Rotational grind noise???

[chevyrider838]

At around 40mph and let off the gas, I hear a loud rotational grind that continues until speed decreases, then when I give it a little gas the noise starts again then disappears with increased speed. Sounds like it’s coming from the middle to rear of truck. Differential, transmission? Differential fluid was just changed‍. Have you had this issue and what was the fix? Any thoughts? 99’ K1500 Classic thanks.

 

[stutaeng]

Can you tell us if the truck was fine before? When did it start? How many miles? Everything is original?

Did you just buy it?

What year/cab configuration is it? 1500?

What did the differential fluid look like? Did you happen to look at the ring gear for any wear? It's pretty easy to check for backlash with diff cover off.

 

[chevyrider838]

Just started happening. I could hear noise slightly before but it’s gotten worse. 254k on the clock and stock. When replacing diff fluid and cover, the gears appeared to look good, however I’m no pro. Thx

 

[DonYukon]

So as Stuta said. whats the vehicle details?


I know on the Autotrac models equipped with the NP246 Transfer case theres a wear problem where the Pump eats into the housing of the transfer case. What I would define as your problem but that was my issue . yours could be different.

 

[stutaeng]

I was going to ask about transfer case, I hadn't seen if it was a C or K series. I was going to suggest a sprag in the transmission. I think there could be chatter marks developed in the races and then the elements start making noise.

But the transfer case could also be the culprit.

I would say remove rear driveshaft and spin it to that specific RPM/MPH. That will remove the differential from the possible problems, and you may be able to narrow down where the noise is coming from.

 

[HotWheelsBurban]

Have any of the u joints been replaced? My Burb is 2wd, but that noise sounds similar to what mine did last year when the u joints went bad( finally wore out after 200K).