[shelyb987]

For the price of collecting all of the required parts, odds are good it would be cheaper to find a high mileage donor duramax vehicle and swap the engine, trans, and transfer case over to your 1500.....that being said, if you are dead set on the quad steer, I would say swap that running gear over to a duramax, but I am not 100% the quad steer axles are going to be strong enough to stand up to the low end torque abuse a duramax would put them through.

I wouldn't want a 4L80 behind a duramax unless you like rebuilding/replacing transmissions. The added weight of the truck, running gear, and the towing cabilities of the the 2500/3500HD trucks mandates the Allison transmission. The 4L80 didn't take the abuse the 6.5l could put out, and it was never put behind anything bigger than a 6.0L. The 4L80 is fine and dandy for small blocks, but big block gas engines (8.1L) and the diesels all got the Allison or the 6L90E.

 

[shelyb987]

Why did they put it behind the Duramax vans then?

It would work in my opinion......He said he could de tune the duramax so the trans would hold up....

GM does lots of things to keep costs down....the 4L80E is CHEAP to them (I used to build both the 4L's and the 6L's for GM and they pale in comparision to the build costs of the Allison), most of the people buying those cargo vans aren't looking to pay the $3k premium for the allison.

My bad......if he wants to detune the duramax to the tq. specs. of the gas motor he already has.....then YES....it will work.....I guess my stupid question is, why go through the trouble for 50ft. lbs more than the gas engine he already has, and a redline that is 2k rpm lower?

I like diesels....but if you fail to take advantage of the benefits of the Duramax (600+ ft lbs)....why bother?

IMHO the cost of detuning, and still having to beef up the 4L80 will outweigh the costs of getting a stock Allison to work right off the bat.

 

[shelyb987]

I am not 100% but I think the 6.0 only came with 4.10 gears. and with the 4L80 having an OD of 0.75 that makes the final effective ratio of 3.075

The 5 speed allison has a final ratio of 0.71 and the 6 speed 0.61. If I am correct, all Duramax equipped trucks came with 3.73 gears. The final drive ratio will be 2.65 and 2.23 respectively. Keeping the 4L80 with factory gears means a 16%~37% increase in RPM at any given speed. Not to mention the losses associated by having to rev. the engine higher before each gear shift (acceleration spread out over only 4 gears vs. 5 or 6).

If you are dead set on having your quadsteer pushed by a duramax I would say spend the money and time on getting the Allison working, or be prepared for a gear swap.....otherwise you are gonna have a detuned Dmax that probably gets off the line quick, but moves out of its efficient powerband on the highway.

But that is just my $0.02.....either way, I think a project of this size would be best done with a good donor....put the trucks side by side and see what you think will be easy to swap, what can be made to fit, and what simply can't make the transition.....let the hard parts dictate the project if you are really having doubts or concerns. I would imagine the quadsteer would be easier to swap into a duramax, but again, I would have concerns about the strength of those axles.