Crumpler

So as I was replacing front rotors I picked up on a potential issue.
With the tire off (passenger side) and my hand palming the rotor to move it back and forth I can feel a little (trying to choose my words carefully) pop or thunk -- as the wheel goes from forward to backward. It is pretty subtle and not audible, just tactile.

I had just replaced the rack and tie rods, so my first thought was " great" what failed now...

Further detective work and I can localize it to the upper control arm, more specifically at the more rear bushing on the a-arm, like some shift.



It does reproduce on the drivers side as well, so is this normal or am I looking at 30 year old bushings that need to be replaced?
I'm not looking forward to pulling them or paying for rebuilt a-arms...

What say my collective brethren?

FredR

You should not be able to feel any play. If you have the ball joint undone you should not be able to swing the arm up and down at all, at least not without a lot of effort. The rubber bushes can be replaced relatively easily. The ball joint is the bigger problem. The earlier models you can rebuild but the 87+ are not configured for DIY rebuild- urrrgh!

Getting the nuts undone proved difficult for me. On the passenger side you need to get the a/c compressor out of the way and on the driver side the alternatotor and the power steering pump. I thought I had some play on the passenger side ball joint so intended to pull the UCA. Getting the bolts undone with the car on axle stands and flat on my back was a bit too much for me so I abandoned that attempt. Undid the ball joint and could not feel any play in the ball joint or bushings so boxed it back up. Will defer until next year -hopefully with a better lever on the socket.

dr bob

Following on Fred's description, the original bushings are bonded to both the shaft and the arm. If you can feel play in either bushing, it's fractured or come loose, so deserves replacement. The nuts in the engine bay can be a BIT of a CHore to access, and are pretty darn tight when installed correctly. Easier from below than above, much easier as part of a MM project while the crossmember is out of the way. Otherwise, it's long wrenches and short motion, or as Fred suggests "just" drop the lower engine accessories.

When checking balljoints for play, in my experience it's best done with a dial indicator, a clamp and a pry bar. The ball in the upper balljoint is held together by the stud and tension on the nut, sort of. The joint sees minimal vertical loading, so testing for vertical wear will almost always show little or no play. Instead, this joint sees radial loading as you go around corners and use the brakes. That's the movement you are looking to test with the dial indicator and the bar and clamp.

Obviously this can't be tested once the balljoint is separated from the upright, as by then the ball can pivot and no way to get an objective measurement.

It would be way cool to have the ability to force grease through the upper balljoints. A Zerk fitting on the back is a first step. But the ball needs to be completely unloaded (read: nut removed, separated from the upright, boot removed, and ball pushed up into the housing) before pushing in any new grease. This requirement, plus risk of contamination, points to why we don't see Zerks on these parts any more. Oh, and "lifetime" lubrication -- with a predictable lifetime.

FredR

Bob,

I figured that if there was anything wrong with the upper arm I should be able to feel it whilst trying to push the wheel in the 12/6 and 3/9 axes [spelling?]. Could not feel anything at all. I also tried to feel any movement on the ball joint stud itself and again could feel nothing but like you say that is not a conclusive test unless of course it is totally shot and then there is no debate.

Interesting comment about the stock bushes being bonded - never come across that before. I know that replacement bushes are a press fit but of course that does not mean it is something Porsche would approve but I was a bit surprised to learn of that. That being said presumably Porsche would set them such that they are in the mid travel position.

For the lower arm given they are the same part number both sides I figured they must be set such that the front mount axis is at 90 degrees to the centreline of the suspension arm. Then the arm can move with the flexure of the rubber. This made me wonder what happens if one runs with a lower ride height.

Rgds

Fred

Crumpler

Appreciate the feedback gentlemen.

I don't have instability in upper ball joint AFAIK, but I also wasn't aware that I should check for it at load. I will look at that.

I had done a quick search for bushings last night and saw that the vendors offer kits. Then I saw directions that involved a pretty large industrial press being used, and I started to back pedal a little -- since I don't have one . Can you pull it off without a large press?
I'm upto the task off taking the arms off.

dr bob

Doesn't need to be checked "at load", but can't really be checked for radial wear if it isn't installed. It would not surprise me to find that the preload on the ball is maintained by a spring in the top. If so, a little pressure with a clamp might make enough room to add grease around the ball from the bottom with a needle injector.

