6.2L/8L90e Pulsing Vibration (not Chevy Shake)

L86 All Terrain · July 4, 2018

Hey guys I have a 2015 Sierra 6.2L/8L90e and it hasn't given me issue for the first 28,000km (17,000m) and just yesterday I started to get a weird vibration on the highway. It is like a pulsing vibration, comes on for 1 second then stops, then a few hundred yards down the highway it starts again for one second and will continue to "pulse" sets of vibrations in V8 or V4 mode.

If I shift into M7, (which disables AFM) it will not do it. But it will not do it in town in a lower gear regardless of V4 or V8, only in gear #8.

I have it booked in to get looked at tomorrow, just putting a feeler out to see if someone has had the same issue. I suspect it is related to AFM or the transmission, but was just checking here to see what I am looking at for a repair and confirm the issue if possible in-case the dealer "Can not reproduce the symptoms".

Thanks in advance.

L86 All Terrain · July 6, 2018

Truck would not do it for the dealer, so they asked me to drive the tech with the laptop plugged in. Would not vibrate again. He said "based on the symptoms you describe we would be changing out your torque converter." They left the work order open and told me to stop in next time it does it or video tape it if it happens after hours. They offered to change the converter but said it can get hard to push it through warranty without the symptoms showing up for the service tech to verify and not much sense opening the tranny up if it was a one time glitch, so I said I will drive it and see what happens.

Described it to my bud with a 5.3L/6L combo and he said his truck did it twice randomly in the 60,000km he has driven, but he traded that truck last week.

Doesn't look like any of you are having or had this happen. If you have, let me know how it played out in your situation.

AllenW2018 · July 6, 2018

I think I’m having the same issue. Sounds loud in the cab when it does it. Like a grind?

mjm-1957 · July 6, 2018

Does it feel like driving over rumble strips? Sounds like the beginning of TCC shudder. Extremely common problem with the 8 speed M5U transmission.Have your dealer check out TSB 16-NA-175 and they will probably replace the filter and change the fluid, update the calibration for the trans and do a fast adapt relearn.Good luck.

scott.moody.9401 · July 9, 2018

I had the same issue. Check the tach when this occurs. Mine had a 100-200 rpm jump associated with the vibration. Dealer flushed the trans and replaced the filter under warranty. Problem resolved

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