gdwprice

Hi everyone. I'm still pretty new and learning. I have an '88 3.2 with 103,000 miles. It's displaying a vagueness that has me concerned. Under acceleration the car pulls to the right. Lifting off the accelerator the car wants to go back to the left. This only happens under acceleration and lift off. Gradual acceleration, coasting or braking the car runs straight and true. It's only under hard acceleration and then lift off I get the right pull and then left return. It's noticeable and unnerving.

I recently put on new rear KUHMO tires - replacing the KUHMO tires that were on the car that wouldn't pass inspection. They're standard sizes. I understood the car would squirm a bit on new rubber but I've put 600 miles on them already and it's no better. I'm not sure the tires are responsible but it was immediately after I fitted them I noticed the car felt like it was floating. It was so bad that I had to pull over to check a wheel wasn't loose! Prior to the tires the only thing I noticed was that the car felt vague at the back when I lifted off the power at 90ish and would gather it's composure if I put the power back down. I've had a look underneath and see nothing loose or any play. Any advice would be appreciated.

theiceman

i was thinking tires before I read your second paragraph .

Find a buddy with a 911 and see if you can swap wheels for a test .

I have a whole spare set of wheels for my car .. maybe you can find a lister near you wit the same situation.

whalebird

lots of places to look for a problem here. My first stab is the rear control arm bushings and spring plate bushings, however it could simply be an alignment issue. Also, front chassis components can create strange feedback as well. I think my "safe" advice is to plan on having all of the suspension looked at for wear, including the rear swaybar mounts which are known problems. The reason I suggest a blanket upgrade to the bushings/shocks/tie rods etc. is that these cars are pretty old by now and need these components if they have not already been addressed. Most of the gurus here may agree with me, but I have been called out for suggesting overall, or system-wide repairs on these older cars. Again these cars are getting old, these sort of chassis problems have an element of safety attached, thus my "safe" advice.
Stay tuned, you will get a lot of info from our fellow Rlisters.
congrats on that pretty coupe. If you have any service history, modifications, or known repairs, share them as this may help identify the problems.

gdwprice

Thanks for the advice. I wondered if the tires are exaggerating the problem but it was preexisting. I have had a few BMW flat twins over the years and they had a habit of pulling to one side under acceleration. It's been so many years since I rode one I can't remember if it was to the right or left. The engine was mounted in the opposite direction in those.

I had a theory that maybe the rear right shock was giving more under acceleration causing the pull to the right and then letting off the power it would return faster (perhaps due to less fluid) causing the return to the left? The car has quite an extensive history - new rear axles, top end rebuild in 2001 with new guides and valves (3 angle seats), new clutch at the same time etc. It has every receipt going back to the window sticker accounting for over $20,000. It had a new m/c and front calipers as well as new ss brake lines; this was due to water in the system and the owner having two new knees and being unable to pump the clutch in traffic so it sat for 2 years. The tires that were on the car were nearly 10 years old and worn evenly so I was pretty confident in the alignment. As far as I'm aware the shocks are original. There's no evidence of leaking but I can find no receipts for replacement so assume them to have covered 103,000 miles. They also have the same (cosomoline?) on them that appears throughout the underside.

Although I can not recall the symptoms before the tires I was aware that lifting off the power at higher speed causes the back end to float, for lack of a better word. I wondered if that might be due to the lift from not having a tail on it. Now I'm not so sure.

I need to get back under it and double check but I'm busy expecting my first child - building cribs etc. I took it out for a 500 mile blast on Saturday (400 in heavy rain) as I suspect my alone time faces a severe impact in the coming months!

Auto_Werks 3.6

If the problem started with new tires, I would start at squre 1; double check the tire pressures. Try 32psi front and 34psi rear (cold). Sorry if you've already BTDT

gdwprice

BTDT? I have the pressures at factory which I think is 29 front 36 rear? Whatever the sticker under the hood says. Does anyone know the life expectancy of rear shocks? I guess I was hoping someone might have experienced a similar issue and been able to advise on the most likely problem. It definitely started with the tires. The old ones had almost nothing left on them and the car was rock solid. There's so much tread on these and it's pliable by hand. I just don't understand the desire to pull right unless the torque of the engine is being transferred in a fashion to push the car more to the right.

