New to medium & heavy duty trucks - need information and advice on Allison transmission in a dump tr

If you have any trucks that have done a good long time job look at them. Tire size, axle ratio, engine, transmission etc. Try to duplicate that. If I were in your spot I would try to contact Allison directly.
What do they recommend but you have to fill in all the blanks.
I would stay away from all the new just came out on the market stuff. Let someone else experiment.

 

Your best information is going to come from the drivers that run those trucks every day. Pick a few of the more reliable ones and buy em lunch. Find out where the strengths and weaknesses' of your current equipment is from their prospective. Then do the same with a few of your mechanics. Do this with the folks who get dirty and you will have a much better idea of how the equipment functions in the field. You need to understand that before you start to make changes.

 

I do mechanic work and seen quit a few allisons.
The 2500 is a lighter duty compared to 3000 or 3500. They are good for road use but seem to wear prematurely with heavy off road use.
The 3000 close ratio is good for highway trucks, with good take off.
The 3500 wide ratio with deeper first helps with being off road or slow dumping operations.
I wouldn't consider a 2500 in dump, not heavy enough, and would stick to the 3500 on your 6.7 and maybe step up to 4500 series with 9 liter, not sure the 3500 can take the higher power power of 9 without big derate. Dealer should be able to help on horsepower settings and selection.
The allison does have 2 overdrives so I recommend buying setup that way, meaning get a lower rear ratio and where the second od is useful. Seen too many spec with just 1st overdrive and too high rear end for off road slow operation.

 

I think our company specs the 3500 RDS in our 6yd M2 dumps. It might be the 3000 however, I'd have to check the spec sheet the next time I get In one.

We use the 3000 in the rest of.our rigs, our smaller bucket trucks to our full size utility buckets (which is what I drive), our 2013s have the ISB engine, later ones have the ISC, and a handful of others have the more powerful ISL.

Come to think of it, they specced our Vactors with the 3000. And the 325hp ISB. Talk about a pig. Loaded up over 50k (max is 63k on that chassis) and it was slow...REALLY slow, like pedal to the floor trying to maintain 30mph up a grade. Not fun.

Rear gears are anywhere from 5.68 to 6.34. max out around 70mph.