'94 5 speed manual tranny: will it mate to a Duramax?

[tehillah1]

I checked out the Lil Red Truck...wow! In the articles it mentions the TH400 and 4L80-E haveing the same bolt up patterns as the Allison Trannys. I'm assuming this means that the bell housing on my standard 5 speed would be the same also, though I don't want to be the beginning of the assumption when I purchase a Duramax and find out it ain't the same...Anyone have any info on this?

[More Power]

Yes, the Duramax has the very same transmission bellhousing bolt pattern as used by a 6.2/6.5 (as well as any other Chevy/GMC V-8). The TH400 and 4L80-E torque converter will also bolt right up to the Duramax flexplate.

The big question for you is, is there any sort of compatibility with the manual flywheel? I don't know. The Duramax manual trans flywheel is a lot different than that used on a 6.5.

Jim

[tehillah1]

Thanks, Jim. The experience and info you all share here is priceless. I'll do some homework on seeing if the manual is an option...I'd ultimately like to put the 6 speed Allison in this truck, but maybe I just wait and buy the whole rig...I'm kind of attached to the older body style and seeing what you have done with the '89 is pretty impressive.

[a5150nut]

I have been told there is a difference in the number of splines on the clutch disk and something is different going into the transfer case. Oh and 2 1/2 inches longer on the 6 speed.

[tehillah1]

I think the Allison size problems are workable, given what Jim has accomplished with his hot little '89...indeed one of the articles says that the older frame set ups have enough room. I'm wondering about the manual flywheel setup on the Duramax and if it will work, clutch assembly and all, and spline up to the 5 speed manual in my '94 K2500. Anyone have any details on this?

[GMCfourX4]

Just for the sake of argument, have you considered getting a 6-speed DMax with trans and t-case already attached? That would seem to be the easiest solution....

-Chris

[tehillah1]

Chris,
I sure have considered doing the whole enchilada. I have a strong manual 5speed in the truck now and have been pricing used Dmax engines in the $1800 to $6000 range. Adding the 6 speed Allison would certainly be the best of all worlds but I'd like to begin with the trans/transfer case and rear end I'm running if I can.

[GMCfourX4]

You can certainly use the rear-end you have. The 14-bolt FF is known as one of the strongest available on any light-duty truck. I was thinking it might be easier to modify the corssmember (if needed) and driveshafts than to try to get the DMax harness to work happily with your existing trans. The 6-speed manual trucks may hook up just fine, but if you want to switch to an auto, you would probably do well to get the whole mess together with the harness, rather than try to get it to work with your 5-speed (there could be issues getting the clutch working, even though the bellhousing will bolt up... ) then trying to get the auto later on. I personally would like to do a DMax/NV5600 swap (or even the ZF6) but I can't justify it with the way my 6.5 is running.

-Chris