2017 8spd transmission - ok to overfill?

[SkierMan]

Hi everyone,

I'm facing a perplexing issue with my vehicle's transmission and would appreciate any insights or advice.

Background:

• Had transmission filters replaced with Valvoline fluid at a local shop.
• Experienced delayed engagement leading to tire spins. The shop suggested the fluid level might be low and added more, which resolved the issue temporarily.
• Later, at a GM dealer, the transmission was flushed three times and filters were changed again due to concerns about the fluid type which I learned was critical.

Current Issue:

• On hilly terrain, experienced a loss of transmission engagement and a flashing CEL. After restarting, the transmission seemed stuck in low gear but we managed to move to safety.
• A similar issue occurred about a year later in hilly areas, with the transmission feeling like it might disengage but not like the previous experience a year prior.
• These issues don't appear on flat terrain.

My Theory:

• I suspect the transmission fluid level is critical, and the vehicle might be sensitive to even slight variations in this level which is supported by bits I read in other posts about getting the level correct.

Questions:

1. Adding Fluid on a Slope: If I park the vehicle on ramps adding angle to add more transmission fluid, would that help? Could this cause issues if the fluid is slightly overfilled?
2. Using Lubegard Additive: I came across Lubegard Platinum ATF Protectant, which claims to address shuddering issues. Is it advisable to add this to potentially slightly increase the fluid level? We do experience a harsh 1-2 shift, which was present before all the above started and the info on the Lubegard says their additive helps a bit.

Any advice or similar experiences would be greatly appreciated!

Thanks in advance!

 

[NickTransmissions]

Hi everyone,

I'm facing a perplexing issue with my vehicle's transmission and would appreciate any insights or advice.

Background:

• Had transmission filters replaced with Valvoline fluid at a local shop.
• Experienced delayed engagement leading to tire spins. The shop suggested the fluid level might be low and added more, which resolved the issue temporarily.
• Later, at a GM dealer, the transmission was flushed three times and filters were changed again due to concerns about the fluid type which I learned was critical.

Current Issue:

• On hilly terrain, experienced a loss of transmission engagement and a flashing CEL. After restarting, the transmission seemed stuck in low gear but we managed to move to safety.
• A similar issue occurred about a year later in hilly areas, with the transmission feeling like it might disengage but not like the previous experience a year prior.
• These issues don't appear on flat terrain.

My Theory:

• I suspect the transmission fluid level is critical, and the vehicle might be sensitive to even slight variations in this level which is supported by bits I read in other posts about getting the level correct.

Questions:

1. Adding Fluid on a Slope: If I park the vehicle on ramps adding angle to add more transmission fluid, would that help? Could this cause issues if the fluid is slightly overfilled?
2. Using Lubegard Additive: I came across Lubegard Platinum ATF Protectant, which claims to address shuddering issues. Is it advisable to add this to potentially slightly increase the fluid level? We do experience a harsh 1-2 shift, which was present before all the above started and the info on the Lubegard says their additive helps a bit.

Any advice or similar experiences would be greatly appreciated!

Thanks in advance!

Fluid level is important but it's not going to throw a CEL. Scan the pcm to find out what DTCs are setting and storing before doing anything else.

Also if you are experiencing shuddering, that is likely converter and lube guard will not help, if so. Wont help with your harsh 1-2 shift either.

 

[B-train]

If it's the 8 speed, make sure it was flushed with the new fluid. Shuddering is common with the original fluid. Also, level is critical. Been there, done that. Check at correct temp is key.

 

[SkierMan]

I've never experienced shutter, since new. The fluid exchange that was completed by GM, was with the updated recommended fluid, Mobil 1. They flushed it 3 times. It's been over a year since the problem occured where we had to coast over to the shoulder.

It was on a incline, coming to a yeild. When I attempted to go, the engine just free reved a few times. I think the transmission was going from 2 to 1 and it like it just missed. We were able to coast to the shoulder. I put the car in manual lockout, didn't do anything, hit the tow/haul to check temps, all good. Put it in park, reverse, etc. Turned off. Started again and then I was able to move with the CEL turned on in likely 2nd gear lockout. It wouldnt shift. After setting on level ground for an hour before we tried again, everything was fine. CEL was gone. I didn't have a code reader with me at the time, it was over 3 hours away.

We haven't had any issues since then. Except when we returned to that area over the weekend.
Can feel that the engine almost free revs for just a tiny tiny bit, maybe 100 RPM or so before the gear catches. I believe the issue is in 2nd gear, or maybe 2nd gear kicking down to 1st gear. If you asked my wife, she'd have no clue what I am talking about, but to me it's apparent and makes me anxious. Now that we are back home, no issues.

Is this the slipping that people refer to? Or the pump cavitating because it doesn't have enough fluid? too much fluid? It only has symptoms on steeper terrain.