88 Carrera front thump noise

[Raulg]

88 Carrera with 80k miles. Occasionally driven. When backing it up and turning the steering wheel to the left i hear a loud thump. It appears to be coming from the front passenger side. I feel the thump in the car although I cannot detect movement on the steering wheel. There is no vibration during regular driving. I jacked the car up and tried to find any play on the front passenger side wheel but seems tight. A few months ago I noticed this side (front pass) of the car lower and adjusted the torsion bar bolt and it leveled the front.

Could this be a bad torsion bar? (or bushings? If so, how could I check it? and replace it? If that is the case, should both front torsion bars be replaced? Is there an upgrade to the stock torsion bars?

When I back the car up with the wheels straight there is no noise at all.
Please help.
Thank you - R.G.

[Flat Six]

Sounds like it might be RF sway bar mount/bushing or tie rod end. Might not notice handling change if driven occasionally / not aggressively.

[gtc]

I doubt your a-arm bushings are shot yet.
My wild @$$ guess would be that you have boge shocks with a loose strut insert, or perhaps a worn ball joint or tie rod end. But I suspect you would have noticed those when checking the wheel bearing.

[Flieger]

My guess would be the sway bar. My Welmeisters (through-body) have lateral play and make a snap/clunk only once, when I back out of the garage or turn the wheel significantly for the first time.

[Raulg]

Thank you all for sharing your knowledge. I will be checking the sway bar mount/bushing, tie rod end and shock this weekend and post any findings. Thank you. R.G.

[Raulg]

I placed the car on jack stands and removed the metal cover under the steering rack. Cannot find anything loose.
I read another thread about this problem and someone explained that this is due to the front wheels pushing against each other in near full lock conditions, I think it is call Ackerman steering condition or something like that. In which the pushing causes the wheels to jolt at full lock or near full lock.
I just don' recall my car experiencing this condition a year ago and before. I don't think these cars would do that when new either.
So far no answers to this issue but the concern remains.
Any recommendations are welcome.
R.G.

[Flieger]

Ackermann is how the toe-in of the wheels must change as more and more steering lock is wound on. If you look at the car from above, the inside wheels must travel on a smaller circle than the outside ones. If the car is not oversteering, then the car velocity is always tangent to the circles made by the rear wheels, which both lie on the same radius line. The front wheels are in front of the rear by the length of the wheelbase. The inside tire is closer to the center of the turn and this means a smaller radius. The smaller radius circle needs to turn more degrees to put the wheel even with the outside wheel or else you have differing wheelbases on each side. You have to turn the inside wheel into the turn more than the outside in order to get both lines from the front wheels to meet up with the rear line.

911s use the suspension kinematics to achieve this effect as the body rolls. At low speeds, the wheels are parallel so the inside one wants to plow wide and so the tire scrubs across the road.

Ackermann steering geometry - Wikipedia, the free encyclopedia