6 speed or 8 speed transmission for 2018 GMC Sierra 1500 Crew Cab SLT 4X4

[Tiger427]

Hello All,  I am looking to purchase a new GMC Sierra 1500 Crew Cab SLT 4X4 and would like some advice on the transmission please. Which is better, the 6 speed or 8 speed transmission?

 

Thanks!

[mjm-1957]

I am the transmission guy at a GMC Buick dealer and I can tell you that more than 60-70% of my time is spent on the horrendous 8 speed M5U transmission. How GM could have put such a horrible shifting unit in such expensive vehicles is beyond me.Don't misunderstand, I do plenty of 6 speed 6l80 and a few 6l90's but usually they are high mileage units or in the case of the 6l90's are in heavy commercial applications with no maintenance to speak of.The 8 speeds are bad from day one. Just my two cents....

[Larry Broseh]

I agree with mjm-1957.  I have the 8 speed in a 2018 Silverado and and a 2015 1/2 Cadillac Escalade.  Same problem from day one with both vehicles-the gears are not only rough, they slam into downshifts when applying brakes enough to make the vehicles lurch forward.  Not consistent, unfortunately, unless you are in heavy traffic ranging from 20-40 mph.  It's bad enough it has started my u-joints popping at 5,500 mi. on my Silverado.  My Escalade had to have a torque converter replaced at 20,000 miles-don't know if that was caused by the slamming/shifting.  GM has not done any favors to themselves or their loyal customers who love the vehicles otherwise.