Strange Noise

[JohnnyR]

Need help diagnosing a noise on my 2005 2500HD Duramax/Allison, 78K miles. It's a squeak that only occurs at 44 MPH in 5th gear. Don't hear it as you accelerate, only after the it shifts into OD at 45 mph and I let it slow down slightly to 44 mph. Immediately goes away if you accelerate above that speed or if the transmission shifts down as you get below 44 mph. Not continuous, just short medium pitch squeaks. When I first heard it, I thought perhaps suspension related, shocks or springs. But if that were correct, seems it wouldn't just be the one speed and only in 5th gear. Seems to emanate from the tranny or further back but hard to pinpoint. Anybody else run into this or have guesses?

[More Power]

45 is a little lower than my Dmax shifts into OD - about 50 on a light pedal.

The squeak might be the exhaust system (hangers, clamps, etc).

Jim

[madmatt]

Sounds like it may be a u joint. only starts to squeak once the RPMs drop and the load on the drivetrain is lessened. Put it on a lift/jack stands and duplicate the conditions to pinpoint it.