2014 GMC Sierra 5.3l 6 Speed Delayed Shifting

[Ryan Amey]

My truck has been having shifting issues and so far I haven’t really found anything on the internet that exactly describes what is going on. In the best way I can think to word it, here is what happens…

 

When cruising in the 50’s (mph) if I’m lightly on the throttle the truck will upshift but will have a delayed shift. The rpm’s will jump and then a clunk will follow once the gear engages. It happens every drive where I reach speeds of at least 45ish. When I count the gears out it seems like it’s between 5th and 6th which I recently learned that both are overdrive gears (at least that’s what I was told by a salesman who was selling in 2013). 

My truck has 109k and no mechanical issues on the car fax from the previous owner, I am the second. 

Any insight would be helpful, thanks!

[CamGTP]

Does anything change if the pull the shifter down into manual mode and select M5? This will only allow it to reach 5th gear and also disable the AFM system.

 

If it does then it might be related to the way the transmission torque converter functions with the AFM system. This is only a guess obviously but torque converter failures are pretty common with the 6 speeds.

[Ryan Amey]

22 hours ago, CamGTP said:

Does anything change if the pull the shifter down into manual mode and select M5? This will only allow it to reach 5th gear and also disable the AFM system.

 

If it does then it might be related to the way the transmission torque converter functions with the AFM system. This is only a guess obviously but torque converter failures are pretty common with the 6 speeds.

I haven’t tried that but I will and then let you know. I have already had the truck to the shop at around 90k to have the AFM system program removed. To the best of my memory this problem predated removing AFM though. 
 

 

EDIT: I just spent around an hour driving the truck in M5 and had no issues with shifting. 

Edited January 21, 2022 by Ryan Amey