Thom1

I have some vibration just over 65 mph. It seems to happen more under throttle. When you ease off the gas, the vibration lessens. The tires have been balanced on a Hunter machine,... new Hunter alignment, new tie rods, new wheel bearings, new front tires. The Porsche certified mechanic only had me to replace the tie rods before my alignment. He specializes in suspension work. The Hunter balancing machine did indicate some problems with the rims. He did say I needed new shocks and motor mounts. But, they were not serious problems.

Can some vibration be removed by replacing bushings? How difficult are the jobs? How much do the bushings cost? Do I need a new alignment after replacement? Are the upper and lower a frame bushings and sway bar bushings stand alone components to replace on the front end?

Erik - Denmark

Thom,
Did he lift the car in connection with the alignment procedure? - Ifyes, your from wheels has toe-out instead of toe-in and that can start such vibration. But then you also has wear on the inner side of the front wheels.
I have just been 'fighting' with my car for removing resonance/vibrations with high speed (over 200 km/h = 125 M/h) on German concrete roads with short wave roughness.
I changed the shocks all around to Boge Gas and the front upper A arms and the lower ball bearings and tha front springs (Braun for the Boge Gas) and the result were remarkable, but I I have still not tested the car in Germany (In Denmark we can loose the driving license when driving faster than 110 + 70% = 190 km/h and do not have many concrete roads)
It seams that the vibrations start due to a combination of play here and there - At least it feels like I got a new car after I did the above, and I have even not did the final alignment - This I will do Saturday
The rubber bushes in the upper A arms seam to be critical - Mine had longitudinal play and I cured this with a 4 mm thick poly-washer 25/60Ø - I got this specially made in a local machine shop.
Look at the upper A-arms, and you will see what I mean - The rear end are supported in both directions- Here I placed the poly-washer- By doing this I roved the longitudinal play and the A-arm is pushed forwards to the original position - Some people (Wally and Earl) claims that the Caster shall be adjusted to the minimum position, that is most properly due to this longitudinal play
Yes, for sure you need new alignment if/when you change some of the steering components. This you can do yourself - See the next number (#4) of the magazine 928 Forum - That's relatively easy to do the alignment, when you first have learnt it!

PorKen

Thom1 - have you checked the engine/transmission mounts?

Lift the engine/trans slightly and look for seperation. It's easier on a lift. I found that both my engine mounts are free floating, and the left trans mount is bad too.

When I 'get on it' with my bad mounts, I can really feel the vibes, man.

Weissach1982

Hello, My 1982 Weissach has a similar vibration, but it only comes on around 3000rpms. My 928 has been rebuilt recently and I have no clue where it is coming from. I have Koni adjustables all the way around if that is of any signifcance to the problem. Also this is off subject, but does anyone know what causes the ''clunk'' from Park to Reverse? Its a 3spd and I don't think its the transmission because it feels like it is near the front of the car. What would be some of these causes?

Chico Valdez

Hey,

I chased a vibration for a year. I asked my super 928 mechanic to replace motor mounts, trans mounts. I took the wheels off and had them straightened, rerounded (BBS RAs). And new Dunlops. Vibration gone. Mine was at 65mph and up to about 110.

DoubleNutz

Check your torque tube bearings they may be thrashed!

MikeN

What KIND of vibration.......through the steering wheel? Or for the whole car in general? Looks like you spent a lot of time on the front end of the car,........what about the rear wheels/tires. If the vibrations are coming thorugh the whole car at speed, but the steering wheel is stable, I would start looking at the back ones.

DoubleNutz

I will bet good money this is a torque tube problem and you guys are chasing all over the car for what I am 99% certain is his problem is. It's the tourque tube whipping because the bearings are either seriously worn or possibly gone.

MikeN

Pat -

You could be right.......but I would hate to change out a torque tube for $$$$ only to find out that I had an out of round rear tire, or a bent wheel, especially since it would only take a few dollars to find out.

jim912928

i get vibrations starting at around 60mph...had a 4 wheel alignment done a year ago...had the tires rebalanced...so it's not either of those. Looked at my motor mounts and they are flatter than a pancake! Sounds like you are feeling the vibration of the motor. By any chance is it hotter in the interior around the radio...shift linkage..cigarette lighter?....also a sign of motor mount failure as it will lower the motor and bring down the heat insulation thus more going in through the tunnel.

Easy check..crawl under and look at those mounts!

DoubleNutz

This is not a high dollar repair and you may not have to change the entire torque tube if the front bearing is toast (which it usually is) simply disconnect the front only and slip a new bearing in over the shaft and into the tube- heck the bearing are cheap... put in two. Sometimes the bearings do not disintigrate in the tube they walk back in the tube with time and the effect is the same...the annoying 3000RPM vibration (makes you wonder why Porsche did not put a stud or something in the tube and directly behind the bearing to keep it from walking back over time.

Take my word for it... if the mounts and suspension are fine then this is your likely vibration culprit and this was the simple cure for mine.

Erik - Denmark

Interesting and strange news!
What you said above sound to good (Too easy) to be true, but theoretically if the bearing is moving backwards that's possible that the trans shaft can start bending and make vibrations - I have never seen the torque tube disassembled, but I recall I have seen some sketch telling that the bearings is mounted in a plastic housing I.e. the outside and inside diameter of the bearings are smaller/bigger than the house/shaft -
Can you explain more about what you found and what you did? Do you remember what size of bearing you used?
Regards from Erik in Denmark