to the V6 in 1971. Gonna be interesting to see how well it pulls 5th. The 478 would be unbelievable in a Flx. Tom

[tommr]

youtube.com/watch?v=itSs8SYvpbM Might have posted this before.

[abus319]

I have to admit there are some big gaps in my mechanical knowledge and automatics definitely fall into that category.
I have been puzzling over the bolt/ hole setup on the center pilot assembly. I assume that the 6 countersunk holes are for the crank thru bolts. Are the other 6 holes threaded, I can't tell for certain?
h

[tommr]

correct those are thru bolts to the crank. the other holes are threaded and not used for this app. Bob must have been repurposing something he had in inventory. thx.

[abus319]

Cant wait to see pics of your progress.

[tommr]

Did 4,000 miles in 23 days. the 401 needed 2 qts of oil and aside from a load of separated gas ran great. The Allison 1000 operated perfectly. 60 mph is 2100 rpm instead of 2800 rpm with the non synchro non overdrive 4 spd Spicer. Got an astounding high of 9.5 mpg on mostly flat highway only runs of 350 miles. Highway only was 8 mpg with the old trans. Not the jump I thought I would get with the rpm reduction but even the prior 8 was very good. Combined highway/city was low 7s. Used the biggest Griffin trans cooler they make and never ran more than 170 degrees. The 401 is still very able but slow in the big hills. pulled a crazy steep hill up to an overlook in 1st gear at 2400 rpm. The guy behind us couldn't believe we made it. The bus felt like it could have pulled it all day as long as youre not in a hurry. Tom

[turbobill]

Nothing wrong with the hill climbing ability that a turbocharger won't fix! That's the only device that makes diesels powerful.