TH350 Trans Experts – need help.

[K5_Fla]

I have a TH350c with the lock up switch. I have only had this trans for a few months. Trans works great.. only problem is when everything gets real warm.. the lock up starts unlocking and locking on its own. Again, only does this after 20 miles of driving (same constant highway speed) when everything is real hot.

I replaced the toggle inside the truck and the wire to the switch.. no help.

So.. I’m going to replace the vacuum switch and the solenoid. My question is.. the vacuum switch I have now is 48 psi. Should I get a lower psi switch ??maybe this is my issue, the psi at 48 is too high? I was thinking a 40 or 44 psi switch.

Here are some pic of what I have now… BTW.. I also noticed cracks in the wire to the solenoid...

 

[zombie1969]

The cracks aren't really a concern unless they were bad enough they are shorting out.You might want to install a temp gauge because a cooler might be needed if you don't have one.Heat has a big affect on how oil performs verify what it running and go from there with the switch.