Allison jumping out of gear and down shifting

[PistolPete]

Hey Guys I am a new member and i have problem with a 2004 suburban with a LB7 and allision trans. Its jumping out of gear at highway speeds or sometimes down shifts. It never happens when driving around town always at speeds 70 or above. No one has been able to get any codes relating to this problem. I am wondering if anyone could lead me in the right direction. it has been to a dealer and private shop. Thanks for any info you may be able to give

 

[juddski88]

Some Allison files hunt for gears, I've noticed it most is 08 6sp but also one particular 04 5sp. If you Dont like it, find a very competitent tune writer who knows his way around the Allison TCM files too

 

[PistolPete]

does anyone know the best place in florida to take my truck to to have this trans problem figured out. I am in fort myers don't know of any that i have any confidence in working on allison transmissions

 

[paint94979]

Take it to Suncoast

 

[Mike L.]

When's the last time you changed your fuel filter?

 

[PistolPete]

Mike just had new injectors and airdog fuel system and new fuel filter installed two weeks ago. I had a fleese tap shifter installed about 5 weeks ago but it had jumped out of gear twice before that was installed and 4 or 5 times since it was installed. I don't know if this other symptom has anything to do with trans but when I accelerate from a stop after going about 10 feet there is a clunk almost like it has slop in rear end, but it never does it slowing down only from a complete stop. Rear end did have a lot of wear and was replaced 5 months ago. Rear end was rechecked and within tolerance. The play seems to be in trans when on a lift. Truck has about 180k

 

[juddski88]

I guess I am confused, is it going into Neutral? or is it downshifting? or is the converter randomly unlocking?

 

[JDub]

I changed my fuel filter Thursday and experienced similar unexpected downshifts while cruising town on Saturday. dash lights show the downshift and everything. have shift to neutral then back to drive??? not sure what to check, tcm harnesses are tight.

 

[tyrat]

My 2003 rclb 4x4 duramax is also doing this it has 340k and the trans shop cant figure it out it first started doing when pulling a trailer but has continued to do it with out trailer.