2018 sierra 1500 6.2 stops revving at 5000 rpms

[Gagliano7]

Yesterday i went to pass a slow truck and when i hit 5000 rpms it just stopped going any further and felt like it was missing. Driving normal and accelerating up to 5000 rpms everything is normal. I tried one more time to see if it would happen again at a slower speed and it did it again. Seems to run totally fine besides wot. Trans shifts fine and i never had any harsh shifts from day one. I have had AFM turned off since it had 44 miles. I now have 26000 miles on truck. I did notice recently once in a blue moon it feels like i am running over rumble strips for a few seconds. Seems to happen when i am doing around 65 mph. Anyone have any similar problems?  Also no check engine light. Thanks

Edited December 29, 2022 by Gagliano7

[rav3]

Following 

Edited December 29, 2022 by rav3

[JimCost2014]

5 hours ago, Gagliano7 said:

Yesterday i went to pass a slow truck and when i hit 5000 rpms it just stopped going any further and felt like it was missing. Driving normal and accelerating up to 5000 rpms everything is normal. I tried one more time to see if it would happen again at a slower speed and it did it again. Seems to run totally fine besides wot. Trans shifts fine and i never had any harsh shifts from day one. I have had AFM turned off since it had 44 miles. I now have 26000 miles on truck. I did notice recently once in a blue moon it feels like i am running over rumble strips for a few seconds. Seems to happen when i am doing around 65 mph. Anyone have any similar problems?  Also no check engine light. Thanks

Do you stiil have the transmission fluid from the factory in it? If so, need to exchange it with the new Blue Label Mobil One that is used in the TSB for the 8 speeds.

[Gagliano7]

Still original fluid. Swapped throttle body just to see if that was the problem. Still the same problem.

[JimCost2014]

3 minutes ago, Gagliano7 said:

Still original fluid. Swapped throttle body just to see if that was the problem. Still the same problem.

Would get the fluid changed as soon as you can, especially if you are getting the rumble strip effect. I was getting that at 1500 RPMs, speeds from 45 to roughly 70. New fliud and it went away.

[rav3]

What Jim said

[Gagliano7]

Why would this all of a sudden happen? Does this mean every 25000 miles i have to change the fluid. I also noticed people that had the fluid changed only lasted a short time and started having problems again. I think it is time to get rid of this truck. I thought i was going to have this for at least 15 years. I thought the big worry would be AFM but now with the trans problems i think i am done with GM. 

[CamGTP]

Doesn't sound transmission related to me. The rumble and fluid stuff is whole different thing. Doing the fluid flush is a good idea for the torque converter and to me that doesn't explain the abrupt 5,000rpm hard limiter you are having.

[richard wysong]

I agree with Cam, Put a scan tool on it that does live data before firing the parts cannon and see what the problem is. It could be LOTS of things that won't light the CEL

[NWI Denali]

Sounds like some type of rev limiter you're hitting?

[steelerdude15]

Are you in drive or using the range selector and using a lower gear when this occurs?

[superdave160]

It's probably the rev limiter in the computer.  I purchased a tune from BlackBear Performance and I had to record a few WOT runs before the tune and I noticed that the RPMs didn't go as high as I expected.  After receiving and installing the tune, I had to record a few more WOT runs so that BlackBear could see if everything looked correct with the new tune installed.  During this run, the RPMs went way higher than before the tune.  

[Gagliano7]

Driving in drive. Never had a problem with WOT before. I go WOT at least once every 2 weeks. I was towing my trailer before this happened and it felt like the ride was rough in the truck the whole time cruising at 60 MPH. I thought maybe it was my trailer but it never felt like that before. My trailer is a 5x8 tractor supply trailer. Later when i had it loaded with wood probably around 1500 lbs

it felt better. I was thinking at wot something was going on with trans because it didn't feel like it was cutting out just being held back. I figured the torque converter may have been locking and unlocking. 

[Gagliano7]

those of you that had the rumble strip effect did it keeping getting worse before the fluid change? Now that i look back it was probably back in Sept when i first felt the rumble strip effect but i thought it was the road. Seems to do it a little more often now but some days nothing. My 5 year warranty is up in May so i need to go soon but i need my truck for the winter for my job so i would like to hold out until March. 

[Gagliano7]

Checked tune with HPTuners and the rev limiter is set to 6100 and rev limiter in each gear is 6000 rpms and 4000 rpms in neutral.

What parameters should i scan to see what could be going on. I can't tune my trans because you need to send it in to have it unlocked and pay $200 so i am not doing that. I should still be able to scan trans parameters correct?