C4S. Any thoughts? I'm leaning towards tire rebalanced but confused by 4th gear pull.

I was on a 2 hour drive and passing I hit just over 80+ on a 70. I noticed in 6th gear the car started to shake massively after going above 3,000 rpm. Then I dropped it into 5th gear and same thing around 80+ and just over 3,000 rpm more shaking. Dropped into 4th gear and now doing around 65 again accelerate above 3,000 rpm more shake and wobble.

Just drove under 3,000 rpm the rest of the trip no problems in low rpm and lower speed under 70.

The wobble and shake reminded me of a back coil-pack on my old Audi 5 years ago when they had the coil-pack recall. But the bad coil-pack caused immediate rough running and shaking after start up.

I drove the next two days in the city fine with no issues but didn't want to push to hard because I needed to be places during this time. Drove home today and doing 70+ and no issues.

I want to be proactive but not just throw parts considering no cel's or anything just mechanical wobble. I just ordered new tires today .

The mechanic said and billed me for 6 new coil packs when he changed out the AOS 6 months ago.

 

Get the new tires in place, wheels balanced and check the result at high speed afterwards. That may be the cure.

Quote..The mechanic said and billed me for 6 new coil packs when he changed out the AOS 6 months ago.....This statement doesn't seem to fit into the equation.

 

If it's tire or suspension related you would feel it through the steering wheel as well. But it does sound like bad tires or a balance issue. It could also be clogged fuel injectors.

 

im guessing a tire problem, sounds like maybe u threw a belt in one of the fronts, hit any potholes lately?

 

You should be able to tell if it is engine related or tire related from the feel. It sounds to me like tires not engine. Engine trouble will not make the car feel dangerous.

Balance can definitely cause that and it could be made much worse with alignment trouble. Put the two together and you would feel very unsafe over a certain speed.

 

How is your clutch? Since you indicate it's over 3000 rpm's it sounds like it could be the clutch. However I would start with a good balance and have them check all the suspension components, including checking for a tire belt issue, have them check to see if the tires are true as well. As I mentioned before, if it is a balance issue you would/will feel the steering wheel going back and forth.

 

When you get the new tires. Have them throw your existing wheel and tire on the balance machine just to see. It takes just a moment of there time. It will help diagnose which wheel was out of balance if there is one

 

RPM shouldn't cause a tire shake. Speed and road conditions can bring out tire wobble/shake but rpm alone won't. However you can do 3,000 rpm in second gear at far lower speeds. If is shaking then, it's not the tires.

 

sounds like a balance issue but it could also be a bad wheel bearing . i had a bad bearing on my boxster make the same kinds of symptoms .

 

Had the same symptoms on my Audi as well, remedied with new coil packs. Have you checked the inside tires or rims? My turbo ran fine locally but over 50+ mph I experienced heavy shaking. Tires and rims appeared fine on the outside but under a lift... bent rims on the inside and blew a tire. Oh and the front strut mounts needed to be replaced. Long story

 

Thanks for all the thoughtful ideas.

It's cold in Seattle so I am driving the 4s a lot. Finally took out the c2 and have been driving around until I get the new tires mounted up and balanced. Such a lighter feel, so much fun.

I was also thinking the clutch but my experiences with clutches going out is just a loss of power with RPM's rising but the car is not going anywhere as fast. I was just thinking maybe somehow the clutch wasn't grabbing and causing the wobble.

C4 is driving fine again but haven't really had a place to drive over 70 without running into traffic.

I will update if it was just the tires needing to be balanced.