Rear howl at 40 - 50 mph

[Smellybox]

Hey guys

I have a 03 2500 HD 2 wheel drive with a 6.6 LB7.

I have noticed when I get my truck up to 40-50 mph and let off the throttle I get a howl coming from the rear of the truck.

When I get back on the throttle even very lightly the sound goes away and letting off it immediately comes back.

Any ideas what it may be.

Thanks

Bryan

[Mark Rinker]

Doesn't sound good.

I'll assume that you have checked to see that there is lube in the rear diff. If a pinion seal has gone away, you can lose all the lube pretty quick. When was the last time it was changed?

We run synthetic in all of ours and try to change them out every 50K. My 2002 is noisy after we let it get low when a seal went away. Better get under there and figure out whats wrong - pronto! :eek:

[Smellybox]

Well i did notice a little bit of oil in behind emergency brake area on the rear drivers side when we did the brakes. It was not alot of oil at all, not like it was leaking on the ground, so I didnt really worry too much about it. Would that leak be the pinion seal that you mentioned?

Thanks for your help.

Bryan

[Mark Rinker]

Thats the axle seal - another potential leak. Pinion seal is where the driveshaft enters the rear end housing, it will leak much faster when worn out. Better get things fixed or you'll be in for real expensive repairs soon.

The noise on deceleration on our 2002 hasn't gotten better or worse since, but I keep a closer eye on the rear end fluid levels as a result of that experience.

[cduramax]

I had the same problem at 50,000 miles. I noticed oil leaking around the parking brake. GM replaced the axle seals and bearings and the parking brake pad at the time. I looked back at the cost it was $825.00 with fluids.

[Smellybox]

cduramax,

did you have the howl also?? aside from leaking axle seals.

Thanks guys for your posts

Bryan

[cduramax]

No,

But I typically run mud tires and they tend to over power any truck noises. So it could have been making a noise but I may have not noticed.

I just noticed oil around the rear parking brake when I was changing the fluids in the rear diff. GM stated that the rear seals were leaking and while they were there they might as well change the bearings on both sides so I did.