transmission issue

mfbearded · July 31, 2021

got a 2019 trialboss....47000 miles. recently i noticed a shifting issues. seems more apparent at cruising speeds, like around town, residential areas. its not a clunk or jerk but almost like a delay or lag. so i called dealership yesterday and happen to talk with the service manager and he told me to bring it down to have it reprogrammed. i initially was a little perplexed and questioned him and he said hes not seen many issues with the new transmission and that with how heavily integrated these trucks are with electronics thats his bet on the issue. he said most issues that he comes across of this nature are a software update, not an actual mechanical issue. for curiosity i drove the truck down the street in manual mode and i felt like it was not as apparent. Any of this sound familiar to anyone or have any experiences with this. thanks all

Bamacommander · July 31, 2021

Is it an 8 speed ? They have been known to have some issues.

diyer2 · July 31, 2021

A site search or Google would have answered your question.

winks79 · July 31, 2021

More than likely need the fluid flushed and replaced. Had my done at about 5k miles. Cured my problem. The dealer should know all about this already. There is a bulletin on it for the fluid replacement. Gm is aware of the issue with this.

Chevrolet1 · August 1, 2021

Occasional harsh downshifts during deceleration = TSB 19-NA-244. Resolution is reprogram the TCM.

Shake / shudder during light acceleration = TSB 19-NA-121. Resolution is to flush fluid and install latest high perf. fluid.

My 2019 with 5.3L & 8-speed had these two symptoms. Dealer verified symptoms and applied resolutions, now it shifts great with no issues. Hope this info is helpful.

SilveradoRST · August 1, 2021

14 minutes ago, Chevrolet1 said:

Occasional harsh downshifts during deceleration = TSB 19-NA-244. Resolution is reprogram the TCM.

Shake / shudder during light acceleration = TSB 19-NA-121. Resolution is to flush fluid and install latest high perf. fluid.

My 2019 with 5.3L & 8-speed had these two symptoms. Dealer verified symptoms and applied resolutions, now it shifts great with no issues. Hope this info is helpful.

What was your build date if you don’t mind me asking?

Wiggums · August 1, 2021

I have a 2019 with the 5.3 and 8-speed. I had that done too and it seems to have helped. I still have the morning clunks from cold starts, that part seems incurable.

Grumpy Bear · August 1, 2021

1 hour ago, Wiggums said:

I have a 2019 with the 5.3 and 8-speed. I had that done too and it seems to have helped. I still have the morning clunks from cold starts, that part seems incurable.

U joints are good, right? Try heavy fibered grease on the transmission yoke spline. Check diff backlash. IF excessive a slightly heavier diff oil will help.

Spline grease worked on mine.

Wiggums · August 1, 2021

54 minutes ago, Grumpy Bear said:

U joints are good, right? Try heavy fibered grease on the transmission yoke spline. Check diff backlash. IF excessive a slightly heavier diff oil will help.

Spline grease worked on mine.

Eh, I'm no mechanic but I had that issue since the day I bought it, could it be bad from the factory? I had the dealership look at it, reprogram it, and the guy in charge said there was a TSB on it. That was a year ago and I don't think there was that much of a difference in cold starts, but it's a lot better after it's warmed up. Could it be bad from the factory? I know it's over two years old, but it has only 6,000 miles on it.

Edited August 1, 2021 by Wiggums

Chevrolet1 · August 1, 2021

13 hours ago, SilveradoRST said:

What was your build date if you don’t mind me asking?

Decal says Aug 2018

Chevrolet1 · August 1, 2021

3 hours ago, Wiggums said:

I have a 2019 with the 5.3 and 8-speed. I had that done too and it seems to have helped. I still have the morning clunks from cold starts, that part seems incurable.

Mine occasionally has this symptom as well, but not very often. It's covered by TSB 16-NA-361. Dealer instructions are: "Tell customer the first shift of the day may be harsh from 1st to 2nd gear. Compare the customer's vehicle to like vehicles. Do not replace any parts."

If I let off the brake pedal a little slower, or keep the brake applied just one or two seconds longer after putting it into gear, the symptom does not occur. Mine seems to occur if I do things quickly, which aligns with the TSB information about the initial clutch fill time.

Grumpy Bear · August 2, 2021

8 hours ago, Wiggums said:

Eh, I'm no mechanic but I had that issue since the day I bought it, could it be bad from the factory? I had the dealership look at it, reprogram it, and the guy in charge said there was a TSB on it. That was a year ago and I don't think there was that much of a difference in cold starts, but it's a lot better after it's warmed up. Could it be bad from the factory? I know it's over two years old, but it has only 6,000 miles on it.

:dunno:

Could be it wasn't greased from the factory

(spline)

Could be anything

Just gave you some ideas

Use what you can

Reject the rest

Wiggums · August 2, 2021

8 hours ago, Chevrolet1 said:

Mine occasionally has this symptom as well, but not very often. It's covered by TSB 16-NA-361. Dealer instructions are: "Tell customer the first shift of the day may be harsh from 1st to 2nd gear. Compare the customer's vehicle to like vehicles. Do not replace any parts."

I found that starting it remotely as I'm walking towards it then driving it when it's warmer alleviates the problem so I'm okay with that. Sometimes I forget and it lurches forward, it's more of a minor annoyance than a big issue to me.

econometrics · August 2, 2021

I have almost 18K on my Feb 2019 5.3L RST / 8spd. Just noticed this weekend some weird hesitations in my shifts around 30-45mph when I'm not on the gas very hard - but just lightly. I've learned to live with the 1-2 harsh shifts and the D-R-D clunks. But this is new.

The closest thing I can relate it to is when I had an older car and the engine misfired really quickly leading to a split-second RPM drop and lag.

I'm going to keep monitoring it. I never had the TSB fluid flushed on it, so maybe it's time.

Silverado4x4 · August 2, 2021

51 minutes ago, econometrics said:

I have almost 18K on my Feb 2019 5.3L RST / 8spd. Just noticed this weekend some weird hesitations in my shifts around 30-45mph when I'm not on the gas very hard - but just lightly. I've learned to live with the 1-2 harsh shifts and the D-R-D clunks. But this is new.

The closest thing I can relate it to is when I had an older car and the engine misfired really quickly leading to a split-second RPM drop and lag.

I'm going to keep monitoring it. I never had the TSB fluid flushed on it, so maybe it's time.

Yep you have the trans shutter, mine didn't show up till around 12,000 miles so I took it in and had the trans flush with the new updated fluid and now its as smooth as butter.