Loud thump when I shift into drive or reverse

Take care of the Trac Off and Check Engine lights first. It could be a bad transmission or bad engine mounts causing the thump.

Does it shift really hard? Bad throttle position sensor can trip both lights and make the transmission shift at high rpms and shift hard even under light acceleration.

also would have the fluid changed and the filters cleaned on the gearbox as well as have the throttle position sensor checked regards js autos

there is a hairline crack in the transmission case...... Do u think it could b low on transmission fluid?

quite possably as the transmisission on autos are put under a lot of pressure if it is leaking under preasure would recomend a good second hand unit

Get a new car!!

The cracked transmission housing would have been some useful information when you first posted the problem.

You will need a new tranny because of crack. With new tranny you'll most likely solve both problems.

I have the same issue but no tranny cracks or leaks the motor clunks when put into gear I changed both motor mounts and the mechanic said the tranny mount is good is this normal for this year of car 2000 cavalier

Is it only when you are shifting from park to a gear or gear to hear or does it do it every time the transmission shifts?

I am having the same issue. Once in a while I will start the car, put in in reverse and it will thump into gear. Then, as I drive away it will thump with every gear shift. If I stop and turn off the engine, then restart it the transmission acts normal again and will continue to operate normal for several more days.

My daughter's car is doing this as well. But once they reset the trac off light, it stops doing it; therefore, it is not the transmission. I think it may have something to do with the brakes system as she needs new brakes as well.

Brakes won't cause Trac light to come on

Actuallt brakes can bexause the abs and tac sensor is right next to front brakes and it is all to common for these to get damaged there. It makes this nouse on my 04 ss sc monte carlo. It sounds like someone taps a metal bat against the bottom of car near the drive shaft. It onlt seems to happen when weight shifts like when u take from park ro reverse or reverse to drive i have little to no issues through other gears. I thought it was a loose drive shaft but my abs and trac control was disabled to so that seems to be theconstant here. Itcant be abs but trac control is my best guess. I do nor think its the tranny slipping but it could be gear related

The problem is a bad valve body. It can be changed without pulling the transmission. It will cause a bang when putting the automatic transmission in reverse or drive. Very loud bang.

I have a 04 2.2 cav it is doing same thing. When I disconnect the battery then reconnect it does fine for a few miles. It only happens when it gets put in gear and shifting into 2nd.

I had a similar experience with my 2000 Cavalier 2.2L (BASE) today. Temp guage stopped working (went from normal temp to zero), check engine and no traction lights turned on. A loud clunking sound came from the engine/trans whenever the automatic trans shifts when driving or simply changing the gear from drive to reverse (vise versa) Went to autozone, scanned the code and found out that my coolant tempreture sensor was unplugged. I plugged it back and all the lights turned off and shifting went back to normal and smooth. Hope this helps anyone who might have this issue.

I had a broken muffler hanger on my 2001 cavillers . When I would shift into drive or reverse the engine would rock a bit and cause the muffler or some part of the exaust to hit against the body . New hanger fixed the problem.