Strange vibration

[Drscope]

I have a strange vibration on my 87 that shows up under accelleration. It feels like the rear wheels are badly out of balance and it makes the shifter jump a bit.

Different wheels and tires on all 4 corners made no difference.

Any idea what to look at?

[rick13]

Repack CV joints. It may or may not be the problem, but it couldn't hurt.

[Rasta Monsta]

Motor mounts?

[guru944]

Drscope;

Strange, last night mine started to have some the vibrations as if wheel nuts were loose. Driving locally. Check the rear left wheel with torque wrench, all is tight. Probably the same thing. See if i can get to them this weekend.

Car sat for 2 yrs for repairs and upgrades.

Later...

[Drscope]

I've had a few different sets of wheels and tires on the car and the vibration is still there.

I've had several 944's over the years and none of them ever felt like this.

I doubt it's CV joints. It doesn't make the usual knocking noise when turning that you would get from a dry CV.

Maybe it's motor mounts, but again I've had bad mounts in the past without this vibration. Anyone have any good suggestions on ways to check them other then the obvious are they broken?

It just really feels like a badly out of balance wheel or out of round tire on the rear.

I was hoping someone could suggest something I haven't thought of yet.

[GreenWater]

Wheel weights came off the wheel and they are actually out of balance?

I would guess it isn't the motor mounts, mine are wore out and my car doesn't shack under power, only at idle.

Is there any sealant in the tires? Like slime?

Unless the fluxcapacitor is broken. That can cause all kinds of trouble.

[Jrboulder]

Originally Posted by GreenWater

Unless the fluxcapacitor is broken. That can cause all kinds of trouble.

Muffler bearing.

[mytrplseven]

Do you have the rubber center clutch? I'm also wondering if you've had a rear shock self destruct.

[GreenWater]

I am thinking you have a serious squeaky hatch problem. ha ha Just kidding.

Could there be a problem with the transmission? This maybe a stretch, but how about a gear that is severely worn. I am thinking of the ring and pinion gears. If they are worn bady and under normal power they are not slipping but under enough power the gears are not properly seating into each other and are kind of jumping around making the shaking in the car and also causing the shaking in the shifter. Just me imagining out loud.

[968 GUY]

Transmission mount? Loose CV joint bolts? Clutch slipping?

[rick13]

Did you even inspect the CV joints? Grab hold of the half shafts and give 'em a good shake.

[Drscope]

CV joints seem to be in good shape. I have not taken them off, but there isn't any sort of unacceptable play in them.

Transmission mounts appear to be OK, no movement when things are pryed on.

I suspect the car has the rubber center clutch, but don't know for sure. Past experiance with them is you can feel slop in the drive train when they start to go. This car when in gear and parked doesn't seem to have any excessive play like that.

I have had several 944's and never experianced anything like this before with any of them.

It's been the same even though we have had a few different sets of wheels, tires on it. So it's NOT a wheel balance issue or slime in the tires.

We've had the car for about 2 years now and it was like this when we got it. It has NOT gotten any worse, but it is an annoyance simply because I can't find the source!

When we bought it I figured it was simply wheel balance. So the old tires on phone dials came off and another set of tires on Fuchs went on. Still the same. Those tires were of unknown age, and the Fuchs really weren't the right size, so in short time another set of Fuchs were obtained, new tires were installed, everything was computer spin balanced and the vibration remains.

I have also installed another set of wheels and tires from a 911 and it is still there.

So with all those different sets of wheels and tires I'm fairly confident I can rule out wheel/tire balance.

Rear wheel bearings are good. No play.

Rear shocks are maybe a little squishy for a track car, but are still doing their job for a street car.

I just don't know where else to look.

I'm starting to suspect a torque tube issue.

[Rasta Monsta]

Originally Posted by Drscope

CV joints seem to be in good shape. I have not taken them off, but there isn't any sort of unacceptable play in them.

CVs can't be effectively inspected without disassembly, IMO.

On the other hand, could your R&P be on the way out as suggested? Drain & check gear oil for chunky bits?

[kdjones2000]

For a track car, I am guessing that it's the rear transmission mount. Stock they are floppy and when you get on the power the rear drivetrain starts moving all over the place, making the shift handle move.

Modify yours, or try a semisolid or full solid mount and see if that's the problem.

Good luck, Keith