Torque converter clutch slipping?

GetMore · April 10, 2006

I recently noticed some slippage in my transmission. I think it is the clutch in the torque converter. I think (just don't remember now) that I put it in T/H mode to lock the clutch in third gear and it still acted the same, which is why I suspect the clutch.

It is an intermittent problem, seems more likely to happen when the transmission warms up.

I had the transmission flushed and it did not seem to make an improvement.

According to my brother (he recently took a transmission course/seminar) the TCC solenoid in the truck is either on or off, and works or doesn't, so I should not be dealing with any kind of partial failure of the TCC solenoid.

The check engine light does is not illuminated, though I have not checked it for any codes. As far as I have been told I should get a CEL if the truck detects slippage.

I wouldn't be terribly concerned, except for the fact that the transmission temp will approach 200 degrees sometimes.

As for the symptoms, it is not always easy to notice. The slippage is 200-300 rpm, and light/moderate changes to the throttle will typically produce a maximum of 100 rpm variation.

In other words, when it should be reading 2000 rpm, sometimes it will be at 2200, and applying more throttle will cause it to go to 2300, even before the truck accelerates. Letting off, but not all the way (IOW keeping the TCC locked) will allow the revs to drop to 2000. Sometimes it will stay at 2000 when I give it gas again, even at moderate throttle, sometimes it will go back up to 2200, even at light throttle.

The truck recently turned 90,000 miles, it is a 2001 2500HD, 6.0/4L80E all stock except for the computer tune, and it was doing this on the stock tune as well.

FWIW I have towed 5000-6000 lbs of trailer a number of times and I hadn't noticed anything different.

Anyone have any suggestions?

TIA!