[777funk]

My E4OD rebuild has about 10k miles on it. Last night I was heading down the road when I heard a clunk then high revving without power. After the van ran out of momentum it wouldn't go no matter what gear. What could my problem be?

 

[Mark Kovalsky]

It's something mechanical that broke inside the trans, or it is a broken flex plate.

 

[777funk]

This happened almost immediately after I locked the torque converter clutch (switched TCC lockup mod) if that gives any clues.

 

[Mark Kovalsky]

No, it doesn't.

 

[777funk]

Just took off the inspection / bolt-up cover for the flexplate/torque converter and the flywheel and torque converter are both spinning with the engine.

If I engage the TCC lockup clutch, I get a zinging/whizzing sound that I never got before. Could that mean I have a torque converter or maybe fluid pressure problem?

EDIT: I should add that since this was rebuilt, there were times it would take a second of idling in gear for the pressure to build and allow for it to move. Could I have a bad TC drain back valve?

 

[Mark Kovalsky]

You could have a bad drainback valve. That won't cause this problem. You have eliminated the flex plate as the cause. Something broke inside the torque converter or the transmission. A removal and teardown is the only way to know what broke.

 

[777funk]

I checked line pressure last night and had 190-200 psi in all ranges. It'd dip to 30-50ish for a split second as I ran through the gear selector then pop right back up to max line pressure. Not sure what this means.

 

[Mark Kovalsky]

It means something broke inside the torque converter or the transmission. A removal and teardown is the only way to know what broke.

 

[777funk]

Would the Torque Converter Clutch lock without fluid in the torque converter? I assume not but don't know. I'm going to see if I can drain the TC (if it has a draincock) as a check for fluid presence.

If the TC's fluid system was not working, would the TCC locking (in 1st gear) allow movement?

 

[Mark Kovalsky]

The torque converter should not lock when the truck isn't moving. If there isn't fluid in the torque converter the torque converter cannot transmit any torque to the input shaft, and the truck won't move. The torque converter clutch can't lock without pressure, and if there is no fluid there is no pressure.