Or which rear suspension bushings typically need to be replaced first?

 

Upper doglegs..

 

92833108902.

 

Unless the car has excessive negative camber, which can not be adjusted out (if you can't adjust the negative camber out of the car, you need the bushings above), Kinematic bushings in the front of the control arms are of paramount importance.

 

92833108500.

 

These bushings control the Weissach rear axle, which is essentially the precursor to the Kinematic, on the 993's.
The bushings allow a percentage of "rear steer" (toe changes) which is part of what makes 928's so fantastic to drive, when "fresh".
However, once these bushings get hard and take a set, all of this affect is lost.
Mechanical adjustment of the rear toe is almost futile, as it will change and stay changed until a large force is applied, whereupon the toe will be altered.

One of the most important bushings on the car, along with the front lower control arm bushings.

 

thanks guys.....
is urethane ok as a replacement?

and if so, does anyone know of a source?

(btw i replaced worn rubber front upper control arm bushings with urethane, medium "hardness"....i don't feel any vibration or harshness...in fact, i have much less. i agree with those who have said that worn front upper control arm bushings allow freedom of the control arm to yield easily and cause a jarring feel when they hit the end of the looseness from wear....my car tracks much better now...i'm not correcting the steering every half second and sweeping turns are no longer scary....i made my own so i don't know how they compare to powerflex but i used a urethane that's in the same "hardness" range that they use, and added a bunch of graphite to my lubricant to hopefully eliminate future squeaks....sadly i stil have a mild vibration at 85 to 88 mph.....i guess new shocks will be my next attempt to solve that problem)

 

Don't bother. Just get OE rubber.

The urethane doesn't last nearly as long in our cars. Trust me when I say you don't want to do this job twice any time soon.

 

I've heard about urethane breaking down.... I can't help but think that for that to happen, the actual mixing of the 2 parts wasn't adequate....but just guessing. i made my own front bushings from urethane and installed them last weekend. i doctored the mix and the lubricant as a test. the job wasn't horrible but my goal was to install something that i'll never have to touch again. i hope they don't crumble.

 

Also going to add the they dont like radial internal movement..and they tend to shear.

A lot of cars have bushings where they dont move, and aren't asked to take a 'twist'..they have a collar that move in or around them. Or they don't have an unusual load against them, like the dogbone bushings do, which is why their failure (loss of durometer) is so pronounced and visible. (you cant align rear camber anymore) compared to others.

Of course the ultimate fail to move away from OE, would be the shock mounts and front LCA's where you would need to re-engineer the whole front end around them.

 

so can the LCA bushings be replaced by a normal (relatively speaking) person like me or do i have to send them in to be redone? Does Greg do them?

 

Buy the rebuilt arms as the LCA bushings are cast on it.

 

Quick answer, no.

It's a bear.

 

are you guys talking about front or rear lower control arms? i haven't done anything to mine yet....but i probably need to get them spiffed up

 

Front, best to buy them whole.