I am having a problem with the Hydra-Matic 6L50 six-speed automatic transmission in my 2017 Chevrolet Colorado with the Baby Duramax engine. The problem started to occur occasionally and now is increasing in frequency. I am wondering if other Colorado and Canyon diesel owners are experiencing the same thing and if there is a recall or other solution to the problem.
I first want to say that I have looked everywhere under the hood or looking at the transmission itself and I can not find a dipstick or a viewing window for measuring transmission fluid levels. There also does not appear to be anywhere under the hood for topping up transmission fluid. This is very frustrating as the problem feels like the transmission is low on fluid.
On to the problem itself... This seems to only happen when you want to go forward with the truck from a dead stop. The problem has not appeared when I am in reverse, only when the engine is in drive with the intention of moving forward. The transmission seems to become disconnected from the engine and the engine will rev freely like it is bolted to a manual transmission and you are pressing down on the clutch or are in neutral…. with the result being no forward motion of the vehicle. This can be very hazardous when you have partially rolled into an intersection and there are other drivers trying to get around you. Then, after a short period of time that can be anywhere from 1 to 20 seconds the transmission will engage with the engine very abruptly with a “thunk” sound and the vehicle jerking forward a foot or so. I try to not rev the engine when this problem occurs as it seems like the transmission achieves fluid lock-up suddenly and the result is the transmission parts get hammered.
The engine is running fine, and I am having no issues with it. This vehicle is very low mileage and only has 71,000 KM, (less than 45,000 miles), rolled up on it. I do not abuse my vehicles and this Colorado in particular has been treated very gently, so this problem where it feels like someone has burned out the transmission is very perplexing.