2.5L I4 (6 speed Trn) versus 3.6L V6 (8 speed Trn)

gmcsierra71 · July 2, 2019

I have been trolling these forums for a few weeks now. Very interesting ( and disappointed) to see so many folks with the 8 speed transmission problems. I am somewhat interested in buying a GMC Canyon and would love to have the V6. However, after seeing all these 8 speed transmission problems, it seems one would be better off buying the 2.5L I4 with 6 speed transmission. Any thoughts on the 6 speed transmission?

mjm-1957 · July 2, 2019

I am the transmission guy at a Buick GMC dealer, I can not count how man transmission problems I have seen with the 8 speeds in these trucks(Canyon-Colorado). I have only done 1 six speed in a diesel Canyon that the guy was towing bobcats and excavation equipment with and it lasted 67,000 miles.The 8 speeds were bad from the get go. All these experts on this forum swear that the new ones are improved- don't believe it. If you buy one get an extended warranty on it.That truck is insanely difficult to work on also. Wait till you have to replace a starter on the V6, warranty time is around 5.5 hours....

carloliveira · October 15, 2019

I currently own a 2018 Colorado Crew Long Bed V6 and the transmission at first was quirky, funny shifting behaviours stay in too low a gear, and adapting to my very careful driving behaviour during the break in period first 500 miles, I do not have the shudder and my build date is December 2017, in my experience driving the vehicle like an everyday bastard after the break in period yielded a more confident result than my first 500 miles. I'm currently at 5200 miles and ignoring the MPG gauge on the DIC to see how many MPGs I can get is no longer a concern because I discovered in an attempt to baby the vehicle to save gas caused the transmission to adapt to DRIVING MISS DAISY......I havent had any issues and I havent done any bulletins....if I was to be a cry baby and complain about something just to complain I would say the only thing I currently notice is during a slow down to full stop it appears the transmission downshift from 2nd to 1st you feel it but after spending so long looking for a problem I discovered driving my 2006 Nissan Xterra with 147000 miles and a rebuilt transmission at 139000 miles does the same exact thing and it's a 5 speed transmission....its minor at best.....with all this said there are known issues with other owners Colorados, I guess I've been very lucky so far, but overall I'm very happy with my unit. I almost wonder with all the awareness circling the 8 speed are some LOOKING for problems and being finicky in some cases? Are users driving the vehicle so awkwardly that the adapt feature in the TCM causes erratic behaviors? I'm almost certain after my first 500 mile experience that it can be possible in some cases.....

flyingfool · February 24, 2020

yes the 8 speeds are a time bomb from what ive read in the silverado forums. they need better software tuning also. bushings get destroyed and torque converters fail, stick with old reliable 6 speed

i run the 6 speed in my silverado 1500, and an NPR isuzu 4500 and sierra 2500 HD 6L80E/90E is the way to go!!!

Edited February 24, 2020 by flyingfool

newdude · February 25, 2020

On 7/1/2019 at 10:08 PM, gmcsierra71 said:

I have been trolling these forums for a few weeks now. Very interesting ( and disappointed) to see so many folks with the 8 speed transmission problems. I am somewhat interested in buying a GMC Canyon and would love to have the V6. However, after seeing all these 8 speed transmission problems, it seems one would be better off buying the 2.5L I4 with 6 speed transmission. Any thoughts on the 6 speed transmission?

The only "real elephant in the room" is the shudder. If you are buying a brand new truck, they more than likely are filled from the factory with the newest version of Dexron HP fluid and should give you no issues. The internet is a small pool of all owners of GM trucks (or any truck brand for that matter).

6 speed has its quirks/problems. We've been putting torque converters in 1500 Silverados with 6 speeds, a couple brand new 2019 1500s got ripped into for shift issues. I'd almost be willing to say the 8 speed other than the fluid change where I work has been a stronger unit than the 6 speed, with the 10 speed beating them both out.