Hesitation from 1st 2nd gear

[Wayne Garske]

Have a 2018 GMC Canyon 3.6 SLE that has a minor issue shifting from 1st to 2nd gear after first drive in the morning.  Back out of the driveway then start forward, no problem. Then after stopping at the corner stop sign 1/4 mile away the truck hesitates for a brief moment before shifting to second gear if I take off quickly after the stop. Hear a clunk noise but it shifts.  If I take foot off break, start rolling forward then press the accelerator it seems fine.  After initial stop it is not an issue. Just the initial start / stop. 

 

I have owned multiple GMC / Chevrolet cars and trucks off and on in my life.  Has a 1989 Chevy 1/2 ton, same issue.  Had a Camero, same issue.  I saw another post here that mentioned that GMC and Chevrolet have this "design" anomaly and not much can be done.  I think this is true. But other than this small issue I really like my Canyon, no other issues.  But starting to make me think. I just today received a letter from a "Lemon Layers" group out of Los Angeles about a pending case (#831186) against GMC trucks, mine included.  Lots of issues it seems but don't most vehicles have some sort of issue these days?  

 

My question, what would you do?  Live with it or sell it?   

[newdude]

Normal characteristic of the 8 speed.  I'd live with it.  

 

#16-NA-361: Information on Transmission Harsh 1-2 Shift Upon First Start Up/Shift of the Day Under Light Throttle - (Jan 26, 2022)

 

Condition

Some customers may comment that the transmission exhibits a harsh 1-2 shift on the first shift of the day, typically under light throttle.

 

Cause

This condition is due to the initial clutch fill time of the 2-3-4-6-8 (C4) clutch.

 

Information

Some customers may experience a flare condition on the first 1-2 shift of the day or after the vehicle has been parked for several hours. The condition may have developed after the replacement of a complete transmission assembly or the replacement of the stator support to correct a delayed engagement condition. This is most likely to occur under light throttle conditions. Subsequent 1-2 shifts have acceptable shift feel. Replacing transmission components will not correct the condition.  

 

Correction

Important: Replacing transmission components or complete assemblies will not improve the condition.

 

The first 1-2 shift of the day may be harsh. The customers’ vehicle should be compared to a like vehicle under the same driving conditions. Do Not replace any parts for this condition.

Note: This condition will not impact the designed performance or reliability of the vehicle.

Edited July 13, 2022 by newdude

[customboss]

Wayne, my newer 8 speed behind the 22' LTD Trail Boss custom 2.7L turbo 4 was starting to do what you describe but faintly at about ~11000 miles.

 

I suspected the GM Mobil1 HP ATF was giving up the ghost viscometrically and thinning a bit. I changed to Amsoil ATL with my dealers blessing and used their BG machine to change it out at 14000 miles or so.  I have a bit less than 1000 miles on the Amsoil ATL and have tried to force the issue and it's gone. As a matter of fact the downshifts and upshifts are more positive but still super smooth.  I think better than before with OEM M1 HP ATF. 

 

Can't say enough positive about Nick and  https://www.gm-trucks.com/forums/forum/139-synthetic-advantage/ where I sourced my fluids, shipping was free and I got the products in 2 days here in Colorado ( shipped from Wichita KS via UPS).  

 

 

 

 

 

 

[customboss]

3 hours ago, newdude said:

Normal characteristic of the 8 speed.  I'd live with it.  

 

#16-NA-361: Information on Transmission Harsh 1-2 Shift Upon First Start Up/Shift of the Day Under Light Throttle - (Jan 26, 2022)

 

Condition

Some customers may comment that the transmission exhibits a harsh 1-2 shift on the first shift of the day, typically under light throttle.

 

Cause

This condition is due to the initial clutch fill time of the 2-3-4-6-8 (C4) clutch.

 

Information

Some customers may experience a flare condition on the first 1-2 shift of the day or after the vehicle has been parked for several hours. The condition may have developed after the replacement of a complete transmission assembly or the replacement of the stator support to correct a delayed engagement condition. This is most likely to occur under light throttle conditions. Subsequent 1-2 shifts have acceptable shift feel. Replacing transmission components will not correct the condition.  

 

Correction

Important: Replacing transmission components or complete assemblies will not improve the condition.

 

The first 1-2 shift of the day may be harsh. The customers’ vehicle should be compared to a like vehicle under the same driving conditions. Do Not replace any parts for this condition.

Note: This condition will not impact the designed performance or reliability of the vehicle.

Initial clutch fill can be improved with a more  stable synthetic fluid, why they went to Mobil1 HP ATF.  The Amsoil ATL is even a better syn base oil and it shows in my Trail Boss 8 speed. 

 

Thanks for sharing all that newdude.  Your contributions here appreciated. 

[diyer2]

I had to chime in here. Switched to Amsoil fluids for an ATV and a 19 Hyundai Santa FE. No doubt it was an improvement in transmission performance.  

[customboss]

1 hour ago, diyer2 said:

I had to chime in here. Switched to Amsoil fluids for an ATV and a 19 Hyundai Santa FE. No doubt it was an improvement in transmission performance.  

Chemistry quality matters!