U-joints?
 

I recently purchased a high-mile FD. I think the u-joints
are bad, but it could be something else. I have a lot of
drivetrain noise like clunking. I also get a pretty bad lurching
when pressing on or stepping off the throttle.

Does this sound like u-joints? Or a clutch going? It's certainly
possible that it may be several things all going bad, such
as u-joints, ring and pinion, etc.

I've seen that the mazda u-joints are not serviceable.
Has anyone used the mazdatrix "aftermarket" driveshaft
that has serviceable u-joints?

BTW, the chassis has 119,000 miles on it and I wouldn't
be surprised if the rear had never been serviced.

Thanks for the help.

Well it sounds as if you have some previous mechanical experience on other RWD cars.. Typically u-joints and ring and pinion slap are not the culprit of rear-end looseness on a 3rd gen RX-7.

The first thing you should do is immediately replace all of the 6 pillow-ball bearings present in the lower control arms and outside joint of the upper control arms. After that I would suggest differential mounting point bushings and then moving on to engine mounts if things have not improved.

Also, get under the rear of the car and examine the long black steel structure connecting the transmission housing to the differential. Look for any signs of cracking, bending, broken mounting points, etc.

Heh, yeah I came over from the mustang world (uh should
I have said that?).

Rear suspension bearings are a thought from what I've
read (and suggestion of my brother who's had an FD for
a couple years). Upon searching though, it seems that
most people who complained of 'clunking' noises while
turning fixed it by replacing those bearings. I haven't
experienced any alarming noises while turning, mostly just
pressing/releasing the throttle.

These bearings are definitely already in the replacement
pipeline though simply due to the car's mileage.

The 120,000 mile old R1 suspension doesn't bother me
nearly as much as the lurching at on/off throttle. Makes
for an annoying ride.

I'll definitely be crawling around and looking at the ppf
and everything I can once I figure out how to get this car
in the air.

Thanks.

When I first got my car some "mechanic" left the four bolts on the back end of the driveshaft loose. When I finally figured that out, one was gone, one had lost the nut, and the others were about to. Luckly, no damage. It clunked nicely, BTW!