Hi all looking for some help solving a harsh rattle mystery. Purchased a 2017 Suburban last summer with 110k on it and the transmission failed in October. Dealership partially paid for remanufactured transmission from GM. Weather started getting cold in MN in the fall and I noticed a harsh rattle noise coming from what appeared to be the transmission pan or transfer case. This happened throughout the winter on especially cold mornings. I could be paranoid but as you can hear from the video the noise is loudest in the transmission pan area.

Sounds like someone shooting a bunch of bb's at a metal pan.

Here's the mystery
The rattle noise is very loud with cold weather starts but I can't hear it once the truck warms up. I also cannot hear it when it's above freezing outside, only when it's really cold. If I start up the truck and drive off right away in cold weather, the rattle persists for a few seconds in drive and then disappears. I took it to the dealer last week and they really didn't know what it was and they replaced an exhaust clamp. Of course it was a warmer day when I brought it in and they could not replicate the noise. Temps dipped a little bit last night and I could hear the rattle again this morning although not as bad as it was over the winter.

Any thoughts? It's driving me bonkers!!

 

Did you ever figure out what your cold rattle was? I have the same noise on my 17 gmc Yukon only when below freezing and before transmission warms up. Sounds the same. I have dropped pan and serviced transmission without fixing the problem

 

make sure it's not a loose heat shield. See if the sound changes in 'D'

 

Does not appear to be a loose heat shield. Also I have not been able to find an external rattle from exhaust or heat shield. The noise will change/ vanish for a second when tapping transmission pan with rubber mallot. After a few minutes the noise always goes away and doesn’t come back until it’s been sitting in cold weather again.

 

I have tried to attach a video of the noise

 

sounds like a struggling pump

 

Did you ever figure out what it was, I have this same sound.