Lbz transmission trouble

[coreyfatboy]

New to forum. My son bought a 2006 lbz efi live 60%injectors 66mm turbo billet internals. Drove it for a couple months then one day tranny started doing a quick slip clunk between 2nd and 3rd and then in 4th and 5th. Got a u0101 code checked the harness looked good thought it might be tcm. Bought new one took it to the dealer to flash and they said they couldn’t make communication with it. Took it to a friends shop and he was able to make communication but it was telling him that the tranny temp was -40deg and no 12volt power. Put the new tcm in and got same numbers. Tried to go thru the ecm but was locked out due to efi love I assume. I’ve been trying to figure this out for like 3 months and I’m at my wits end. Any suggestions would be great. Thanks

 

[Mike L.]

Your slip clunk could be a blown out C3 apply piston. Get a wiring diagram for the TCM and check voltage to the proper connectors. A Tech 2 would make checking things easier.

 

[coreyfatboy]

I’ve checked the power and ground pins they were good. How can I check the piston. There is no codes. I did pull the electrical plug on the back of transmission and it was full of tranny fluid. I have the pass thru plug on order

 

[joshd472]

only way to check it is to pull it out. I had a 1-2 clunk and he suggested I change the C2 piston, I did it and it worked. I had took the trans to 3-4 shops before that and they all said it needed a rebuild.

 

[coreyfatboy]

Would that cause hard downshifts also? I just believe it is an electrical problem with the info that is going thru the tcm. I pulled the pan last night and it looks great no metal or anything on magnet. It’s like it’s in limp mode or something. The pressures are jacked up like 175%. I’m wondering if it is something with the ecm but my mechanic is locked out of it because of efi live

 

[zakkb787]

Listen to mike. There’s no one on this planet that knows Allison’s like him.

 

[joshd472]

Yes mine would hang on the 1-2 up shift then slam into 2nd and on the 2-1 shift it would also throw you into the steering wheel. Fluids, temps, valve body, everything checked out great. Replaces the piston and the problem went away.

 

[snowman22]

Listen to mike. There’s no one on this planet that knows Allison’s like him.

Here's the best advice you will ever get! Other than Mike...

 

[coreyfatboy]

I will definitely try anything at this point. I’m not sure why I’m losing communication with tcm and I don’t have the problem every time. Would it throw a code if the piston went bad?

 

[joshd472]

Mine didn’t

 

[1TRIKHD]

Ive heard if you have fluid in the main wire harness plug, that can make the trans act up.

 

[coreyfatboy]

Ok so dropped the pan this weekend changed filters put new passthru connector in. Took it for a test drive does the same stuff. Drove about a 1/4 mile came to a stop went to take off and nothing. The indicator light under the prnd123 was blinking then went off. Turned truck off and restarted worked fine. Got u0101 code. Got back home and tried to pull up transmission temp and relearn on edge cts nothing there. WTF! It was there in the past. What the heck is going on?

 

[Burn Down]

Did you clean the truck side plug with electrical cleaner and blow it dry?

 

[coreyfatboy]

I cleaned it blew it out and cleaned it again and let it hang dry. After the drive I pulled the plug and it was dry. Another thing that was weird is that the edge went dead during the drive and when I got home I hooked my code reader up and it kept losing connection. I wonder if this has something to do with ecm

 

[Budneeds2beers]

These are all suggestions that might apply to this situation. I dont think this is going to be an easy fix. You are running back and forth second guessing yourself. I understand your fustration but MIKE L gave you great advice. I would start here and put in some work and post findings/codes. Glw this. I will one day be in your shoes on this same thing.

 

[rcr1978]

only way to check it is to pull it out. I had a 1-2 clunk and he suggested I change the C2 piston, I did it and it worked. I had took the trans to 3-4 shops before that and they all said it needed a rebuild.

Not second guessing you or trying to be a dick but i'm on this one the C2 is not applied during these shifts did you mean C4? C2 does nothing until 4th on and C1,C4,C5 are the only active ones during the 1-2 & 2-1. Also C2 piston has replaceable seals and C3/C4 pistons do not you just replace the whole thing . Was there anything viseably wrong with the C2 piston?

 

[coreyfatboy]

The truck was in the shop early this week and found the communication problem. Still shifting like crap. Took the efi live program out returned ecm to stock and re flashed the tcm. Shifts better for about ten minutes then starts slipping between 2-3 and 4-5 and hard downshift into 1st. Still no codes

 

[TheBac]

What was the communication problem?


Just my opinion, but with the mods to the engine you listed in your first post, Id lean toward the clutches being wiped out and the trans being toast. There are a lot of people out there that'll add every bolt-on they can to build engine power and yet never touch the trans and end up paying the price.

Only way to really find out is to pull the trans and tear it down and see what you can find.

 

[joshd472]

Not second guessing you or trying to be a dick but i'm on this one the C2 is not applied during these shifts did you mean C4? C2 does nothing until 4th on and C1,C4,C5 are the only active ones during the 1-2 & 2-1. Also C2 piston has replaceable seals and C3/C4 pistons do not you just replace the whole thing . Was there anything viseably wrong with the C2 piston?

I can’t remember honestly. Probably was the C4.

 

[torqued2dmax]

Are we talking about a stock transmission and converter ?