
Originally Posted by
C-grunt
I got a buddy that is a mechanic for a big Chevy dealership. He says those trucks are overall very good vehicles. However the first couple years of the current generation truck had some issues with the V6 motor. I cant remember what it was but I believe it wasnt a major issue, but if the truck is a V6 maybe something to look into. But I dont think the 2019s have that issue.
The issue was the lack of fuel lubrication for the valves and more importantly, corrosion mitigation (especially in winter) as it's a GDI engine (LFX series). Some people were putting catch cans on them to help separate moisture and provide some top end oiling. In 2017/2018 they added an internal reservoir in the valley, so it's no longer and issue on '17 and newer (LGZ series). It's a pretty well thought out piece of kit and doesn't require draining like an aftermarket catch can.

Originally Posted by
Nocaster
I think the v6 was fine, but the early 8 speed trannies had issues. 2015-16. To my knowledge they are solid now. I was going to get one, but needed more room. So I bought a used suburban.
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That was an issue with torque converter shudder and was resolved by specifying a different ATF fluid for all the 8 speed autos. It also extended into the '18 production run. There were some other symptoms such as harsh low speed downshifts and "clunking", which for which reflashing the TCU was advised. They never did a recall, but there are a couple of TSB's covering them.
For reference, I have an '18 ZR2 V6/8spd. My truck has had both of the TSB's performed and has no more issues. Beyond that the biggest complaints center around the factory TCU programming, which causes a LOT of unnecessary downshifts at highway speeds, especially with the ZR2 which has more wind drag than the other trims. Even after the TSB's, my mostly highway 14 mile trip to work would have the trans downshifting to 7th and sometimes 6th gear 5-10 times, depending on headwinds. That's for a mostly flat trip with very little terrain or elevation change.
I bit the bullet and ordered a Trifecta Advantage+ tune, which reprograms the TCU as well as the ECU. It adds 19 lb ft of peak torque and up to 41 lb ft under the curve, which helps a lot. But the real advantage is the TCU shift programming, which is far superior to the factory program. Now downshifts at highway speeds on the same trip have dropped to 0, maybe a couple on really windy days. I figure that alone will do wonders for the longevity of the transmission, which doesn't get anywhere near "hot" temp wise (the DIC shows trans temp).
Sorry for the thread drift, but the current 3.6L V6 (LGZ) is solid. The one thing I have to add is that this engine was originally developed for the Camaro and Cadillac CTS. When they dropped it in the Colorado, they didn't bother to change the cam profiles. That means it's a high winding engine (7200 max RPM) that produces more HP than torque by quite a lot (308hp @ 6800 and 275lb ft @ 4000). It's kind of opposite of what works best in a truck for towing and hauling. It really lives best at 3,000-5,000 rpm. On the plus side, if you don't tow or haul much, it's surprisingly quick AND fast for a normally aspirated V6 truck. Pretty much everyone who's ridden in mine at WOT has been shocked how quick it is.
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