Alright gents got a question maybe some of you will have some ideas about the problem, I have a 98 f-body I just put a 96 4l80e in the car with a tci transbrake valve body kit with a yank 4000ss converter. The tranny was rebuilt and everything is new, when the car is cold I have reverse and the transbrake works but when the car is warmed up and at operating temp I lose reverse and the transbrake stops working, but 1-4 all work great and it shifts hard, just wondering if any of you guys have any ideas. Took it back to the tranny builder he changed the 2 solenoids on the transbrake thought it was fixed but still having the same problems tried the transbrake when the car was cooler and it worked but the converter flashed to 5k not 4K, converter seems to feel very loose as well

 

Turns out when warm (160 degrees or so) the trans is only seeing 100-120 psi in gear, back to the shop the trans goes.


Months have passed. The issue is just now being sorted out. Thanks to Hutch.
The transbrake/valvebody was leaking internally causing a loss of pressure which created all of the mentioned issues.