2020 GMC AT4 3.0L/Massive Oil Leak

just to add to the list, i have a 2020 gmc siera denali duramax and the rear main seal blew. 6800mi
 
Seems like it's all 2020's in this thread so far?
 
SticksandSpades said:
Have a 2020 1500 Diesel with 11k miles. Rear seal blew while on a road trip 250 miles from home, engine light came on steady, reduced engine capacity, trans fluid up to 195 degrees, oil down to 18%, leaked all over, undercarriage/running boards all splattered. Towed to dealer, should have it repaired in 4 days they needed to have the part FedEx'ed. Apparently they are going to have it delivered to me back home. We will see. Hope that is the last of the problems.
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On the bright side. The fix they have is a sure fix now so you shouldn’t have any issues. But I sure would press for extended warranty or somthing
 
BoostN said:
Seems like it's all 2020's in this thread so far?
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Yeah I thought they had proper seal install figured out by 10/20 or so.
mines a 08/20 build with nothing yet. And no crank no start either
 
I have a 2021 GMC Sierra 1500 Elevation Diesel, 12k miles on it. Yesterday I had the truck out doing errands and when I came home, I noticed a 6-7” diameter oil spot on the garage floor. Checked the dipstick, nothing registered. No oil light came on either. This truck is not even 5 months old and this is the second major thing to go wrong. The first was the long crank. It took a couple of weeks for that fix, because they had to tear down the engine just to take a picture to send to GM to get permission to fix it, before they were allowed to order the part. And it did it again, only once, after I got it back. So you can add the 2021 truck to the list.
 
Could be the same issue previously reported regarding rear main seals. Some 6.6L has the same issue. Seems to be a part supplier quality issue rather than a design flaw. As for the crank no start, get them to also update the ECU.
 
Update-Very long story, I will try and make short here. Back in January 2021, I filled complaint against local dealer(Alfred Matthews, Modesto, Ca), they were horrific. I got a case number from GMC. My 2020 GMC AT4 3.0 had been in the shop over 20 days. I was disgusted with dealer and problems with 2020 GMC 3.0. The GMC complaint process is maddening, but I made it a hobby, to work my way through the process. Estimating 60-70 emails, 15-20 phone calls. I even emailed the CEO of GM. Aprox May, I got letter and phone call from GMC. GMC offering to buyback 2020 GMC or I could replace with another GMC truck. The repurchase process was long and had several stages, but yesterday(Nov 23), I dropped off my 2020 GMC AT4 1500 3.0 and picked up my 2022 GMC AT4 2500 Duramax. I had to pay the difference, between 1500 and 2500, but it was worth it. After the massive oil leak with the 2020 GMC 3.0 diesel, my MPG was less and the motor was really noisy. I didn't realize how noisy, until I drove the 2500 Duramax, Possibly some long term issues with the 2020 3.0 and I think GM knows this. Been a GM guy for over 45 years and I was losing faith in GM, but feel little better now. Good Luck and I hope this info helps out.
 
Granuts55 said:
Possibly some long term issues with the 2020 3.0 and I think GM knows this
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One bad motor/vehicle doesn't make them all bad. As a lifelong GM fan and diesel owner, people also lemon the 2500's as well. It just sounds like you got a bad one sadly.
 
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2020, 35,450 miles and zero issues with anything on the truck other than when I drove it home from the dealership. On the way home from the dealership the engine started to overheat due to a loose radiator cap.
 
Lgcorder said:
2021, 16k miles, lost rear main seal yesterday.
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Truck was down a couple of days. They followed the tsb and replaced the timing cover with seal pre-installed. Unfortunately, back in shop 2 weeks later with service 4wd light. Bad actuator was putting truck in 4wd instead what showed as 2wd. Hopefully that's it for the bad luck bc I have really loved this truck.
 
Lgcorder said:
Truck was down a couple of days. They followed the tsb and replaced the timing cover with seal pre-installed. Unfortunately, back in shop 2 weeks later with service 4wd light. Bad actuator was putting truck in 4wd instead what showed as 2wd. Hopefully that's it for the bad luck bc I have really loved this truck.
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Did the seal completely pop out of the timing cover? Just curious?
 
Granuts55,
I have a 2021 Silverado with the 3.0 Duramax. It's been in the shop for the past 30 days, and estimated lead time on the parts is 60 days from now. DEF issues. It has been in the shop twice before with the same problem. Truck has 18,000 miles on it. I also have a case with GM, but it feels I am just talking to an person who was put there to offer an empathic ear, not really do anything. How did you make the leap to someone with authority to actually do something?
 
I have a 2021 Denali, 4X4, 3.0. And with 6670 miles it is at the dealer for another oil leak. First was 3500 mile and was the rear main seal. Now it is coming from the front timing cover. This on not the best method for getting free oil changes!
 
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