06 Allison going to neutral when hit bumps

[Lpzd]

Going down road with cruise on, hit bump trans goes to neutral, truck revs goes to limp . Code p7029.
Not sure where to start looking

 

[Awenta]

I'd be looking in the transfer case

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[Lpzd]

If cruise is off I can let off the throttle for a second and then keep on going.
It only "jumps out" for a second . If tcase was going to neutral wouldn't it be longer than that?

 

[$chultz38]

Does the check engine light come on? If so what are the code codes?

 

[Mike L.]

I would be watching turbine and output speed sensors first.

 

[Lpzd]

P0700 and p0729 are only two. Thanks any direction is appreciated. This is my first diesel with a auto.
Prefer manual but this truck was a amazing deal.

 

[CarolinaHD]

Possibly could be this?

Now dont think I'm stupid, well I kind of am but there is a place near me with a hump in the road sort of like you described but on flat ground not up hill. I can hit it under acceleration in high gear and it lightens the truck enough to spin the tires. At that speed I dont hear the tires spinning it feels like the truck goes into neutral and then back in gear. Maybe this is whats happening to your truck?

Landon
What you are describing is normal. When you lose traction the TCM will kick the Alli out of gear just the same as if your were at a stop in nuetral and brought the rpm's past 1200 and threw it in gear; it would do nothing. Just the tcm protecting the Alli.
Good call.:thumb:

http://duramaxdiesels.com/forum/showthread.php?t=26731&highlight=neutral+bump

 

[Lpzd]

Engine revs drastically when happens no loss of traction

 

[$chultz38]

Grab the output shaft and see how much play there is. If there is alot check the sensor for damage. The relector ring to sensor tolerance is close. If the output shaft hits the sensor it will do what you are talking about. If that is your problem the t case needs work!

 

[Lpzd]

Thanks for input just picked up the truck yesterday it has 226k miles so i fully expect some work needed. But only paid 6k for the truck stop that's ok.

 

[Lpzd]

Transfer case output is tight , going to replace all 3 sensors.

 

[Awenta]

Transfer case output is tight , going to replace all 3 sensors.

Why? Monitor them first

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[Lpzd]

I'm currently just using tourqe pro to check codes( only had truck 2 days) .
What do I need to use monitor them?

 

[Awenta]

Tech 2. Also think a v2 can read them.

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[Lpzd]

Thanks.

 

[Awenta]

Know anyone that's got one? What's your location, there might be someone close by

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[Lpzd]

Can't think of anyone with a v2 . I'll try the mechanics at work and see what they have .

 

[Lpzd]

Turns out out is the t case. In lock up input and turbine almost mirror eachother, 3-6 RPM difference.
Bringing rpm up against brakes, truck not moving at all.
Output shows varying rpm up to 120.

 

[Lpzd]

finally got transfer case back together . thank you for all of your input, I am finally liking my truck.