Ben W

Thanks for the input @mymaggiebell. I might try an additive next, as it is the only other "non-invasive" thing I can think to try at the moment. Its a shame to have these kind of issues right out of the gate, especially with only 80k on the clock. I'll report my findings if the additive works.

Hi All, My first post, so I hope I'm posting in the right section. I checked a few other threads here on tranny slip issues, but none seem to line up with my issue. I recently purchased a 2011 Sierra Denali 6 speed with 79k. When driving around normally (revs under 2,500-3k), the transmission seems to shift perfectly smooth up and down. But when I get on the gas heavy, I'm noticing some slip (engine revs to about 5k before the lower gear will engage). Eventually the gear does grab, but then it will peg off redline when it should upshift also. I checked the ATF and it was low, so I did a full flush and filter. The fluid still seemed fairly clean and unburnt. I am not getting any engine codes, my trans temp always seems normal, and there are no visible leaks anywhere (at least what my untrained eye could spot) at the lines up front or the pan. After the flush, it did seem to improve somewhat, but it still exhibits the same behavior when I really get on the gas. Has anyone else experienced this, and if so, what was your findings? Any feedback is appreciated, as I am trying to get to the bottom of this before my 60 day warranty expires. Thanks in advance! -Ben