My 2016 GMC Sierra SLT with the 8L90 transmission has troublesome that started sometime after about a year after owning this truck brand new. The problem exists primarily in lower gear shifts where at times it feels like someone hit the rear end of my truck when all it did was shift a gear. My wife who witnessed this the first time asked me "what the hell was that"? Slip, buck, kick, jerk, and harshly engage are the symptoms I experience. I did bring the truck in a couple times to the dealership when it was still under warranty who did at one time did a "power flush" of the transmission fluid which did help for awhile - maybe a month before all the shifting issues returned. I was told the other time "we could not duplicate the problem and there are no codes". On occasion while going 40 to 50 mph the RPM's will race up about 800 RPM's and then return to what the normal should be. This happens when I'm just cruising along at a steady speed. I just recently had the transmission temperature sensor cable replaced by the dealership which kept throwing a P0700 and P0711 code.
8 speed transmission would bump (shutter) at very low speeds like searching for gear between 2 & 10 MPH.
1st trip to dealer flushed transmission (did not work)
2nd trip to dealer replaced valve body in trans and fluid (did not work)
3rd trip denied claim to replace transmission, stated this is normal and will not damage transmission. I left GMC Sierra at dealership since I had new loaner truck from dealership. I called GMC consumer hotline and explained concern. Took another 5-days and they approved transmission replacement at 47K miles under powertrain warranty (no charge)
So far 2,000 miles on new transmission and no issues.
Their fix did not fix the problem, if anything it is worst now. It also lurches when coming to a stop, when shifting gears it shifts rough and jerks. this is the second time the transmission has been recharacterized for the same problem and it is still not fixed.
Purchased a CPO 2016 Sierra Denali with the 6.2L engine and only 20K miles in June. About a week after purchasing, I notice the vehicle was shifting weird...mostly at slow speed and a few times at higher speeds. Went to the dealership to get the truck looked at and was told nothing is wrong...it shifts as it should. I drive off to head back home and the same issues were present. A few weeks later, I take it back for the same issues as described previously. After having the vehicle for 5 days, they tell me I have a bad valve body which needs to be replaced, but the part is on back order and will not be available until sometime in September which is about a 3 to 6 week wait. This is unsatisfactory for a nearly new 60K+ vehicle to be having this sort of issue. Hopefully, this fixes my truck.
Rough shifting, especially 1st to 2nd. Its like popping the clutch on an manual transmission. It feels like the transmission is in neutral and finally engages and bumps the truck. At times it seems like it is in a gear that is too high for a given speed and " lunks " for lack of a better term. Also does a little bump on down-shift from 2nd to 1st also. Dealer solution is to reprogram transmission -never works!
A D V E R T I S E M E N T S
My 2016 GMC Sierra SLT with the 8L90 transmission has troublesome that started sometime after about a year after owning this truck brand new. The problem exists primarily in lower gear shifts where at times it feels like someone hit the rear end of my truck when all it did was shift a gear. My wife who witnessed this the first time asked me "what the hell was that"? Slip, buck, kick, jerk, and harshly engage are the symptoms I experience. I did bring the truck in a couple times to the dealership when it was still under warranty who did at one time did a "power flush" of the transmission fluid which did help for awhile - maybe a month before all the shifting issues returned. I was told the other time "we could not duplicate the problem and there are no codes". On occasion while going 40 to 50 mph the RPM's will race up about 800 RPM's and then return to what the normal should be. This happens when I'm just cruising along at a steady speed. I just recently had the transmission temperature sensor cable replaced by the dealership which kept throwing a P0700 and P0711 code.
- rutabeggerslt, Roselle, US