Talk:GM 8L90 transmission

I have a 2017 GMC Sierra 1500 crew cab 4x4 All Terrain pickup truck. It has the 6.2 liter engine with 8L90 8 speed automatic transmission. I bought this truck new. It's a secondary vehicle and not a daily driver. I primarily use this truck to camping, hunting, fishing excursions. I tow a 3500 lb. 18 foot travel trailer. At 2 years of age and 16,000 miles my truck began to experience the dreaded "Shudder". I noted that this event occurred at speeds under 70 mph while cruising at a constant speed and the transmission was in 8th gear. I noted that the shudder was intermittent (not constant), but regular. I noted that when the truck shuddered the tachometer would increase by 50 to 100 RPM. This indicates that the issue is likely related to the torque converter slipping as it's designed to do. The issue gets worse as the truck warms up to operating temperatures. Question is, why is it shuddering?

Being under warranty, I contacted by dealer. I've had a long standing history with this dealership and a good relationship with the service manager. I made an appointment and took the truck in. The service manager and I took the truck for a test drive and he experienced the same symptoms described above. He immediately knew what the issue was and knew what was needed to correct it.

The service manager explained that the transmission fluid was specifically designed for the 8L90 transmission. He advised that this fluid is hydroscopic (as most hydraulic fluids tend to be). Over time the moisture content in the fluid begins to affect the function of the transmission. GM's answer is to flush the fluid and replace with a different fluid that they believe is less hydroscopic.

I would highly recommend changing the fluid annually (flush and replace) to avoid causing damage to the transmission. I will personally change my fluid before any signs of issues arise. I'm not highly confident that GM is doing much to otherwise correct this issue.