General Maintenance & Repairs - Driveshaft vibration

Got an 01 Trans Am M6 with the stock driveshaft. I was working under my car and decided to look at the driveshaft. With the tires chalked at the rear and the front and ramps (tires unable to turn or move) i could grab the driveshaft at the front and twist it about 1/2 an inch to an inch. I thougth there was supposed to be 0 play in the driveshaft. I have a vibration at 45 mph and around 70 and I be this is causing this. What do you all think? How should it be fixed, do I need a new driveshaft? Anything else I should buy if I need that? Thanks!

You are experiencing gear slack in the trans and rear. That is normal. If you are experiencing excessive vibration at speed your shaft *might* need to be balanced or your tires need balancing.

tires are balanced. Yes I am getting a vib at speed at 45 mph and 70 mph. Think this is driveshaft related? I thougth there was supposed to be no play in it at all?

There is typically plenty of play in the trans, but really shouldn't be at the rear e.g. .007".

Is the vibrations between 45 & 70 or at those two different specific speeds?

happens at two different speeds, specifically those speeds I feel a thumping/vibrating underneath the car under my seat towards the rear.

Ah, that might be the output shaft bushing of the transmission.

thanks, whats the best way to check? My tranny mount is cracked so I'm replacing that this weekend. Do you think a torque arm bushing could cause this? I don't see how the tranny mount could cause so much thumping at those speeds. The thumping is mainly throughout 4th gear.

Not the tranny mount. The output shaft bushing. It's the bushing the driveshaft slides into the back of the trans. Start with the mount if it's cracked, but then remove the driveshaft and inspect the bushing.

Very interesting, I am getting the same exact vibration in my car.

However, I have had my tranny rebuilt by D&D Performance about 40k miles ago.
Since then I have replaced the tranny mount bushing.

Let me know if your output shaft bushing is the culprit.

You might also look for stuff like strange tire wear
or bulging, driveshafts don't usually go out of
balance unless you lose a weight and that should
be obvious by inspection.