4L70E no TCC lockup
4L70E no TCC lockup Vehicle is a 2006 Trailblazer SS with headers and a small cam. I bought the vehicle for a steal from a friend as 3rd and 4th gear were gone. Went through the transmission using one of Dana's kits and added a Circle D 265mm 2800 triple disc converter. First time doing anything with an automatic transmission and I was very glad that I have 4 forward and 1 reverse gear that work great. Shifts are fast and it behaves very well, with one exception. The converter will not lock up. I tried using HPTuners scanner commands to lock it and nothing happens.
I know the O-ring on the shaft is good and new, I replaced the factory TCC valve with the TransGo unit that has a screw in it and has to be pushed in and out per instructions. Replaced the boost valve in the pump and all the other parts that were included in the kit. I replaced all the solenoids in the transmission with the exception of the TCC solenoid that is hardwired into the harness as I re-used that.
With the vehicle off and the key on, using the Scanner, when I command shift solenoids A and B I can hear them click, but when I command the TCC I cannot hear anything. Is that normal?
I know the O-ring on the shaft is good and new, I replaced the factory TCC valve with the TransGo unit that has a screw in it and has to be pushed in and out per instructions. Replaced the boost valve in the pump and all the other parts that were included in the kit. I replaced all the solenoids in the transmission with the exception of the TCC solenoid that is hardwired into the harness as I re-used that.
With the vehicle off and the key on, using the Scanner, when I command shift solenoids A and B I can hear them click, but when I command the TCC I cannot hear anything. Is that normal?
TECH Junkie
Joined: Dec 2012
Posts: 3,615
Likes: 1,327
From: Iowa
Tough to hear solenoids click. I don't particularly care for that as a good test but it's better than nothing
There is a very small orifice in the pump that supplies TCC solenoid with signal oil off the converter feed circuit.
If that orifice has debris in it and is plugged you will have a no lockup symptom
I'd verify the TCC reg valve isn't sticky. and the TCC Control valve in the pump is also freemoving.
Another diagnostic you can do is to put a checkball in the snout of the TCC solenoid. This will block it closed (same as if solenoid was ON)
When you start the vehicle it will idle in park/neutral
If you put it in gear, if the converter is locked, it should stall the engine.
This isn't the best for the converter so it wouldn't be my first recommendation.
There is a very small orifice in the pump that supplies TCC solenoid with signal oil off the converter feed circuit.
If that orifice has debris in it and is plugged you will have a no lockup symptom
I'd verify the TCC reg valve isn't sticky. and the TCC Control valve in the pump is also freemoving.
Another diagnostic you can do is to put a checkball in the snout of the TCC solenoid. This will block it closed (same as if solenoid was ON)
When you start the vehicle it will idle in park/neutral
If you put it in gear, if the converter is locked, it should stall the engine.
This isn't the best for the converter so it wouldn't be my first recommendation.
Tough to hear solenoids click. I don't particularly care for that as a good test but it's better than nothing
There is a very small orifice in the pump that supplies TCC solenoid with signal oil off the converter feed circuit.
If that orifice has debris in it and is plugged you will have a no lockup symptom
I'd verify the TCC reg valve isn't sticky. and the TCC Control valve in the pump is also freemoving.
Another diagnostic you can do is to put a checkball in the snout of the TCC solenoid. This will block it closed (same as if solenoid was ON)
When you start the vehicle it will idle in park/neutral
If you put it in gear, if the converter is locked, it should stall the engine.
This isn't the best for the converter so it wouldn't be my first recommendation.
There is a very small orifice in the pump that supplies TCC solenoid with signal oil off the converter feed circuit.
If that orifice has debris in it and is plugged you will have a no lockup symptom
I'd verify the TCC reg valve isn't sticky. and the TCC Control valve in the pump is also freemoving.
Another diagnostic you can do is to put a checkball in the snout of the TCC solenoid. This will block it closed (same as if solenoid was ON)
When you start the vehicle it will idle in park/neutral
If you put it in gear, if the converter is locked, it should stall the engine.
This isn't the best for the converter so it wouldn't be my first recommendation.
If it does pass the test I'll proceed with the suggestions you have posted above.
Thanks!
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Even if the old one shows continuity, it might be simplest to just replace the TCC solenoid which is available separate from the harness and is easy to splice in. Yours is likely already 18 years old and could be clogged with debris or deformed.
Finally got around to replacing the lockup solenoid. that did it! The old one was broken, the plastic part was not really attached to the metal part anymore.
Bow i have firm amd positive lockup. Just wanted to update with the solution.
Bow i have firm amd positive lockup. Just wanted to update with the solution.
