Whining noise 2021 GMC Sierra 1500 3.0 Duramax

josh mcquown · July 25, 2023

I have a 2021 GMC Sierra 1500 AT4 3.0 Duramax, with 105,000 miles. I have recently noticed a whining noise that follows the engine RPM. I tried to access the idler pulley to verify its not the problem, but it's very difficult to reach. The whining does not sound like it's coming from the front or top of the engine bay. The whining sounds like its coming from the back, lower portion of the engine, where the transmission mates. My fear is that it's the engine oil pump that is sandwiched between the engine and transmission. There is a recommended oil pump belt replacement at 150k miles. Has anyone else experienced this issue? Has anyone done the oil pump belt replacement? I'm curious what it costs and if I should go ahead and have it done now and have the engine oil pump pulley replaced to avoid a catastrophic issue. I drive a ton, about 50k a year.

Any feedback, thoughts, solutions, etc are greatly appreciated!

josh mcquown · July 28, 2023

Turns out it was my transmission! I thought it was the engine considering it followed RPM. Guess I'll stick to woodworking.

Bikerjon · July 28, 2023

You can have it done when the tranny is out!

Ioniq MPG · July 28, 2023

I have this sound at 25k. Is/did your transmission get replaced? Any word on which component(s) in the transmission failed? Thanks in advance

josh mcquown · August 3, 2023

My transmission crapped out on the freeway last week. The transmission is currently being replaced with a refurbished unit. I'm also having the oil pump belt and rear main seal replaced while the transmission is out. My truck was out of warranty, but I contacted GM support and they are covering 70% of the transmission cost. So basically, the total is costing me what it would have cost to have the oil pump belt done. The oil pump belt was a fraction of what it should cost since transmission R & R is being covered.

I do not know exactly what failed in the transmission. The dealership is not opening the transmission since its being replaced. I doubt I'll ever know what failed.

If your truck is making a whining sound, I would take it to the dealer now so that if it fails outside of warranty you have documentation that you were concerned about the noise at 25K and a dealership inspected the noise.

How does your truck shift? I noticed a hard downshift while on the frwy, letting off the accelerator and on the brakes.