[stlrammer]

I have a 2017 1SS with 24,000 miles, automatic transmission and I'm encountering a strange vibration/hesitation when torque from engine is gently applied going up a hill on cruise control or off cruise. Most noticed when applying small increases in torque such as when car encounters an incline or going up a steeper hill. Coming down hills even at high speeds (80 MPH+) reveals no vibration or hesitation at all. Going up the hill (even on a 60 MPH crawl) feels like 2 seconds of smoothness followed by 2-3 seconds of vibration (similar to hitting the edge of an interstate when it shakes to wake you up). I believe it's an engine or transmission thing but no "check engine" lights at all. Wheels are all balanced and alignment is spot on so uncertain of what is going on. If you have experienced this please advise.

[Scottyz]

I’m thinking torque converter issue when it’s applying or releasing. These auto transmissions are known for torque converter issues. May wanna read up on the issues in the transmission section on this site.

Now I can’t say I have felt this in a sixth Gen Camaro but by your description and the fact I’ve been a licensed auto tech for 25 years your description sounds like a torque converter issue. Only other thing I could think is a minor misfire the ecm can’t detect yet and therefore the check engine light isn’t on.

I’d put my money on the torque converter.

[caSStro18]

Originally Posted by stlrammer

I have a 2017 1SS with 24,000 miles, automatic transmission and I'm encountering a strange vibration/hesitation when torque from engine is gently applied going up a hill on cruise control or off cruise. Most noticed when applying small increases in torque such as when car encounters an incline or going up a steeper hill. Coming down hills even at high speeds (80 MPH+) reveals no vibration or hesitation at all. Going up the hill (even on a 60 MPH crawl) feels like 2 seconds of smoothness followed by 2-3 seconds of vibration (similar to hitting the edge of an interstate when it shakes to wake you up). I believe it's an engine or transmission thing but no "check engine" lights at all. Wheels are all balanced and alignment is spot on so uncertain of what is going on. If you have experienced this please advise.

Sounds like the dreaded A8 shudder. Well documented issue with the A8 transmissions. I’ve not experienced it but many people have this problem. Some get the transmission flushed and replaced with a newer fluid and it goes away. Others have the torque converter replaced and the problem goes away. Some have had all of these things done and the problem still persists. Take it to a reputable dealer. Your warranty should cover the repairs.

[wwiiavfan]

Yep, A8 shudder. I’ve had it, you are describing it spot on. Watch your tach closely as well, you might even see a little rpm fluctuation that coincides with the shudder.

[arpad_m]

OP, there is a service bulletin, number 18-NA-355, to address this problem. Visit your dealer ASAP and get it applied. The dealer should not ask any questions but perform this 1.5 to 2-hour procedure upon request.

If it does not fix the condition, you need to go back and get the torque converter replaced. Both the flush and the new torque converter are covered by the powertrain warranty, so you should be good either way.

The underlying story in a nutshell is that this is a known hardware+software problem with the A8 transmission from the beginning, it affects every GM car and truck that has this unit, and GM attempted to fix it in various ways with different fluids and revised torque converters earlier. The latest transmission fluid flush specified by 18-NA-355 apparently solves the problem for the vast majority of users. For those that went to the dealer too late and lived too long with the condition, the recurring shudder may have damaged the torque converter, so that may need to be replaced as well.

[Azerlazer26]

Originally Posted by arpad_m

OP, there is a service bulletin, number 18-NA-355, to address this problem. Visit your dealer ASAP and get it applied. The dealer should not ask any questions but perform this 1.5 to 2-hour procedure upon request.

If it does not fix the condition, you need to go back and get the torque converter replaced. Both the flush and the new torque converter are covered by the powertrain warranty, so you should be good either way.

The underlying story in a nutshell is that this is a known hardware+software problem with the A8 transmission from the beginning, it affects every GM car and truck that has this unit, and GM attempted to fix it in various ways with different fluids and revised torque converters earlier. The latest transmission fluid flush specified by 18-NA-355 apparently solves the problem for the vast majority of users. For those that went to the dealer too late and lived too long with the condition, the recurring shudder may have damaged the torque converter, so that may need to be replaced as well.

+1 This is your answer right here. Make sure when you take your car in they don’t take your car for a test drive. The largest TSB 18-NA-355 requires NO TESTING. Also please be sure to take your service advisor and do a through walk around with your car. When I went, they pushed my front fenders and cracked/indented my rocker panels due to hoisting the car incorrectly.

[stlrammer]

Thanks to everyone who diagnosed my car’s condition. SB 18-NA-355 torque converter. Should I drive it in manual mode until I get it in?

[Azerlazer26]

Originally Posted by stlrammer

Thanks to everyone who diagnosed my car’s condition. SB 18-NA-355 torque converter. Should I drive it in manual mode until I get it in?

Biggest thing is trying not to get the car to go into V4-V8 vice versa. One thing that I’ve heard is try to not drive in tour mode but rather sport or track mode. To answer your question, to avoid any further damage I would drive in manual mode.

[Homer2]

Originally Posted by stlrammer

Thanks to everyone who diagnosed my car’s condition. SB 18-NA-355 torque converter. Should I drive it in manual mode until I get it in?

yep.

[JCunningham]

get it right in its free and set an appointment for a loaner.