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Discussion Starter #1
I have a 2019 ZR2 Colorado. I love the truck until I got the “shudder”. They replaced my fluids and all seems good. Now I have a issue with high Rmps and horrible mileage. My RPMS run at 2400-2600 when I drive 120km/hr. If I drive 110km/hr. My rpms run around the 1800-2000 which is normal. But if I hit a incline in the road my rmps shoot up to 24-2600 and once I hit the top of the incline my rmps continues to stay at 24-2600. I have to slow down in order for the rpms to decrease. Has anyone els had this problem. I need all the help I can get.
 

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Sounds like it is downshifting.... or do you think it is not downshifting but just slipping?
 
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I have a 2019 ZR2 Colorado. I love the truck until I got the “shudder”. They replaced my fluids and all seems good. Now I have a issue with high Rmps and horrible mileage. My RPMS run at 2400-2600 when I drive 120km/hr. If I drive 110km/hr. My rpms run around the 1800-2000 which is normal. But if I hit a incline in the road my rmps shoot up to 24-2600 and once I hit the top of the incline my rmps continues to stay at 24-2600. I have to slow down in order for the rpms to decrease. Has anyone els had this problem. I need all the help I can get.
It is normal for the transmission to shift based on demand. 110km/h (68mph) or 120km/h (75mph) on a flat road with steady speed should place you in 8th gear. If you are going up a hill trying to maintain the same speed (as if cruise control is on) then the transmission will downshift and the RPM's will increase. This is normal behavior. If at a steady speed you see your RPM's increase without downshifting then there is an issue.

As for hitting the top of the hill (assuming 110km/h (68mph) or 120km/h (75mph)), once engine load decreases while speed remains the same, the transmission should shift into top gear and the RPM's will drop. If transmission does not shift into top gear, try letting off the throttle to see if it goes into top gear. By this time you should be on flat ground and the speed should not drop significantly. You can then increase throttle and the RPM's should remain about the same.

Depending on the incline, the transmission might drop two gears.
 

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I have a 2019 ZR2 Colorado. I love the truck until I got the “shudder”. They replaced my fluids and all seems good. Now I have a issue with high Rmps and horrible mileage. My RPMS run at 2400-2600 when I drive 120km/hr. If I drive 110km/hr. My rpms run around the 1800-2000 which is normal. But if I hit a incline in the road my rmps shoot up to 24-2600 and once I hit the top of the incline my rmps continues to stay at 24-2600. I have to slow down in order for the rpms to decrease. Has anyone els had this problem. I need all the help I can get.
It's the electronics accelerator pedal,the pedal is not in sync with the motor reevyou have to buy an aftermarket accelerator booster chip modular then you can lead foot it properly ?
 

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Sounds like it might be learning still. Maybe give it 2-3k and see....

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When they do the fluid flush they also flash the transmission software. I noticed it adjusted the shifting so the truck wouldn't sit at lower rpms too often, especially on inclines.
 

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Discussion Starter #7
Sounds like it is downshifting.... or do you think it is not downshifting but just slipping?
I think it’s downshifting, they ran some tests on it and said my engine is running at 98% work load when the truck is empty. So not sure what is going on. It’s in the shop again right now but still no answers. They told me I should only drive 110km/hr all the time lol. What a joke. I am really not a happy girl. I have only 5600kms on it. So done with it lol
 

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Discussion Starter #10
It is normal for the transmission to shift based on demand. 110km/h (68mph) or 120km/h (75mph) on a flat road with steady speed should place you in 8th gear. If you are going up a hill trying to maintain the same speed (as if cruise control is on) then the transmission will downshift and the RPM's will increase. This is normal behavior. If at a steady speed you see your RPM's increase without downshifting then there is an issue.

As for hitting the top of the hill (assuming 110km/h (68mph) or 120km/h (75mph)), once engine load decreases while speed remains the same, the transmission should shift into top gear and the RPM's will drop. If transmission does not shift into top gear, try letting off the throttle to see if it goes into top gear. By this time you should be on flat ground and the speed should not drop significantly. You can then increase throttle and the RPM's should remain about the same.

Depending on the incline, the transmission might drop two gears.
It is normal for the transmission to shift based on demand. 110km/h (68mph) or 120km/h (75mph) on a flat road with steady speed should place you in 8th gear. If you are going up a hill trying to maintain the same speed (as if cruise control is on) then the transmission will downshift and the RPM's will increase. This is normal behavior. If at a steady speed you see your RPM's increase without downshifting then there is an issue.

As for hitting the top of the hill (assuming 110km/h (68mph) or 120km/h (75mph)), once engine load decreases while speed remains the same, the transmission should shift into top gear and the RPM's will drop. If transmission does not shift into top gear, try letting off the throttle to see if it goes into top gear. By this time you should be on flat ground and the speed should not drop significantly. You can then increase throttle and the RPM's should remain about the same.

Depending on the incline, the transmission might drop two gears.


I understand that but why should I have to let off the gas to make the truck shift into the higher gears. I have had a 8 gear transmission truck before and never have I had to let off the gas to let truck shift. I usually drive with cruise on when on the highway. My rpms will shoot up even if I am in cruise and on a flat road.
 

