pcar928fan

I know EXACTLY what you are talking about... Oddly it is MY '84 that does this exact same thing too. I have changed tires on it (oh, wait, maybe it was the fronts that I changed), but I certainly DON'T think it is tires! I too thought it was the big pin that goes through the bottom of the shock because my race cars was loose once and behaved sort of like this but not quite. Mine seem fine too... I have not taken it in to the shop to get this issue figured out. Now I will wait and see what you come up with and try that with mine too.

I am thinking it is either a worn out hub, or hub bearings that are worn out on one side... Just a WAG on this, but it would be the first thing I would suggest to someone looking for this kind of trouble maker.

It is VERY annoying and unnatural. NOTHING like breaking the rear end on a 32V or even my 81 loose. This is something completely different. Not a corner balance thing either, that makes little difference in a 3300# street car on street tires with stock suspension. I don't think you can change perches on the OB and S cars anyway, so corner balancing becomes very difficult to do.

Lizard928

I am having this same issue with my 81,
It happened right before I went to the track I had swapped the springs to get it to a proper ride height.
I then had an appointment to go have one done, but then another fellow told me oh no just bring it around and we can set the toe. I reluctantly agreed. His method royally failed.

I made it home but he had put WAY too much toe front and rear.
I manually adjusted the toe. And it was ok for the track but I believe the issue is that the rear toe was not adjusted in line with the front, so the car is dog walking abit, and is excentuated by my larger tires on the rear.

I get a serious change between on gas and braking.
Just have to take it in and get an alignment done properly.

So my vote would be to confirm that the alignment lined up the rears to the frons when adjusting toe.

Landseer

I had a 944 that shifted lanes on acceleration, felt like it was something in the back that was loose --- was a bad steering u-joint.

Had loose rear on cornering the 928 --- lower front drivers's control arm bolts were coming undone + steering rack rod, drivers side, had fore-aft motion and needed a plastic bushing repair.

May be outliers, but for your consideration anyway...

SharkSkin

Putting the tires on backwards will eliminate them as a variable if it still does the same thing.

My suggestion about the drop link only applies if you're going to try to check for an imbalance, though if you didn't have to fight the drop link back into place then it's not impacting things. Good data point. You might find a scale at a garden supply, Moving & storage, or a recycle center or dump. The method I described is very crude, but I would think it would take a couple hundred pounds+ off-balance to give you the symptoms you describe, and if you can find a scale with even, level ground around it I believe you could see a gross difference like that.

All 928s can be corner balanced, though only the rear shocks are adjustable on early cars. If the car were sitting with too much weight on diagonally opposed wheels, it could still look fine, but behave as you describe. Additionally, I would expect the front end to dive sideways under braking. Also, to be far enough off to get the symptom you describe the car would have to be bent or there would be quite a bit of difference in spring perch adjustment when comparing the two perches on an axle.

The alignment is worth looking at. Get the wheels pointing straight ahead. Tape a piece of string to the back side of a rear tire at axle height, extend the string forward and tape it to the forward-facing tread on the front tire at axle height. Do the same for the other side. Now eyeball each side against the other. Anything stand out?

mark kibort

scot had put the washers on wrong, and had a ton of slop in that area. it made the wheel wobble under race conditions coming into a turn at 120mph!
we got a new washer and buttoned it back up. Not much of a problem under acceleration though. You could tell something was wrong on the lift, when you move the wheel around, and man it moved!

jack it up and lift up the wheel with a tire iron on the lug nut. if you can lift it up easily, the upper control arm is bad, or you can sometimes detect shock failure. the lower, you can test by moving the wheel around, or trying to move it around with it in the air.

The only time ive experienced this phenom, was when i bolted on two different sized tires. gas it, and it would pull badly.

mk

Mrmerlin

Dave thanks for the extra info I will be doing some testing today
Mark thanks for your thoughts, I did remove the right lower link pin (lower shock mount pin)to check for weird assembly but like I said all the parts are there and correctly installed, the rear end is tight the bearings are tight,

I did find that both of the upper control arms were reinstalled with out the benefit if the safety washer bing installed ( on the forward facing outer connection to the hub carrier)so I fixed that ( the rear crossmember was removed prior to my ownership and i guess they forgot how it went back together) The flat washers on the front side of the outer upper control arms were both on the rear sides of the bolts so if they decided to slide off ( the upper control arms)the pivot point they could and the passenger side was moving forward on the outer post. The upper control arm doesnt have much to do with front to back motions just in and out positioning???

SharkSkin

No, under load there is torsion against the hub carrier as the wheel/axle pushes forward against the bearing. The lower pivot pin takes up some of this torsion, but it all flexes under load. This could be a factor in what you're seeing.

Mrmerlin

Well I think I have found the culprit, without doing anything other than torquing the suspension points the pull seems to have gone away,
I think a new set of tires and wheels would also be a good idea.

Anyway the the bolts that required the most tightening were the 2 eccentric bolts that hold the inner portion of the lower control arms to the rear aluminum crossmember, the correct torque is 146ft/lb ( they were both tight with the wrench) however with the torque wrench on these bolts they turned a lot to make them tight) the front connection to the chassis is 104 ft/lb this one is not really able to be done as the socket wont fit into the small opening in the chassis and then the lower shock/link pin is 88ft/lb.


I also fixed the alternator charge problem by fitting a new regulator and soldering the ends of the ground wires engine to block and the end on the ground strap. I also took the alternator apart from a hint from Garth, I am glad i did as it was filled with rocks and debris. Now the charge is 14.2 at idle and with the lights on it goes to 13.6 at idle. I think all is good now. I will do some more testing with the tire pressures.

Leon Speed

Sweet! Another mistery solved.

Note to self: check rear suspension torque when replacing shocks.

jon928se

[QUOTE=Mrmerlin;5949041]Well I think I have found the culprit, without doing anything other than torquing the suspension points the pull seems to have gone away,
I think a new set of tires and wheels would also be a good idea.

Anyway the the bolts that required the most tightening were the 2 eccentric bolts that hold the inner portion of the lower control arms to the rear aluminum crossmember, the correct torque is 146ft/lb ( they were both tight with the wrench) however with the torque wrench on these bolts they turned a lot to make them tight) the front connection to the chassis is 104 ft/lb this one is not really able to be done as the socket wont fit into the small opening in the chassis and then the lower shock/link pin is 88ft/lb.
QUOTE]


Merlin

on my 88SE I discovered the camber and toe eccentrics weren't torqued to spec resulting in a random clunk. As this was winter I never managed to provoke strange handling - driving too carefully around the city.

I just tightened the toe eccentrics as tight as the camber eccentrics felt - as you state you can't get a socket anywhere near them.

Mrmerlin

for anyone looking at their rear end there are 2 eccentric connections one for TOE on the front of the control arm and one for TRACK where the control arm is connected to aluminum crossmember torque is 146 ft/lb at the crossmember and 104ft/lb the front connection and 88 ft/lb at the lower link pin

hacker-pschorr

Same thing with my wife's VW. There was a strang --clunk-- when launching and taking a slight turn.
I found a front lower control arm bolt loose.