Need help.. outta patience.. outta ideas..

[Yaryan92]

02 lb7. Built trans. Efi live. 240k. 6 inch lift. 37s.
When I'm slowing down for a stop sign or to turn and my truck goes to shift from 2nd to 1st it will randomly slam into first and the abs will engage. Also when truck has sat overnight and the colder the worse it is. When you first shift into drive, won't do it into reverse it will slam into gear. But after that it's fine. Trucks shifts and drives great beside those two issues. So far fluid and filters have been changed. No codes. Checked all wheel speed sensors and connections. Cleaned grounds. Data streamed wheel speed with no issues. Changed ect sensor. I'm at a loss. Shop that did trans 15k ago keeps saying its electrical outside of the trans. Or it has adaptation issues and needs wired for constant power. Please help! The harsh down shift is scary when towing. Also all new u joints and greased splines

 

[2004LB7]

What is your truck tire sized programmed in as?

 

[Ron Nielson]

Shop that did trans 15k ago keeps saying its electrical outside of the trans. Or it has adaptation issues and needs wired for constant power.

It would be nice if that shop would give you some more information and suggestions as to what your problem might be. And what do you understand 'needs wired for constant power' to mean?? What needs to be wired?

 

[Yaryan92]

It set for the 37s. Has been for 3 years and was never an issue. Problems started couple months after the trans was done. And continues to get worse. The slam shift with abs was super random. Now it will do it almost every time you stop... they said it may need wired like the bigger Allison's are? A constant 12v not just ignition power..

 

[OregonDMAX]

It's in the trans, they just don't know it or don't want to admit it.

 

[DAVe3283]

It's in the trans, they just don't know it or don't want to admit it.

X2


My truck had a hard 2 --> 1 shift when cold on the latest build. The shop said one of the clutch pack tolerances was set super tight, and that it should adapt it out, but if not, bring it back and they'd loosen up that pack. I forget which pack, because in my case, it did learn and shifts fine now. Sounds like yours isn't able to adapt out the tolerance, so the trans will probably have to come back apart.

My trans shop has also claimed that re-wiring the power to the TCM helps with shifts, but I am not sure I buy that. The power pins they say to add are internally connected to the existing power pins, so it wouldn't do anything, IMO.

You might talk to the trans shop and ask them if they added the additional power pins, and it didn't solve the issue, they woiuldn't charge you for it, right? I bet they change their tune.

 

[Mike L.]

Ignition power is 12V.

 

[Bdsankey]

I fail to see how a constant 12V source helps the TCM shift better. It is a keyed 12V source so as long as the connections/wire are in good health it gets the same power either way. The TCM sitting powered up won't help it magically shift better.

 

[Yaryan92]

I guess their idea is the truck is forgetting with the voltage drop?? They said if theres no codes then its not in the trans.. I have yet to get any code even with the back to back 2-1 bang shift with abs engage... I did notice when data logging that " engine torque" would spike from 1000 to 48000. I'm know the basics with scan tools so idk if that's normal or not. Or is there something I can watch for while hooked up to say hey this thing is messed up? I really don't have time to drive to Boise for it to sit at the shop. Any good shops in central oregon? Maybe that could give me some back up?

 

[Bdsankey]

I guess their idea is the truck is forgetting with the voltage drop?? They said if theres no codes then its not in the trans.. I have yet to get any code even with the back to back 2-1 bang shift with abs engage... I did notice when data logging that " engine torque" would spike from 1000 to 48000. I'm know the basics with scan tools so idk if that's normal or not. Or is there something I can watch for while hooked up to say hey this thing is messed up? I really don't have time to drive to Boise for it to sit at the shop. Any good shops in central oregon? Maybe that could give me some back up?

Adaptation is a stored value that a power cycle will not remove, it must be actually told to reset/forget them. You won't always have a code for harsh shifts.


Has this issue happened since it was put in or is it a recent development?

 

[Yaryan92]

It did it since put it.. but I would rarely ever happen at first... I took the truck back to have a leak fixed and the hard shift into drive and 2-1 shift fixed.. Thats when the constant 12v came up.. but after they looked at it they said it didn't need the constant power.. It has progressed more and more every time I drive. It went from once a month to almost every time I stop..

 

[Bdsankey]

It did it since put it.. but I would rarely ever happen at first... I took the truck back to have a leak fixed and the hard shift into drive and 2-1 shift fixed.. Thats when the constant 12v came up.. but after they looked at it they said it didn't need the constant power.. It has progressed more and more every time I drive. It went from once a month to almost every time I stop..

If the trans is under warranty still take it back and tell them to fix it. It's in the trans.

 

[Yaryan92]

I'll call then today and see what they have to say!

 

[Yaryan92]

Losing voltage to a trim solenoid? They said they would call a shop local to me...