5R55E TCC problem

[PopRichie77]

I get flashing OD light. Code 0741, the torque locks up when cold but as soon as it warms up, not many miles, it wouldn't lock up. Trans has 125,000 miles and spent most of it's life pulling a 3800 pound trailer, which it did very well. I connected a volt meter to the computer side of the TCS, checked all wiring, replaced the TCS and the EPC both new, cleaned the valve body and change filter and trans fluid. The voltmeter tells me when the computer signals the TCS to activate and I can see by the tack if it did or not. Tried 2 valve bodies from Ebay, updated with new ford EPC relief and bonded plates still had the problem. Put a TransGo shift kit in the original and modified the plate per Sonnax, got some improvement but still had same problem. I then did some thing that I think should have done the opposite but it worked. I removed the small spring, there are 2, from the TCC solenoid regulator valve and replaced it with a lighter spring, one from the Cooler limit valve. After about 40 miles it still locks up but much slower. When it locks it will take full throttle with no slip, 4 or 5 gear. Looking for some insight on the spring change and why it improved the lock up? Also looking for a flow chart for the TCC circuit? A tech at Sonnax said the TCC seal on the front of the pump may be bad, I plan on replacing that next but won't be able to for several weeks, I do have the new type uncut seal ring.

 

[BrooklynBay]

Did you check the internal wiring harness?

 

[PopRichie77]

Yes, internal wiring checked ok, torque converter clutch can be applied any time hot or cold by grounding the computer side of the TCS and it locks up firmly. Also will stall the engine if applied in Drive while stationary with brake on. Line pressure is in spec 105 psi in Park or Neutral and 115 -120 psi in Drive. 1,2,3,4 and 5 shift are firm and at correct time. But the computer applies the TCS slowly which resulted in no apply when hot, untill I did the spring change. I know that the 3.0 application uses lighter springs in the TCC regulator valve and using lighter spring pressure should have caused slip in the 4.0 SOHC but instead the lock up improved? This is what I don't understand?

 

[PopRichie77]

Well, pulled the trans a few weeks ago, the 2 torque converter clutch related seals turned out to be good. I replaced them with new ones anyway and also the Torque Converter, also put the original springs back in the valve body. Had it back together on Friday but only drove for a couple miles, got to drive it over 50 miles today and the trans worked fine no flashing OD light. Will take more miles pulling the trailer to be sure it is fixed.