o/d lockup not working when transmissions warm

[nhawks]

i have a 97 sport with 4.0 ohv and 5r55e when i bought it it wouldnt lock up the torque convertor in 4th or 5th. i replaced the valve body gasket cleaned the valve body and tested the solenoids which all checked out. after that it still didnt want to engage tc lockup all the time. i replaced the overdrive drum speed sensor and output shaft speed sensor. and now it will engage lockup for about the first 10-15 minutes. so if ive been driving city for 10-15min at one point it will decide to not engage lockup after having to come out of lockup (hit the brakes, slow down or stop)and o/d off light starts flashing after driving with no lockup. same goes for highway as long as i stay in lockup its fine. but once its been driving for a while and i have to come out of lock up (speed up slow down hit the brakes etc) it wont go back to lockup and o/d off flashes after driving with no lockup. if i let it sit for a while and then clear the computer it starts the process over again. i have a code reader and its not pulling a code while the light is flashing. it does read transmission codes because ive puled some in the past.

at this point im completely stumped so any help or ideas/thoughts are appreciated

 

[PopRichie77]

You probably have to much internal leakage due to one or more worn seals or a cracked center support in the seal area. Which results in not enough pressure left to activate the tc reg valve.

 

[drdoom]

I'm with Pop, something hydraulic possibly...get the codes pulled with a pro level scanner if you have the od off light flashing.

 

[drdoom]

Post up the code.

 

[PopRichie77]

drdoom is correct get the code if possible.