A strange thing just happened to my car. I have owned it for over a year and have had no problems like this before. In fact I drove it this morning and it was fine then after work got in it and this happened. I showed up a mustang GT this morning on the way to work at 100 mph or so and the car was as smooth as always.

I took off tonight and under acceleration and above 3K I am getting a SERIOUS vibration through the shifter. The vibration feels like it is coming from the middle to the rear of the car. On a normal take off the car feels fine up untill it reaches higer rpm's.

The motor mounts have been replaced several years ago (about 50K miles) and the engine doesn't vibrate at idle or under load like when I turn on the A/C in neutral. The shifter does vibrate a little in neutral around 4K then smooths back out in the higer rpm's. The transmission is smooth shifting and makes no noise in gear or out while moving. The clutch is not slipping on quick take offs and was replaced about 50K miles ago too. Both axles were replaced about 50k ago too.

Could there be something in the torque that broke? Is there a bearing that could have gone bad just like that? Could the balance shaft belt have jumped a tooth and send the vibration back through the driveline?

Anyone have this problem before or any suggestions as to what I should check?

 

When my clutch was going bad I had strange vibrations through the shifter as well. Has the feel of the pedal changed at all?

 

My pilot bearing fell apart on me. The car could hardly be driven above 3k RPM. this lets the disc and drive shaft move about 1/4" off center. I hope that isn't it; that's the 1st part Porsche reaches for when they start to build a 944.

 

The pedal feels the same and engages at the same place. The only thing I have noticed is that at higher rpm shifts when I depress the clutch I feel a little vibration on the pedal. I will put the car in neutral and rev it with the clutch in and out and see if there is any difference in feel between the two.

By the way Russell, the chips are working very well. The engine is very smooth and the power band is wider than with my prev. chips.

Russell did you get a vibration that got worse at the rpm's increased and was it from the start or did it come on later in the rpm's?


PS Just checked with clutch in and out in neutral and rev'd engine. No noticable difference in vibration in shifter. It would appear that the condition only happens when moving. I don't believe it has anything to do with the transmission as the same thing happens in every gear.

 

Hope it's not your pilot bearing!!! The clutch will work just fine engaging and moving the car. It just vibrates like hell when you get above 3k in any gear.

 

Well, one other thing since you mention that it happens at the same RPM and with the clutch in or out makes me wonder about your balance shaft belts. Had them replaced lately?

 

I will get under the car today a start the inspection. It seems that if the balance shaft belt broke or jumped a tooth the engine with vibrate in neutral. This vibration/shaking only happens when I am moving so I a thinking about some type of mount or something in the torque tube. I hope it is not the pilot bearing.

 

Me too!!!!!

 

I got under the car and didn't see anything obvious broken. I took it for another drive and the vibration is coming from the rear. Over 3K rpm it starts and continues to vibrate with the clutch in or out. As soon as I shift to the next gear it goes away untill I get up over 3K rpm then continues even when I push in the clutch and the engine comes back down to idle. The problem only happens when in motion.

I did notice that there is a transmission mount on top and that I can move the transmission a little side to side maybe 1/4 of an inch or so. Is this normal?

 

Rock the tranny? or slide the tranny side to side?

 

The tranny should NOT be able to be moved AT ALL. This would indicate a shot tranny mount. I've messed around with two trannys in my NA, neither of them had any play what so ever (tried to shake the **** outta the first one as i though it was hitting the undercarraige.

 

Ah, I misread your first post, I thought it did it in neutral as well, which points to the engine. But if it's only doing it while moving it's a different story. You've got some good input here, especially the tranny mount check. Also check the bolts on your axle CV joints to the hub and tranny to make sure they are all tight, they sometimes get loose. I would also check the torque tube bolts to housings to make sure they haven't come loose. I hope it's not a bearing.

 

The transmission does move side to side just a little and I can see it moving in the mount. I can't push it hard enough laying on my back to make it hit anything plus the car was up on ramps. I am going to try to get it up on a lift this week. I will have someone in the rear looking at the transmission and put it in gear and accelerate.

If it was the bearing in the torque tube wouldn't that make noise all the time and it wouldn't go bad over a pertiod of time with a grinding sound?

Thanks for all the imput guys. I appreciate it.

 

I am back with the same problem but it is not quite as bad now. The vibration still comes through the shifter handle but has moved up in the rpm range to 3800 thru 4200. I can also feel it through the whole car. I have replaced the transmission mount with a solid one from Lindsey and that reduced about 75 percent of the vibration problem and the car is now drivable. I then replaced the belts/rollers/etc... and there was no improvement after they were installed.

I had the car at the track today and the transmission shifts fine and the clutch is working as it should. No noise from the torque tube either. The vibration did not get worse or make any more noise after 40 to 50 laps and a long drive home.

I looked at the motor mounts when I had the car on the lift this weekend and didn't see that either was flat or different than the other. Can a motor mount go bad without external signs of damage? The motor does vibrate some while at idle. I know the balance shaft belt is right as my friend who is the master porsche tech. at the dealership helped me or should I say I handed him tools.

Does anyone have any other ideas?