You guys gotta read this. It came from RV.net

 

?????? What else did they pull out of their hind ends?

 

What are they talkin about????

 

i think the tranny downshifts on tow/haul mode. they could be refering to it but i doubt that the tranny alone would stop the truck and trailer.

 

Thrust reverser sounds sorta like an exhaust brake.

At any rate, it's likely right next to the flux capacitor.
Those GM guys get all the cool toys.

 

I think to make that work you have to upgrade the flux capacitor & adjust the optional P38 modulator.

 

If I remember right, in popular mechanics they had something that GM was coming out with. It used compressed nitrogen or hyrdogen to slow down the main driveshaft via a air type motor. Then when you take off, it would recharge the tanks until it was needed.

Tranny alone, I don't think so, but anything can happen.

Jon

 

speaking of those upgrades, you know where I could find a good used one?? I don't want to spend that kind of money for a new P38 modulator, just doesn't make sense that a part the size of a nickel could cost $3000.

 

My brother tows a 5er with his 2003 Duramax/Allison. Tow/haul would not help much on Pacheco Pass, it was white knuckles and red brakes every time. He won't cross the Rockies to visit me. He installed a Banks exhaust brake and now it's almost as good as my CTD.

 

did you guys know that chuck norris' tears could cure cancer, to bad he never cries.

the allison is like chuck norris...it doesnt back down from anything

brett

 

Brett, I had heard that too, I think at the fire station.

 

i dont know what model allison they are talking about but i have heard of retarders on bigger trans units, mostly buses though?

 

That is pretty far fetched and I dont buy it.

But if you put tow/haul on (keeps the converter locked ALL the time, even thru shifts, all the way down to 20mph) and throw the ally in "1" it will slow the truck down much faster than you would think. When it does the 2-1 downshift at ~20-25mph it literally will throw you forward in the seat and bark the tires because 1st gear is so low. I have done it; with a trailer, throw it in "1"...the trans WILL bring the truck and trailer "confidently" down to 5mph, but definetly NOT in the short time stated there. It is not like any other auto trans in that it is impossible for it to "free wheel". It is always locked positively in gear. Think of it as a manual tranny with a torque converter in place of a clutch.

But even throwing it in 1 will not cause immediate downshifts that will rev the engine thru the roof. Once you move the shifter out of park, NOTHING happends in the ally valve body. It is all electronic. THe TCM will keep you from doing anything stupid, like 1st gear on the highway. You can even put the transmission in reverse on the highway; it just kicks into neutral. Its a great way to get rid of tailgaters tho, because when you put it in reverse on the highway and the trans goes into neutral, the reverse lights still come on. If you try to do a neutral drop it will bring the engine down to idle (even if you have the pedal floored), then go into drive, then go WOT. Also if you put it in neutral on the highway, it automatically rev-matches the engine to your curent speed so when you put it back in drive its seamless. It will downshift immediately from 5-4 as long as you are under ~100mph...then at ~65mph it will do a 4-3, etc etc...

It will slow you just about as fast as aggressive downshifting would on a manual trans.

But in reality on these trucks we are limited by tire grip. We are dealing with 7000+ pound hunks of steel that carry a huge amount of inertia, and no big brakes or amazing other things can overcome the laws of physics.......

just my oppinion

ben

 

they must have put some heavy duty springs in there for the kunuter valva

 

The bigger allison trans can be had with a hyd retarder.....untill you feel one work you will never understand!!!!!! Yeah its that good.