993Porsche

After searching the forums I didn't find the solution for this problem. Although I changed the motor mounts, the vibration is still there and is felt in the seat or the interior body when the car is accelerating over 50 mph. My car is a C4, has over 138K miles, with stock springs and shocks. Has anyone ever had this kind of problem before?




Thanks,


Ken

melman911

CV joints?

Marlon

Ken - when was the last time you had a good high speed spin balance? You also could have a bad tire and / or rim. Some folks have suggested high pressure water spray out of your brake rotor cooling holes. Do you feel it in the steering wheel at all, or the car 'body' only?

AOW162435

Torque tube / center drive shaft bearing wear?


Andreas

95 C4 993

time to replace those shocks and springs?

black ice

What about play in rod ends? Someone with more experience might be able to say if this is common cause of intermittent wobble (toe change).

993Porsche

The shop that I use spin balanced the front wheels on the car and spin balanced the back wheels off the car. The fronts are ok, but they told me that the back wheels were bent. They couldn't repair them, so I took them to a specialist that repairs wheels only. So I'm pretty sure they are Ok. But I didn't high-pressure water spray the rotors though. I'll try that later today or tommorrow. And yes, I do feel vibration in the steering wheel when I accelerate. Glad you asked that question.

This is also a possibility. I'll disengage the coupling at the tranny and see if there's any difference. I'll post my results.

Without question, this maybe my prime opportunity to have it lowered and finally get a stable suspension. I just wanted to know the primary cause first.


I've replaced the front tie rods, but not the rears. Are their tie rod ends at the rear?

I need to check/retorque those CV joints anyway. I'll let you know the results.


Thanks for all of the suggestions. I'll post what I came up with asap.

Ken

Rassel

How long ago did you do a wheel alignment?
What tires do you have?
Have you tried with a different set of tires?

993Porsche

The alignment was done about a month ago.
I'm using Toyos' T1R and they are in great shape.
No have tried different set of tires. I will put that on the list too.


Thanks,

Ken

Felix

Is it only when accelerating and not at steady speed?

993Porsche

Yep, that's correct or a least that's what felt.


Ken

Felix

I'd look for wear in a bearing, CV joint or mounting

CarmG993

What about wobble or 'chatter' on deceleration?

ppressle

138k with stock shocks???

I had a huge rear wobble in my car over slight bumps when cornering with 30k on the stock shocks. Replaced with pss9s and it is quite well planted now.

What is the frequency of this noise/vibration? Engine speed? Wheel speed? Suspension speed?

If it is suspension resonance speed, I would start with the shocks (and at least m030 springs)

Pete

993Porsche

I'll check the bearings and CV joints, but what do you mean "mounting?"

The wobble is only on aceleration and no chatter.

Wobble over speed bumps. Yep I get that too.

The frequency of the vibration is during the range of 50 to 65 mph. It evens out after then. The engine speed during that range is I guess about 4000. Never really looked at the tach when it happens. Not sure how to measure the suspension resonance speed. Can you give me an idea?

I'll test for the bearings/run out tomorrow. Then post my findings.

Thanks everyone.