Half shafts

how can you tell if you need the half shafts replaced? My Grand Am has 112,000 miles and it has just started making a thumping noise up front. It seems to match the rotation of the tires pretty well and changes pitch when turning. How much to replace these?

Don't assume it's the half shafts. What you're explaining will also come from a busted motor mount. Take it to a shop and ask them to check the CV-shafts and the motor mounts.

Then inner CV joints will make a thump when letting off the gas when they go bad. The outer CV joints will start clicking when turning the car when they go bad.

Get under the car and check the CV boots to make sure they aren't torn or ripped. If the boots aren't ripped it won't take long to contaminate the bearings and start losing all the packing grease.

As the previous poster mentioned it could be a bad motor mount. The rubber will break down over time. You can check these yourself too.

You didn't mention the year/engine type of you GA. Mine has 3 motor mounts (all which are bad) and it shakes like crazy when idling at a stop light.

If you plan on doing any type of work on your car I'd suggest getting a haynes/chiltons manual.

thouhgt I would keep you informed of progress. 2 shops have looked and both conclude a bad transmission. A bearing in the differential? WHen going straight there is a constant repetitive bump. slight turn to the right and the noise goes away. Teh mechanics say it is due to pressure on the bearing going straight or turning left. Right turn relieves pressure. Not sure I want to invest in a rebuilt transmission at about $1200 plus install of about $600.

Advice?