Johnny G Pipe

Hi folks, ongoing progress fixing up my 79 Euro has included a set of Gaz adjustable coilovers, which I have finally got dialled in - conclusion being that they suit being on the softer side on this car and my local roads. I have also replaced my steering arms and put in steel front lower ball joint units in place of the aluminum items.

The old shocks were toast and the car rides and handles much better now of course, however I am noticing over crests the car still feels like it is shimmying sideways on its suspension somewhat. There is also a little bit of a similar, slight but noticeable squirrelly feeling on hard braking at speed. I think it is more in the rear. I have a 356 and a couple of old 911s but this is the only 928 I have driven..its a relatively big old car, is this to be expected for a 40 year old, non-911, or is there a common fix for this?

Mrmerlin

This info is for the rear suspension,

For the suspension bushings in the rear I would suggest to replace,
the 4 dog bone bushings, 2 on each upper control arm.

Replace The big bushing at the eccentric on the LCA where it meets the rear sub frame cross member,
this will require the LCA to be removed from the car.
You need a big press for this one , you can see how much its moving by doing a road test,
full throttle in a lower gear then let off if the rear sways then the LCA is moving.
NOTE verify that the eccentric bolt is tight first, many are not properly torqued 140 ft/lbs

The bushings that go on the lower link pins could also be replaced, these are more difficult to replace and might not show an improvement .l

Note the two bushings I suggested will have the most impact on solidifying the rear.

The bushing at the front of the LCA is not normally replaced,
this is for the Weissach effect

Johnny G Pipe

Great, that makes sense, thank you.

Have I got these pieces right? (nice clear supension pic (presumed) courtesy of Ducman!) Also it seems for the dogbone its easier to replace the whole piece?

Mrmerlin

that is them ,

the dog bones take 3 mins to press in new bushings easy
the LCA is another story takes more time

Johnny G Pipe

Ok, two 28's and a 10 it is.

Thanks Stan.

KenRudd

Kudo's for the powder coated bits!

dr bob

FWIW, we NEVER paint race car suspension bits. Paint hides early evidence of stress failure and cracking. Just sayin'...

For your reported symptom of apparent lateral movement, plan on replacing the mounting bushings for the steering rack. The original rubber bits have been living in leaked oil and power steering fluid for thirty to forty years. Our cherished 928 parts vendors offer replacement options in Delrin and aluminum. Delrin is more than sufficient for road cars and most race applications.

Also replace the tie rods and tie rod ends on both sides. Diagnosing wear on these can be very subjective. Unless they are way seriously worn it's not something you can easily see or feel with solo wheel-wiggling. If the car has more than 75k or so road miles on it, the steering will benefit noticeably from the new parts.

The front lower control arms are perhaps the most robust inner mountings of any on the car. The front bushing is molded-in-place with the mounting, bonded inside and out, while the rear sits clamped between a frame impression and the cover clamp. The front bushing will show cracking/splitting as it fails, allowing the mounting to move more easily. Once it starts to crack, movement in the suspension will continue to pull at and enlarge the failing faces. There are some urethane repair bushings/kits that purport to be better. Meanwhile, Mark at 928 International ships used control arms to the folks who made them originally. They come back cleaned and rebuilt with all new rubber in place, just as they were originally installed on the cars at the factory. Good for another 30+ years.

IIRC he has the same service for the lower rear arms as well as the front uppers.

KenRudd

Point Taken.

Johnny G Pipe

Thanks for the additional info Dr Bob.

Johnny G Pipe

Would anyone know the difference between p/n's for the dogbone bushing - I am getting 928 331 089 02 and 928 331 089 04, both listed sequentially in the parts PET for 78-82, but no clue as to which is which.

I presume -02 is earlier, but does anyone know if they are interchangeable?

Johnny G Pipe

Just to close the loop for now, 04 supercedes 02 and 01, as is the way of these things.
Just ordered the rear bushings from Sonnen @ $40 each, not so bad. Off to eyeball my steering bushings now, I expect they are bad too.
Will report back when all fitted!

dr bob

Johnny --

The rack bushing "inspection" demands that you have your trusty assistant rock the steering wheel back and forth whilst you have a hand on the end of the rack housing with thumb on the crossmember in which it lives. By this time most 928's have soft or rotted rack mount bushings so the change in load as the steering is loaded will move the housing a little left and right. Car's that have sagged add some vertical movement due to the angle of the tie rods. Both plays, added to the wear in the tie rods and ends, offers steering that's indefinite at best, "floaty" as lateral and vertical loads change. The bushings themselves are swaged into the cast "ears" on the rack housing. They typically live clamped between the crossmember and the bottom shield, so are a little inconvenient to try and just eyeball for wear. For all the work to inspect you can almost as easily pop the old ones out and replace.