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Discussion Starter #11
It's the electronics accelerator pedal,the pedal is not in sync with the motor reevyou have to buy an aftermarket accelerator booster chip modular then you can lead foot it properly ?
Thank you I am going to look into that today. It’s still at the shop. I have to go talk to the guy today, so I am going to bring this up to him. ?
 

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Discussion Starter #12
I understand that but why should I have to let off the gas to make the truck shift into the higher gears. I have had a 8 gear transmission truck before and never have I had to let off the gas to let truck shift. I usually drive with cruise on when on the highway. My rpms will shoot up even if I am in cruise and on a flat road.
 

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I have a 2019 ZR2 Colorado. I love the truck until I got the “shudder”. They replaced my fluids and all seems good. Now I have a issue with high Rmps and horrible mileage. My RPMS run at 2400-2600 when I drive 120km/hr. If I drive 110km/hr. My rpms run around the 1800-2000 which is normal. But if I hit a incline in the road my rmps shoot up to 24-2600 and once I hit the top of the incline my rmps continues to stay at 24-2600. I have to slow down in order for the rpms to decrease. Has anyone els had this problem. I need all the help I can get.
Well, you are driving a brick and at 75 mph (approx. 120 kpm) you have a lot of drag to overcome.
 

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You have an issue if you are on a flat road with cruise control and your RPM's all of the sudden increase significantly. Either the transmission is slipping, or it is dropping a gear when it shouldn't. My truck will eventually upshift, but I have learned that if it is holding a gear when it should upshift, I let off the throttle until it upshifts. Then I adjust the throttle to maintain speed. If it is in the shop then hopefully they have been able to replicate it.
 

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So got the truck back. They still don’t know the cause of it. They have experienced what I was talking about but don’t know the cause. They told me for best fuel economy and rpms in the 1800-2000 rang it is best if I drive 105kms/hr. I have also learned to release the throttle so truck can shift But really I have never had a truck that you have to drive it this way. I have owned 8 speed transmission trucks before and have not experienced this issue. Even though I am continually told that this is just the way the 8 gear transmission works Lol
 

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So got the truck back. They still don’t know the cause of it. They have experienced what I was talking about but don’t know the cause. They told me for best fuel economy and rpms in the 1800-2000 rang it is best if I drive 105kms/hr. I have also learned to release the throttle so truck can shift But really I have never had a truck that you have to drive it this way. I have owned 8 speed transmission trucks before and have not experienced this issue. Even though I am continually told that this is just the way the 8 gear transmission works Lol
Did your dealership give you any diagnosis as to whether or not the transmission was downshifting when the RPM's increased? There are a few possibilities:
  1. Transmission is slipping
  2. Transmission is downshifting
  3. Tach is malfunctioning and the engine RPM's are not actually increasing
I would think your dealership should be able to tell you something other than "we don't know". Sounds like they don't want to tackle your issue. Since they have experienced the issue (make sure it is in writing), talk to the dealership's general manager and tell him/her you are going to open a better business bureau complaint if they don't fix your truck.
 

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Contaminated valve body possibly from a fluid flush, delayed shift or improper engine flare due to transmission issue. If it hangs at high RPM often when the engine isnt in need of more torque especially after getting over a hill or grade than there is a shifting issue possibly.
 

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I have the same issue Elisha with my 2017 ZR2 now that I got the shudder. The only difference is that I still have the shudder after a fluid flush and torque converter replacement. It will downshift now on the same flat highways with cruise control where it did not do it before the shudder. Pre-shudder it would be around 2000 rpm at 80 mph. Post-shudder it fluctuates between 2500 rpm to 3000 rpm at 80 mph. I have a significant decrease in my gas mileage, it rarely goes into V4 mode anymore, and has very poor acceleration now. It used to be my "sports truck" now it just feels sluggish like a Tacoma.
 

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What Elisha and Texas T have mentioned has made me think about computerish issues causing it. In doing some research solenoid came up. Sounds like it could be the issue. So after you have had the flush and/or torque converter replaced tranny drove worse. Your both don't say it is just in a certain gear, so to me would be the computer or information it is getting.
How Automatic Transmissions Work
 

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So got the truck back. They still don’t know the cause of it. They have experienced what I was talking about but don’t know the cause. They told me for best fuel economy and rpms in the 1800-2000 rang it is best if I drive 105kms/hr. I have also learned to release the throttle so truck can shift But really I have never had a truck that you have to drive it this way. I have owned 8 speed transmission trucks before and have not experienced this issue. Even though I am continually told that this is just the way the 8 gear transmission works Lol
Hey elisha,
Did your previous vehicle with 8 speed trans have afm on the engine? And the truck with the high rpms i think you have an option to run all 6 cylinders via sport mode or do you run that currently? Im starting to think 8 gear trans is to many gears for afm engine! Always switching gears too much work! Minus gm’s trans fluid mis hap and cutting back on torque converter!
Thank you and good luck!
 
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