When I put my '98 A4 in gear, I am getting a rumbling vibration. I can feel it in the steering wheel. It only lasts for a couple of seconds. It's worse with the A/C on. I replaced the belt tensioner when it first started doing this, it helped for about 6 months, then it came back. could I have another bad tensioner? Could it be the harmonic balancer? I'm pretty sure it's something that's running off the serpentine belt.
Any suggestions?

Mike

 

Anybody?

 

There is a TSB out on this condition. My 99 A4 had the same problem. The fix consists of replacing the alternator with a newer style that has a clutch on the pulley, the belt tensioner is also replaced and a PCM reflash is done. The vibration is from the main serpentine belt during transition from park to drive, reverse to drive ect. If you had the fix done then maybe the tensioner is starting to fail or the main belt needs to be replaced.

Tom

P.S. It took GM three tries and over a year to finally fix the problem on my car.

 

I think the dealer just replaced the tensioner. Does anyone know how I can get a print out of the TSB describing the fix so I can bring it to the dealer and save me a lot of hassle?

Thanks for the help

 

Mine does the same thing, replaced belt tensioner once, worked for about 6 months. Where can we get a print out of this TSB.

 

Here is the text of the TSB


Subject: Intermittent Accessory Drive Rumble Noise During Garage Shift and/or During Parking Lot Maneuvers (Install New Generator with Decoupler Pulley and Accessory Drive Tensioner)
Source: Chevrolet Dealer Technical Service Bulletin
Number: 99-06-04-029A

Models: 1997-2000 Chevrolet Corvette with 5.7 L Engine (VIN G -- RPO LS1) and 4L60-E Automatic Transmission (RPO M30)

This bulletin is being revised to update the correction procedure. Please discard Corporate Bulletin Number 99-06-04-029 (Section 06 -- Engine).

Condition: Some customers may comment on an intermittent accessory drive rumble noise when performing a garage shift and/or during parking lot maneuvers, such as turning the steering wheel to the lock position. This noise may also occur when turning on the air conditioning at idle conditions.

Cause: Engine idle speed may drop below 600 RPM while performing a garage shift, turning the steering wheel to the lock position, or turning on the air conditioning. This noise may be amplified by a large rate of change in engine RPM. This condition can also be aggravated by different low engine RPM driving conditions.

Correction: A new Generator with Decoupler Pulley and reduced damping Accessory Drive Tensioner was implemented for all Corvettes with automatic transmissions at 2001 SOP (Start Of Production). The generator with decoupler pulley is used only on Corvettes equipped with an automatic transmission. The reduced damping accessory drive tensioner is used on all 2001 Corvettes.

The new decoupler pulley generator and tensioner assembly should be used to service 1997-2000 Corvettes with automatic transmissions that exhibit the idle rumble noise. Refer to the Engine Electrical and Mechanical sub-sections of Engine in the Service Manual for generator and tensioner replacement

Parts Information:

Part Number
Description
Qty

10436674
Generator Assembly w/Decoupler Pulley
1

12568181
Accessory Drive Tensioner
1

 

Any idea on what this costs at the dealer?

 

My 97 does the same thing. The belt starts vibrating between the ALT and the water pump. Newer models have a clutch on the ALT to take care or this. It won't hurt anything, so I wouldn't worry about it.

 

I would put a ECS supercharger on it. They will replace the stock tensioner with a heavy duty one plus add 200 hp

 

had this done to my 99 vert at dealer 4 years ago. solved problem. no trouble since