I'm a little more concerned about the bushings. They deteriorate with age, vs the balljoint that only wears with use.

The replacement bushings I've seen are a workaround to the original fitment method, with an outer sleeve that's bonded to the rubber. So a press fit of the sleeve means the rubber moves with the arm still. My statement of the bushing bonded to the control shaft should read that the rubber is bonded to a sleeve, and the sleeve is clamped on the shaft axially by the nuts at the ends of the shaft.

On the lower arm bushings: The car is indeed intended to ride with the lower control arms horizontal. Is a car lowered 20-30mm going to damage the bushings? Hard to say. The car obviously has that position within its available suspension travel. I'm not as worried about the static position at rest, but the idea that one might be extending the normal travel range in compression. It will hit bump stops (or the road) more readily, but how that affects the life of the rubber is tough to answer.

----

I watched a Science Channel "How They Do It" episode about something, where they heat urethane strips and pack a mold cavity to make a vibration damper for their product. It would seem that one could do the same for the LCA bushings, as it was done at the factory. Get everything scrupulously clean, heat it up, then pour in the right durometer stuff to form a new bushing in place.

Or just buy a rebuilt set from Mark @ 928 International. More likely this for me

FredR

You wil need a press whether the thing would be classed as large depends on the size of the things you have seen. I would say a relatively small press is adequate as I have seen some pretty big ones!

I would think something ike the Harbour Freight 12 tonne shop press would be perfect for the job but how often do you really need such?

I have a squeak when travelling over speed bumps that I am trying to identify and ultimately eliminate. I had a suspect lower A arm and have just replaced that but I fear the root cause is tired UCA rubber bushes. One way or the other I should know in the next few days when I finish my current work programme.

Taguid

I replaced mine with rebuilt UCAs but I pulled the engine for a second time to do it. It was just easier to get the required 103 ft lbs of torque with the engine out. Be sure to use new nuts when reinstalling to get proper torque.

Crumpler

Thanks Bob, the smarter move would probably be to buy a refinished set and have done with it. It's hard to resist the DIY siren song, however... We'll see, this is several projects down in the que.

Fred, good point my friend, how are things in your part of the world? I'm encouraged if a HF set up will do the trick -- I will put it next to the HF pipe bender that I also used one time...

Tracy, that is a nice rig, they say only real men pull the engine -- nice work.

supercedar

I just replaced upper and lower control arms on a 88 and did not remove any accessories. I have lots of scratches on arms to prove it though.

FredR

I struggle to imagine how you managed to remove the UCA's without demounting the accessories. Simple enough to drop the alternator and move the PS pump to one side, same for the a/c compressor. Mine were removed or displaced for other reasons but at least I could get a socket and a good lever arm on the nuts.

Ducman82

i have done it before with engine in and not removing anything..... but WOW, what a PITA... lol

dr bob

Fred (and Dave & Jake):

I was mentally re-doing this work in sympathy, and remember that I have a set of extra-long combination wrenches, box on one end open on the other, that may have played a part the last time we did a clinic car suspension. One of the UCA bolts does the duty holding that angle bracket/support for the cross-member on each side. No option to move that out of the way though.

[scratches head where hair used to grow...] I think if removing the UCA bolts was a good experience, I'd work harder at remembering it.

FredR

Bob,

I was trying to find a removal method wthout removing that bracket- perhaps that was where I was going adrift. For some reason the decaying grey matter in my cranium was under the impression that bracket could not be removed without dropping the cross member - durrgh! I'll take a look at that later today if and when I can get my tired old bones under the thing- currently running on one cup of coffee but the nut has to be removed with that bracket captive surely?

Those who have done this without removing anything should apply to join the Fantastic Four. Why they did not design this to remove the fastener from the outboard side is beyond me much as I appreciate the need to stabilise the position of the arm.

Removing them has currently been relegated to next year's project list! Much easier if attempted on a lift [I suspect].

Rgds

Fred

supercedar

Drivers side was the toughest! I did remove the oil filter.
The arm damage was due to front upper nut. I didn't realize what I was doing till I pulled it out.