dane

I'm a newbeee here and hopefully someone can give me some insight/advice.

02-GMC 1500 4x4 5.3 auto 33k miles. 4.10 gears with 315/75/16's

Only after the truck is warmed up....
Only when the trans shift lever is in 3rd (lever not in OD)....
And Only right before (1/2 - 1 second) before the trans shifts from 2nd to 3rd I feel a clunk...thud.

It feels like as if the TC is locking up right before the 2nd to 3rd shift harder than it should and thats what I'm feeling. I'm not even sure if the TC is supossed to lock up at this time / condition.

I took it to the stealership. I told them what I said above AND said I wasnt sure if its sliping and catching or what.

The Trans Tech test drove and logged the data as he drove. The data showed nothing abnormal. He says he didnt feel anything.

The service manager test drove and says he didnt feel anything.

I told them the trans has to be fully warmed up and for them to drive it around.... it was ok to do so.

Between the 2 test drives they only put 9.3 miles on my truck (averaged 4.5 miles per test drive) so I'm not convince they even had the trans fluid fully warmed up yet.

I went a head and had them change the trans fluid and filter.

Any one have any input at all? Any questions?

Any input is appreciated.

Thanks in advance
---dane