Kerr

Hum.... Wonder if they changed that. There has to be a way to get around it. The let the diesel guy have 650lbtw tq...

npb4me

iTrader: (1)

I can tell the engine to give max hp and torque to the tranny, but if the TCM for the tranny says no, it won't let that happen. Talking with the dealer has confirmed some issues. They admit that the new 8.1 (496) doesn't have the hp and torque to push the power through the Allison and to the ground the way the Duramax does. They said it takes about 350 rwhp to get the Allison happy. We have a 02 GMC Sierra 3500 in our shop with the 8.1 and the 4L80E yesterday. Same truck as my dad, just different trannys, and the 02 out ran my dads truck every where we went. From a dead stop to passing on the freeway. It was a fun drive!! I tuned the 02, and had it smoking the tires, I did the same thing to my dads, and it wouldn't smoke the tires. So I think this kind shows that the Allison isn't a good match for a gas motor unless you have over 350rwhp.

02_2500avalanche

I don't know where you found an 02' seirra with a 4l80e and an 8.1 cause they never made them. The allison has been standard equipment on both the 8.1 and duramax since they were released in 2001. Only in the hd trucks could you get a 4l80e with a 6L, the only trannys you could get behind the 8.1 where the allison and zf 6 speed manual. The avalanche 2500's, suburban 2500's and 2500 vans could you get an 8.1 with a 4l80e....they could never fit the allison do to clearance issues on the trans tunnel.

Alex

npb4me

iTrader: (1)

By same truck as my dads I ment same setup, the 02 is a cab chassis with a box on the back. But it has the same engine, same gearing, and yes, it has a 4L80E in it. And the weight of each vehicle is within 300lbs of eachother.

Kerr

i wonder if the diesel programmers will let you over ride the TM on the trans of a gas truck? I know how you feel. our 60 is a slug. Brad has a 01 8100 with 3:73 gears and it will spinn 285-75-16 at will...

Be glad you dont have the 6 speed manual. we drove one of those and they suck ***** bad..

On the armada's and titans there is a wire you can unhook or cut to delete the TM on them.. Maybe gm did something like that? If he does not love the allison i guess you could dith it, get a 4L80E? Have you talked to whipple and see what they say? I mean if the computer is not letting power out do to the trans then how in the heck is whipple making 800lbtq?

npb4me

iTrader: (1)

I think Whipples dyno #'s came from a 4l80E trans. Might be wrong though. The Allision just wants power. You have to feed it power and torque to get it to the tires. Or it just eats it up and laughs at you.

ajt86

iTrader: (1)

you are going to loose some power with the allison, their internals are heavy. when i took my first one apart 2 years ago i was amazed at the first backing plate i took out- it weighed as much as some planetary sets ive pulled out in smaller transmissions.

but their should only be a little power loss, not so much as where you would feel it when you lay into it

tb8100

iTrader: (1)

my last truck was a CCLB w/ the 8.1/ally and was pretty ballsy for a stock truck. it would light up the tires from a dead stop at any given time. my current truck in its will not spin the tires period. not on a brake stand or anything. 1st gear ratio on the 80E is just too high....

I'm hoping after the headers, high flows, cat-back, cam, and stall, it will wake up. After 1st gear, it does great! Especially passing on the freeway and crap. does great.

02_2500avalanche

That cab and chasiss must be some kind of rare built truck. The allison eats up power but it is a far better tranny than the 4l80e do to gear ratio spread, pretty much exactly why I will be swapping out the 4l80e for the 6l90e from the new hd's.....a 2.48 first gear to a 4.10 is quite a difference never mind too extra over driven gears.

Alex

yurs78

you have to figure out how to get rid of the TM in the tranny. Nothing you do to the engine will matter one bit if you don't fix that. Ask the diesel guys they work with those things all the time. I remember a guy in the diesel section that ran a 12.9 with a CC diesel (06 LBZ) TUNE ONLY. He built up the tranny to hold to the power but that's all he did was tune the engine. That's smokin fast for a heavy pig like that.

I'm sure someone has figured it out. Just like everyone says the gear splits in the allison are way better and the thing will handle all the abuse that you can give it. Throw a great cam and some LT headers and you'll have a fricking BEAST. And you'll have a fraction invested vs. the whipple.