Transmission slips in second and drops randomly out of overdrive

BDEPEW

MEMBER
2002 CHEVROLET TRAILBLAZER
4.2L
6 CYL
4WD
AUTOMATIC
200,042 MILES

Okay, so I had someone rebuild my transmission (4l60e), then I blew a line and lost a bit of fluid and babied it to the nearest gas parts store (about seven miles). I had stuff to fix it on hand when it happened and some flex hose to repair the section of line. This is just a recent event I did not want to leave out in case it has any impact.

Now the transmission was doing this before that incident, it will drive fine for about forty to fifty miles cold and then it will randomly drop out of overdrive, I can drop it down into third with the selector and it will run fine. However when it drops overdrive I can let off the gas and the RPM will go all the way down as if I was in neutral. If I leave it in drive after letting the RPM drop like that it, when I accelerate it will not pick up the gear and will high rev about 4,000 (60 MPH), as if its in third gear. The floor gets hot when its about to kick it out of overdrive, and the fluid level is over of under filled. Any ideas?

Also, there seems to be some slippage in second gear, it seems like it slow to grab almost. After it gets it though it seems fine, now this happens even if it is cold or hot.

Any help or advice would be appreciated!

2 Replies

KENW1

MECHANIC
213 POSTS

Hello and thanks for visiting 2carpros. Com. This is a common problem with these transmissions and it's most often due to wear in the 2-4 band. When the band is worn and expansion takes place when hot the servo cannot go far enough to push the band tight on the drum. This will cause slippage and lack of engagement like you are experiencing.

The extra heat from the slipping can often damage the drum and require replacement of that as well. Since the transmission must come out and be disassembled to replace the band and drum I suggest a rebuild or replacement with a new or re-manufactured unit.