How do I know if my TC is locked up? When I tow (9k lbs) my rpms are higher then when I'm empty, leading me to believe that my TC is either not locked or it's slipping. empty, I'm 2100rpm at 70mph, same streach of road with load, 2400 rpm @ 70. Trans temps running about 220 loaded, 180 empty.

All stock except Banks TC, installed by previous owner.

 

Sounds like the transmission is slipping somewhere, good chance it's the TC. After reading your post some more I would say for the RPM's and temperatures the transmission is in 4th gear but not locking up. What rear gears do you have?

 

3.73. Would a valve body make a difference, i/e., provide more pressure to the TC?

 

Hmmm, Mine runs 1950 rpm at 70 mph no load. Stock tires and 3.73 gear.
I'm not sure, but I think the vb can only increase pressure within the tranny, not the TC.

 

If the TC is already slipping and who knows how long it was before the guy that sold it to you I would say no. The TC is already shot and only doing more damage to the rest of the transmission running it any longer.

It is possible the TC is not locking but highly unlikely.

Does the truck or transmission shutter at 70 MPH when you step on the throttle? If it does that's a good indicator the TC is slipping. If the rpm's go up and the speed only climbs slowly then it could be the TC is not locked or is slipping. Without being there to drive or ride in the truck is really hard to say.

My guess with the information given is the TC is toast. What does everyone else think?

 

No shutter at all, it really doesn't exhibit the symptoms of slippage, except that the rpms are higher than I feel they should be. When I accel, it gains speed while rpms rise. I just thought that if the TC is locked, towing rpms should be the same as cruising rpms.

Walt

 

They would be the same. You're either in a different gear, the torque converter isn't locking, or the torque converter is slipping. I don't believe it could be anything else.