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4r100 torque converter lockup?

rockdog57

rockdog57

Ghetto fab garage owner
Joined
May 21, 2020
Member Number
868
Messages
609
Loc
Lindon, Utah
The 4r100 in my 01 f350 7.3 torque converter locks then unlocks when I get over 40 to 45. A little history…the trans was rebuilt about 70,000 miles ago by John Wood from Southern California. He was the go to guy at the time. He built it with extra discs, his own valve body, billet converter yada yada. Obviously I’m not knowledgeable about automatic tran’s. I’ve surfed the net and came up with a little bit on what commands the pcm to make the lockup. Accelerator position is one. I’ve had to put one in it in the past. So I ordered one to throw at it. The pcm just grounds the wire to get it to lock. But beyond that I just don’t know where to go from there. I have AE for the truck but don’t know much beyond pulling codes with it. Not a tech so any input would be appreciated.
 
Brake pedal signal is a big one in the OBS trucks with E4OD, different trucks but similar, but something worth looking at.

Also at one time I had a partially broken wire in the harness near the diff speed sensor causing a couple issues, torque convertor lock-up/unlock being one of the issues. Does your speedo ever do anything strange, bounce/drop out, etc?
 
Brake signal is a big deal like mentioned. Swapping to LEDs creates problems. Bad brake light bulbs. Including third brake light, but yours seems rather specific.

VSS is a good one to watch, as well as your TPS.

Do you have anything like a chip, or banks trans command?

I have a gear vendor and the GV electronics failed causing a similar problem that was very difficult to find.
 
I put a new speed sensor on the rear diff a few months ago. The speedo will stay on zero for about half a block on first run of the day. Then it pops up to speed and works fine after that. That’s why I put the new sensor on. It didn’t cure it but it wasn’t doing the lock unlock deal then. Brake lights all work and are stock. Truck is always hooked to a trailer but that has never made a difference in the past. New pedal gets here today so I’ll give that a shot first.
 
Check the brake interlock solenoid for the shifter. Speedo power runs thru it and it can cause shifting issues.
 
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