04 lb7 stuck in third, with no reverse?

[Sirrobbythe5th]

Alright so heres the deal, Ive got an 04 LB7 and other than my transfer case slipping when i get really stuck. Ive never had drive train issues until today.
I was going up a mile long 8% grade hill really going at it (I've gotten trans slip cautions on my tuner going up it before). And I had a hard down shift, followed by check engine light. I got to a stop and when I went to pull away and it accelerated extremely slowly, got up to about 55-65mph at around 2k rpm. So i assume its stuck in 3rd. Going from park into drive it smacks.
It won't go into 1,2,3 nor will it go into reverse AT ALL.
My tuner is reading "P0700" (generic bullshit code)
and the dash read out is saying "range shift inhibited"

Im hoping it something as simple as the torque converter...any ideas?

 

[ChrisPerry]

Scan it with a good scanner. You NEED the actual code or you can't diagnose an Allison.

 

[Cakes]

It would be cool if it were something simple, however, last time I saw this happen it cost me the price of a PPE Stage 4 trans kit.

Kinda sounds like you're used to getting into it, with it being tuned and all, so with that in mind it might just actually be toast.

 

[Sirrobbythe5th]

Ive seen somewhere that it could just be in "limp" mode?
And anyone recommend a good scanner for the tcm?

 

[2004LB7]

A GM Tech 2 is probably as good as it gets for the codes but that costs some coin. Could always just take it to the dealer but they will charge too.

I have used Pep Boys before. seemed like they had the tools and didn't charge anything. or better yet, take it to your local reputable Allison builder and have them make the problem permanently go away :rofl:

 

[Sirrobbythe5th]

Ok update here.... went out this morning checked the fluid. The fluid is gorgeous and properly filled
Started her up, let her warm up and she's driving fine and shifting into all gears. Monitored slip on my display and it wasn't slipping at all. However the P0700 code is still there and when I would clear it, it would come back. Any ideas?
I have yet to take it somewhere to have someone plug into it tho

 

[Awenta]

Check the round plug in the back of the transmission. See if it's full of fluid.

Need that code though


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[Sirrobbythe5th]

Round plug? I think I know what your talking about,,,, its on the RH side about the pan? What is it!?

 

[2004LB7]

it is the connection that all of the electrical gizmos come through to make its way to the TCM. it has been known that if it is leaking trans fluid into the connector weird stuff can happen. cleaning it out and seeing if the problem persists can help to determine if the trans has a major issue or a minor one that is easy to fix

 

[Awenta]

If that's unplugged or not making a connection it will default to third gear


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[Sirrobbythe5th]

Do I need to be concerned with fluid draining out when I pull the sensor do dad thingy?
Does anyone have a picture or anything just to ensure I'm pulling out the right part