Ken_W

I just bought a 2002 2WD Avalanche with 145,000 miles and have a mystery squeak when driving slowly.

It starts when I put the truck in gear, give it some gas and begin to move, in either Drive or Reverse. As soon as I take my foot off the gas the noise is gone. If I stomp on the gas and accelerate hard, I don't hear it (but that could be that it's drowned out by engine noise) If I lift my foot from the gas it's gone.

At first it sounds a little like the wear indicator metal clip thing on a brake pad that's just begun to drag on a warped rotor - squeak.... squeak.... squeak.... and it gets faster and higher pitched as rpm's increase. The frequency is correlated to the engine speed, not to how fast the wheels are turning. As the engine revs up to the top of first gear, the squeak gets faster, becoming a squeal. When the trans shifts from 1st to 2nd, the noise stops for the brief second during the shift, and then starts when 2nd gear engages, but slower again. It then gets faster as rpms climb, becoming a high pitched squeal. I can't hear it anymore above 25 mph either because it stopped or because of the engine/road noise.

It only squeaks in the morning, after the truck hasn't been driven all night, and goes away after driving a few miles and the truck warms up.

It doesn't squeak when not moving. In park or in neutral I can rev the engine no prob. Shift to drive, foot on brake - not moving but giving engine a little gas, no noise.

It doesn't squeak when truck is rolling along in Neutral, engine on or off, engine revving or idling.

And it doesn't squeak when in drive coasting. As soon as I lift my foot off the gas - no squeak. Foot on gas - squeak, squeak, squeak.

So, I'm pretty sure it's not belts, pulleys, brakes, or wheel bearings. Does any of the above rule out U-joints? Can a transmission make this kind of noise? I've read this is the 4L60E. Any ideas, advice or suggestions on what it might be or how to go about diagnosing the specific source of the noise would be greatly appreciated!

sbower1976

I am not very experienced in this car yet but it does sound like a belt when it is under certain loads , If you have AC try turning that on or off and see what happens, another quick test could be to spray the belt with WD40 whilst the engine is running and then jump in and drive slow with the bonnet ( hood ) closed and see if the squeak has stopped. Is there a bearing somewhere between the gearbox and the diff that hold the drive shaft. Have you tried to slightly engage the park brake whilst slowly driving ?

avalancher66

You probably already fixed this problem. But I had the same thing. Replace all the u joints now im at 192000 strong

Ken_W

Sorry for not following up sooner. Had two separate garages try to diagnose the noise, first mechanic suspected it was suspension, wanted to replace the ball joints (nuts!), second mechanic said it was definitely the tran$mi$$ion. I knew the first mechanic must be crazy, and luckily, didn't have the cash for a transmission job, so I just kept driving it. The squeak got louder and more persistent, and when the truck started to vibrate at highway speeds, I took it to a third garage where they replaced the u-joints. Problem solved! You guys were right, I now know to ask all questions here first and also which two garages to never go to again. Thanks