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Hi Everyone,

I just wanted to quickly introduce myself to the forum. I recently picked up a slightly used 2018 Colorado ZR2 crewcab with the 2.8L Duramax (22k mi.). I was looking for the ZR2 first and as I learned more I realized I would probably benifit most from the diesel option. I've had it for about 3 months now and so far I love it. I owned a 2014 Ram 1500 crewcab with the 3.0 ecodiesel and sort of liked it, I thought that vehicle was underpowered but I put roughly 120k miles on it in 3 years and it never gave me any issues and I got great gas milage, so I didn't hesitate to get another small displacment diesel engine in a truck! I've put about 3000 miles on this truck so far I average about 27mpg with mostly hwy driving.

Hoping to learn more about this engine/transmission and keep it running for a long time, I was happy to see a few posts showing some members with high milage rigs! Sadly i'm in CA so my tuning options are non-existant but I have no issues with the power the truck providies, infact I find it to be quite nimble on twisty mountain roads and moves when I need it to move quite nicely. I am a bit dissapointed in the transmission so far, a few annoyances i've noted:

  1. Driving down a steep twisty grade the transmission want to downshift and shoots the RPMs super high the minute any brake is applied. I think I understand what the truck is trying to do but it makes for a jarring / noisy descent at times. (I have a 2019 Express Van with the 3.6 and 8-speed transmission and it wants to do the exact same thing...must be a GM thing).
  2. The transmission temp seems to want to sit at 140* in most instances but i've caught it way up at 180* at times for no apparent reason under normal driving conditions - not sure if this is normail for the 6 speed mated to this motor, but it seems high to me. I have heard there is a plastic blocker plate on the ZR2s that restricts airflow and increases the transmission temp... need to read more on this to possibly remove it. Apparently it was added to reduce mud and other debris out of the radiator on the ZR2.
  3. If I am reversing and quickly stop and put the truck in drive and hit the gas I get some transmission stutter, not sure if it's a "problem" but I may consider flushing the fluid.
Talk to you all soon!
 

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Those transmission temps are normal.
pulling my toy hauler my truck sees 230
180 is normal. Remember the transmission cooler is built into the rad. So a hot rad from a hot motor will make the transmission run close to the coolent temp.
I hate when my truck does that downshifting and revs high. All you have to do is pull the shifter to low and use the shift buttons to set the transmission in 6th.
It will run and shift normal. But it will not do the downshifting while set like this. Just make sure it’s in 6th gear.
 

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Hi Everyone,

I just wanted to quickly introduce myself to the forum. I recently picked up a slightly used 2018 Colorado ZR2 crewcab with the 2.8L Duramax (22k mi.). I was looking for the ZR2 first and as I learned more I realized I would probably benifit most from the diesel option. I've had it for about 3 months now and so far I love it. I owned a 2014 Ram 1500 crewcab with the 3.0 ecodiesel and sort of liked it, I thought that vehicle was underpowered but I put roughly 120k miles on it in 3 years and it never gave me any issues and I got great gas milage, so I didn't hesitate to get another small displacment diesel engine in a truck! I've put about 3000 miles on this truck so far I average about 27mpg with mostly hwy driving.

Hoping to learn more about this engine/transmission and keep it running for a long time, I was happy to see a few posts showing some members with high milage rigs! Sadly i'm in CA so my tuning options are non-existant but I have no issues with the power the truck providies, infact I find it to be quite nimble on twisty mountain roads and moves when I need it to move quite nicely. I am a bit dissapointed in the transmission so far, a few annoyances i've noted:

  1. Driving down a steep twisty grade the transmission want to downshift and shoots the RPMs super high the minute any brake is applied. I think I understand what the truck is trying to do but it makes for a jarring / noisy descent at times. (I have a 2019 Express Van with the 3.6 and 8-speed transmission and it wants to do the exact same thing...must be a GM thing).
  2. The transmission temp seems to want to sit at 140* in most instances but i've caught it way up at 180* at times for no apparent reason under normal driving conditions - not sure if this is normail for the 6 speed mated to this motor, but it seems high to me. I have heard there is a plastic blocker plate on the ZR2s that restricts airflow and increases the transmission temp... need to read more on this to possibly remove it. Apparently it was added to reduce mud and other debris out of the radiator on the ZR2.
  3. If I am reversing and quickly stop and put the truck in drive and hit the gas I get some transmission stutter, not sure if it's a "problem" but I may consider flushing the fluid.
Talk to you all soon!
Ditto on what Coloradorob said on temps... totally normal. When towing I see 210 regularly, I'll just do a fluid swap more often to compensate. I think I may add an outboard cooler just to get the temps down a bit though.

I've played around with the 5th versus 6th gear when towing. I find for me most times that running in 5th gives better fuel economy then running in 6th. Only if there's a slight downhill in front does 6th prove to be better then 5th on the economy side of life and I notice my trans temps will drop a little 2 to 5 degrees with in 5th.
 

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Ditto on what Coloradorob said on temps... totally normal. When towing I see 210 regularly, I'll just do a fluid swap more often to compensate. I think I may add an outboard cooler just to get the temps down a bit though.

I've played around with the 5th versus 6th gear when towing. I find for me most times that running in 5th gives better fuel economy then running in 6th. Only if there's a slight downhill in front does 6th prove to be better then 5th on the economy side of life and I notice my trans temps will drop a little 2 to 5 degrees with in 5th.
I should have said 5th when towing.
I think 6th is to low in the RPM for towing and can cause damage. Under a load anything below 2k RPM is lugging a little 4 banger.
I have let mine shift to 6th while towing going down a long hill also.
 
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