2025 Suburban 6.2L - rough shift 1st to 2nd gear

[Jongrreat]

Hi all,

Purchased a brand new 25 Suburban 6.2L Z71 a couple weeks ago. Pics below. Coming from an MDX, it’s quite the change but we love it! Only issue so far is that the shift from 1st to 2nd gear is rough/jerky, like it’s hunting for 2nd gear. The shifts in all other gears are no problem. If I accelerate slowly, then it’s smooth but, if I accelerate “normal”, then it happens. Only 900 miles on the odometer. I found two other threads on this forum for a 2023 and 2024 experiencing the same issue, but no resolution was posted. Some were saying the transmission is “learning” your driving habits and I hope that to be true but why is it only an issue for 1st to 2nd?
Thanks in advance!

 

[jfoj]

A few things.

1. Put the vehicle in L9 and see if anything changes. If may be possible the DFM system is doing something strange? Also try Sport or Towing mode and see what changes if anything.

2. I doubt you are tipping into the throttle far enough, but the 6.2l has an ignition timing map problem where it retards the timing close to 30 degrees when you tip into the throttle a bit more than normal. Some people refer to the sensation of a fish nibbling at the bait on your fishing line. Almost like a misfire.

3. The transmission valve bodies are a disaster on these vehicles. Many internal leaks that cause shifting problems. There have been people waiting for over 3 months for replacement valve bodies. Cannot say for sure this is part of your problems, but could be. I have all the parts to preventively correct any valve body problems on my vehicle, I plan on installing it soon on my 2024 and I only have 6k miles!

4. A halfway decent scan tool can monitor and display the shift timing. A knowledgeable person should be able to monitor the shift timing and determine if there is something unusual going on. This could possibly confirm a leaking valve body.

5. Although I hate AAMCO, call your local AAMCO and inquire if they offer FREE transmission checking with a scan tool. Some do, you might be able to have them take a look so when you go to the dealer you have more back up info.

6. The transmission is NOT learning your driving if the shifts are hunting or jerky. Now it may be possible that the transmission is shifting from 1st to 3rd. Again, a scan tool can monitor this as well.

Good luck and report back.

 

[Jongrreat]

A few things.

1. Put the vehicle in L9 and see if anything changes. If may be possible the DFM system is doing something strange? Also try Sport or Towing mode and see what changes if anything.

2. I doubt you are tipping into the throttle far enough, but the 6.2l has an ignition timing map problem where it retards the timing close to 30 degrees when you tip into the throttle a bit more than normal. Some people refer to the sensation of a fish nibbling at the bait on your fishing line. Almost like a misfire.

3. The transmission valve bodies are a disaster on these vehicles. Many internal leaks that cause shifting problems. There have been people waiting for over 3 months for replacement valve bodies. Cannot say for sure this is part of your problems, but could be. I have all the parts to preventively correct any valve body problems on my vehicle, I plan on installing it soon on my 2024 and I only have 6k miles!

4. A halfway decent scan tool can monitor and display the shift timing. A knowledgeable person should be able to monitor the shift timing and determine if there is something unusual going on. This could possibly confirm a leaking valve body.

5. Although I hate AAMCO, call your local AAMCO and inquire if they offer FREE transmission checking with a scan tool. Some do, you might be able to have them take a look so when you go to the dealer you have more back up info.

6. The transmission is NOT learning your driving if the shifts are hunting or jerky. Now it may be possible that the transmission is shifting from 1st to 3rd. Again, a scan tool can monitor this as well.

Good luck and report back.

Thanks for the detailed response!!! I think I’ll give it a couple weeks but, if nothing changes, will schedule a service appointment at my local Chevy dealer. Great idea about AAMCO / scan tool, will look into that.

 

[blanchard7684]

Hi all,

Purchased a brand new 25 Suburban 6.2L Z71 a couple weeks ago. Pics below. Coming from an MDX, it’s quite the change but we love it! Only issue so far is that the shift from 1st to 2nd gear is rough/jerky, like it’s hunting for 2nd gear. The shifts in all other gears are no problem. If I accelerate slowly, then it’s smooth but, if I accelerate “normal”, then it happens. Only 900 miles on the odometer. I found two other threads on this forum for a 2023 and 2024 experiencing the same issue, but no resolution was posted. Some were saying the transmission is “learning” your driving habits and I hope that to be true but why is it only an issue for 1st to 2nd?
Thanks in advance!

The first gear ratio is 4.7:1. So it is very jerky by its nature. I've noticed that the jerky response is more the throttle mapping than anything else. I have a 24 Suburban with 5.3 and first gear is a rodeo.

In a couple of weeks the learning aspect is already set in.

 

[jfoj]

I guess I will need to pay more attention to my 1-2 shifts before and after I modify my valve body. Not sure I have noticed anything unusual with the 1-2 shift, but I do agree the throttle behavior seems touchy when compared to my 2005 6.0l. Maybe it is because I have been driving the 6.0l for 20 years, but I do think the initial tip in throttle behavior is a bit jumpy on my 6.2l Yukon Denali. Maybe the engineers did this to make you think the engine is more powerful? I hate when stunts like this are rolled out.

I have noticed that I think the 2-3 shift seems to flare or be more prolonged than I would anticipate, almost like the shift time is delayed or there is a slight 2-3 slippage. I probably need to get my scan tool on the vehicle and monitor the 1-2 and 2-3 shift times vs higher gear shift times just to see what may be going on. Maybe this will change, be cured when I rework the valve body?