So right before I get on the highway my car had a strange vibration, I figured it was the road. As I got onto the highway it got worse, and something didn't feel right at all. At sixty miles an hour the vibration was terrible, and the faster I went the worse it got.

I pulled over (it was night and hard to see) but I took a peek underneath and nothing seemed amiss. No driveshaft hanging, no axles hanging, nothing weird. Checked the lug nuts, and visually inspected spacers (everything looked flush against the rotor). The vibration seems like it comes from the rear.

Any ideas to check guys?

My guess either a ujoint went or just something stuck in a wheel or tire. Take anything apart back there lately? Get the wheels off and start wiggling and looking.

Look for loose or missing bolts on the driveshaft.

Checked the lug nuts, and visually inspected spacers (everything looked flush against the rotor).

Any ideas to check guys?

Did you use a lug wrench to check nut tightness? And the second part of your sentence is unclear. What are these spacers that make things flush against the rotor?

Thanks for the quick replies guys, I'll check all this Monday morning when I get to work.

Zed Head, sorry the spacers are wheel spacers. I didn't have a lug wrench on me.

Look to see if you threw a wheel weight, Thats much more likely than a sudden drive train problem, shafts and axels usually make noises before developing the shakes.

Maybe steel belt, feel your tires for a lump.

My vote is for U-joint bolts being loose.

Maybe steel belt, feel your tires for a lump.

Another good place to look.

Thanks for the replies guys, so here is the update.

So I made it home and this morning I jacked up the rear of the car, and spun each rear wheel only to hear a slight clunk noise. Jacked up the other side, and same clunk noise. I took a peek underneath and saw my propeller shaft spinning, but it was off center. So I'm thinking my propeller shaft (transmission to differential) has gone bad. A little research online shows that you can't replace the u-joints in the Z's driveshaft. I don't have a lift available to me at the moment (two cars stuck on our lifts to get work finished up).

So does anyone know about if there's anything else I should look out for? Or do I just need to order a new propeller shaft?

Aha! Bad u-joint(s)! Good find. Don't give up hope. The reports of non-fixable u-joints are not all inclusive. Take your drive shaft to a good drive line shop and see what they say.

Ha ha, I went ahead and ordered a new aluminum one piece driveshaft. Might as well do it now then put in my RB and kill it later and with more damage. I don't know what else I should replace while I'm there though, shaft should be here Thursday

non-replacable u-joints.

What kind of z do you have?