could an under drive pulley cause a big vibration? it seems like every time i accelerate i get a vibration that gets worse with rpms, it gets alot worse when i really get on it.... thanks for the help

 

I need to mark this thread. My bro just bought a 98 TA and it seems to have a bad vibration just above idle to 4000rpm or so. this is noticed while car is in neutral or under load in any gear. It is an A4 with a mild crane cam (specs are a little milder than the hotcam). Headers seem to be clearing everything. Trannymount looks good. the stock harmonic ballancer looked bad...the rubber seperators are worn and when we took it off the 'layers' or sections of the ballancer were not aligned straight. We replaced with a brand new slp underdrive pulley. Just got the belt today.
Car still seems to have the vibration.

I have run the engine with and without the main drive belt on the car with both pulleys, Still has vibration. the a/c has been deleted as well.

We plan on unbolting the torque converter and pushing it back off the fly wheel to disengage the tranny from the engine and run the engine without the transmission and converter in the loop. This is the last mechanical test I know for atleast pinpointing the vibration as engine or tranny related.

All cylinders are fireing. HPTuners reports no codes nor anything out of normal.

The vibration is not like having a tranny mount up and die. The car can be driven. If an unfamiliar (not mechanical or not hot rod oriented) person where to drive the car they would not notice the vibration. They would just think the car was powerful and freak out when the tires spin so easily.

Gas is always premium, 92 octane.
the engine has 110,000 miles but is very strong and has not lost a drop of oil in 500 miles. K and N filter is fine and clean.
Motor mounts seem good. Engine does not 'torque free' or anything. they appear to be stock mounts.

Very strange.
You can feel it in the steering wheel. After noticing it you get a stronger sense for the vibration.

Warm or cold engine it will not go away.
As I said, we still need to disconect the torque convertor and see where that leads us.

good luck on your end.

 

ttttt

 

So i guess your vibration 'started' after installing an underdrive pulley?
How soon after?

We just got the new belt on and the bro thinks it is fine now...that the stock harmonic ballancer was indeed the source of the vibration. He thinks the new ballancer cured the problem. This is sorta opposite but similar to what you are experiencing.

Strange that know other people have experienced any thing like this...with or without it being on one of these cars.

 

well i just bought the car not that long ago, and it had an underdrive pulley on it so i was contemplating on whether or not that was it... just trying to narrow down the list

 

Check the transmission mount. I was having a lot of vibration and when I did the converter install my mount fell apart in two pieces. I replaced it and now have no more vibrations. That is more than likely the problem.

 

that is a good idea but i already know that it is not the problem, i have an poly eurathane mount and i just inspected it like a month ago when i upgraded my clutch.(it vibrated before that)

 

I get the same vibration on my car exactly around 1500-2000 RPM load or no load, I replaced the clutch with a Textralia, vibration still there,mounts seem ok. If I just got in this car and noticed the vibration I would think it is engine related possibly Harmonic Balancer, I'd like to see if it's common on these cars?

 

im having the same vibration, parked, just revving to 1400,,with both clutch in and out,,,,my crank pulley looks to be wobbly during these RPMs.

 

I have a vibration from 1800 - 2500 in park. The harmonic wobbles slightly on mine. Can feel it driving at 60 - 75 MPH Can't figure this one out either. Has headers, tci converter, poly trans mount, and 3.73's in a 98Z A4.

 

i have a vibration on my 99 6-speed, bad in neutral from just above idle till red line, feels like there a chunck of metal on one side slining wid the rpm of the motor, when excellerating its bearlly noticable but its there. idk what it is, motor bearly rocks, but like u guys my crank pully has a slight wobble. ??????

 

Anybody find a solution or anything helpful?

 

good times




j/k, i hate my vibs,, im pulling my plugs (just put in last year) tonight to see if anything shows up.

 

My car would do the same thing and I found out today that the drive shaft was just a little bit bent and at certain speeds it would start to vibrate a lot.

 

i wish mine was that easy,, mine also vibs in neutral, which kinda rules out the DS