I do have a slight leak around the transmission where it seals to the axle on the drivers side. I's a LSD but it's not dripping - just damp.

UberXY

Your spec tire pressures were authored in 1988, and they were reasonably accurate for 1980's tires. It's now 22 years later, and tires have come a long long long way. I would start experimenting with tire pressures if I were you, in some simple systematic way. Take an air bottle and a good gauge, and find a lightly traveled stretch of road where you can reliably induce the problem, and start making alterations. Better still at a track day.

rusnak

My standard advice is to push sideways against the rear bumper with your shin, while looking at the wheel rim for wobble/ play. Sometimes the rear wheel bearings go out, or the wheel hub nut can come loose.

Congratulations on the bambino!

ivangene

get it in the air and have a push/pull party... push and pull on everything you see conected to the wheels front and rear.... listen and feel for clunks and slop and play and noise and and and .....

BTW Welcome

BTDT = been there done that

gdwprice

Thanks. My wife's 37 weeks so I gather it's anyday now.

I did do this just after I fitted them and the movement seems to be flex in the tire wall! A friend suggested they'd get better with use but I have at least 600, maybe 700 miles on them. I think I'll play with the pressures as suggested above and see if I can reduce the effects. I won't be driving the car on the salty roads over winter but if I can't find any other issues I'll put some better tyres on it come spring. A friend runs Kuhmo's on his M3 without any problems but it's obviously a much newer car with less tire profile.

gdwprice

LOL - initially I thought you meant 'get it in the air' through irresponsible driving. I only do that in my wife's car. . . .

I did as you've suggested but I think a second more thorough inspection is in order this weekend.

There is a slight creak if I push the car hard up and down on the rear bumper but it settles the moment I let go.

ron mcatee

That noise is probably the rubber bushings on the spring plate(s). After that many years, they begin to sound off.

Bob Rouleau

Start with the simple things first. Swap the tires side to side. If it pulled left under power and right when coasting and now it does the reverse, the problem is a tire. If one tire is a bit larger in diameter (or, overinflated compared to the other side) a 911 will exhibit the behavior.

If nothing changes when you swap, check alignment, the thrust angle is suspect, i.e both rear tires need to be pointed in the same direction. One rear wheels may have toe in and the other toe out which would also cause all sorts of handling issues. Since you had handling issues before, this is likely the problem and while on the alignment rack, check for worn bushings and joints.

Best,

Auto_Werks 3.6

Try to bring the rears down to 33psi cold. You will be surprised at how much difference 3psi makes on these cars.

For what it's worth, I think you have some other issues going on as well. You have gotten some good advice from everyone else. It's time to start looking for broken parts. Bad new tires can reduce overall grip but they shouldn't cause with problem you identified. A worn out bushing or wheel bearing etc etc will.

I'm not surprised you see some tire wall flex, and I doubt highly that your tires are going to get any better with age.

I would also check the rear sway bar links and body mounts. The mounts are prone to break off the body tub, and if you lost one it might do some weird things as the suspension articulates with the throttle. The mounts will be fairly obvious when you look underneath, pull down on the bar and see if it moves away from the car.

Good luck with the investigations.

jwasbury

Like Whalebird, my first thought ran to suspension bushings. Maybe because I just went through a full refresh/upgrade on my '79. The original rubber bushings were TOAST.



That's the inner springplate bushing...totally hosed. You can visually see if those spring plate bushings are bad by looking at the torsion bar covers just in front of each rear wheel.



The photo above shows the area I'm talking about. The torsion bar covers at the end of the springplates should be centered if the bushings are good. With my worn out bushings, the sag was obvious.