4L80E SLAMMING into TCC lockup. Help!

[vanvleet]

Hope you guys can help.....
I just bought a '99 GMC Savanna 3500 with a 5.7
When the tranny goes into lockup, it slams very hard. Feels like the rear end is gonna fall off. The tranny has been rebuilt 10,000 or so miles ago. Other than the lockup issue, It shifts great. Goes right into gear from "park" even when cold.
The tcc doesn't lockup harshly only when dead cold. After about 6 or so miles, it starts slamming into lockup. I can feel an ever-so-slight shudder when it comes OUT of lockup. Very light. Only noticeable if you're looking for it.
Also, the fluid level appears to be over full. Not sure if this would matter.
Any help on this would GREATLY be appreciated!

 

[ak diesel driver]

on our 6.5s the tcc won't lock until the engine temps reach 170*. I would also verify fluid level overfull is not good

 

[vanvleet]

Thanks AK.

 

[vanvleet]

*

 

[Ed HD]

On these transmissions, overfull isn't good. Suck enough fluid out so that it's at the top of the hashed marks when cold.

 

[Ed HD]

I meant when at operating temp.

 

[WarWagon]

High fluid level will foam the oil. Air compresses and causes 'issues' shifting, slipping, etc. You can loosen a trans cooler line and leak the fluid out. Sucking is the mess free way to do it...

 

[vanvleet]

Thanks guys!
Well, I drained the fluid down to normal level. No change in performance.
I called the guy who rebuilt the tranny today. He said he never changed the tcc solenoid and he thought that a faulty one might be causing the hard lockup.
Does this sound feasible to any of you?