Allison Shifting Problems

Shawn T · October 6, 2007

My brother owns my previous truck (03 Dmax/allison LB7). When he accelarates to merge on a highway or just run to the next light, the tranny will not upshift unless you just feather the throttle. If he he accelerates medium to hard it will just rev to red-line and not up shift until he lets off on the throttle. It just started the other day, and does it in every gear. If he babies it up to 3rd and then accerlates, it won't shift to 4th. It only has 70,000 miles on it, so it should be covered under warranty. Are these symptoms of a failing tranny? I would appreciate some info, so he can explain to the dealer what he thinks the problem may be

99silverado1500 · October 6, 2007

Never heard of that, my fathers LBZ if you stomp on it to pass on a highway you gotta pucker your cheeks, because it takes 4 seconds for it to finally go. Thats the only quirk i know of on a duramax. Trans may have problems with the servo maybe, best bet is to take it in and see what is really wrong, might have thrown a trans code.

StoneyPgh · October 6, 2007

Unusual . . . . . the Allison transmissions are nearly bullet proof.

I'd be interested in what kind of duty the truck has experienced and also,

what the transmission service record is concerning oil and filter changes.

Shawn T · October 6, 2007

Unusual . . . . . the Allison transmissions are nearly bullet proof.

I'd be interested in what kind of duty the truck has experienced and also,

what the transmission service record is concerning oil and filter changes.

Pretty much babied it's whole life. I put 52K on it, he has the last 18k miles. Just pulling camp trailers occasionally. Tranny filter change at 50k by me. Very good life for a truck, that's why he is so concerned. Any ideas?

BigJayDogg3 · October 6, 2007

This isn't helping you, but is this the 5 speed or the 6 speed ally trans?d

Bobslob · October 6, 2007

This isn't helping you, but is this the 5 speed or the 6 speed ally trans?d

If its an 03' then its a 5 speed.

Has it been chipped? If so you may have "limped" it.

That is when the tranny goes it to a safe mode and it wont upshift unless you pull over and shut it down and then restart it. Plus it gets easier to too every time because the clutches just get weaker and weaker.

Shawn T · October 6, 2007

Never chipped. Completely stock and no hard pulling. Shouldn't have ever thought about going into limp mode. I am aware of all of the issues stemming from that. I'm just looking for an answer to my original question.