Trog

Ok, this is a new one in my shop. It is NOT either tensioner as both are brand new & feel plenty strong.

It is an obvious belt "flutter" of the belt between the alternator & the power steering pulleys. Only at super low RPM (automatic car stopped in gear). You can literally SEE the belt fluttering & hear the awful rattle that sounds like the whole front of the motor.

I have replaced, tensioners (both), all idler pulleys (AC & Accessories), water pump (had a slight bearing movement), tried both a gatorback & a standard Gates brand belt.

Damper pulley looks good as in no big wobbles.

So, now I'm down to changing the alternator (easy) and/or power steering pump (not so easy). Both feel smooth without bearing play, both pulleys have been cleaned & grooves lightly sanded to NO effect.

Any thoughts or anyone seen this one? I've fixed quite a few squawks with AC tensioner & gatorback belts but this one is NOT responding to anything.

TIA
M...

grantv

1. Any chance one of the pulleys is not alligned with the others?
2. No wobble at all on HB?

Trog

HB isn't bad at all. I did find a TSB for this exact thing though...

#1, automatics had a TSB for chatter due to the low rpm that those run at, usually 550-650 rpm.

#2, GM TSB 99.06.04.029A covers this and says the following
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.


Also, there is a calibration update for the PCM to assist with idle stability.

Paul Wood

Just a thought and not intended to be a smart *** but are you sure the belt is properly routed? Can't imagine enough slack in the belt to shudder as you described at any RPM. Just a thought. Good luck sir.