2015 GMC sierra 1500 transmission

yosoy1an2.O · April 21, 2023

my truck sometimes when it shifts from 1st gear to 2nd , it shifts hard. Only on those gears after that, it shifts just fine. My question is , if i replace the transmission oil will fix the problem? or eventually my tranny will break? it only has 67k is a 6 speeds.

also a really long time ago i search about this issue. someone said the on a comment that the factory fluid that those truck were made, was not good and it was causing the gears to shift hard. The fluid had to be replace with a new transmission formula that they made to fix this issue. If it is true , which transmission fluid should i buy?

thanks

CamGTP · April 21, 2023

The fluid stuff is for a 8 speeds, not a 6 speeds.

Only use Dexron6 fluids for the 6 speed. If you have access to a nicer scan tool I would do a reset/relearn of the transmission adapts and see how it performs after that.

Grumpy Bear · April 21, 2023

When they sit a few hours sometimes, they get a bit of air in the valve body. Bump the 1-2 change then fine after that. End plugs on the shuttles don't always seal really well. Having said that, if you haven't changed fluid by 67K you're overdue.

rav3 · April 21, 2023

I 2nd grumpy. I'd do a drain & fill using Dexron 6. As Cam said, the other transmission fluid was for 8 speed. Also a good time to change transfer case oil if u have a 4x4 and also both differentials,IMO. I also had a bottle of Lubegard to Trans to slicken seals up. Again, just my choice.

Oh yeah, u might want to do the 'pill flip' to keep transmission fluid cooler.