Trifecta Tune? 2017 Sierra 6.2L 8sp Trans

wlezel · March 19, 2021

Hey guys,

So I've had my truck for a little over 3 years and it's been nothing but a nightmare with this POS transmission. I went the Diablosport i3 handheld and even custom Lew ECM tune not long after owning the truck and that didn't go well at all, actually made my tranny more clunky for whatever reason (mainly downshifts got worse over stock tuning). I ended up selling the Diablosport and picking up a Range AFM delete device which has served me well. Lew was awesome by the way and very responsive to emails, it's just the ECM tune alone did nothing for me since the Tranny was so bad, and actually made things worse in some respects.

My tranny got the awful shudder 3 months ago, and the dealer flushed it with the new TSB fluid which fixed the shudder. It drove overall GREAT for a few weeks (because they reset the TCM memory). However, it's back to complete ****** again. Delayed engagement (worst part), clunky downshift around 20mph, lurching etc...

MY QUESTION: Has anyone tried the Trifecta tune on their crappy 8 speed? To my understanding, Trifecta and HPTuners are the only folks who can tune this trans. I'd LOVE to hear some current/recent feedback from anyone on this before I drop $500. At this point, I almost want to get rid of the damn truck, but as a last resort I'm willing to try the tune before dropping some money on a new vehicle due to GM's incompetence

Thanks guys!

Edited March 19, 2021 by wlezel

Chad2815 · March 20, 2021

Flush with Amsoil ATF, worked wonders for mine. Still get the clunk on the initial start and takeoff but it the clunks have been 90 percent eliminated.

JimCost2014 · March 20, 2021

On 3/19/2021 at 7:27 AM, wlezel said:

I almost want to get rid of the damn truck

No point in driving something you do not like, life is too short to be in a bad mood every morning when you start driving the truck.

Edited March 20, 2021 by JimCost2014

NWI Denali · March 20, 2021

3 hours ago, Chad2815 said:

Flush with Amsoil ATF, worked wonders for mine. Still get the clunk on the initial start and takeoff but it the clunks have been 90 percent eliminated.

Is the amsoil GM spec? Cuz didn't mobil 1 make a new atf specifically for the 8L90?

Chad2815 · March 20, 2021

I have no idea....Black02Silverado could probably answer the spec stuff better. What I do know is my 8 speed had been flushed 3 times with the “new” mobil 1 stuff and all of its bad manners returned after about 3 thousand miles each time.I finally found a dealer that was useful and they did a quick re learn and then I had the fluids swapped and it worked for me. Before doing this it was embarrassing to have passengers because it sounded like the transmission fell out every time I slowed down to a stop.

jvbronco · March 20, 2021

38 minutes ago, Chad2815 said:

I have no idea....Black02Silverado could probably answer the spec stuff better. What I do know is my 8 speed had been flushed 3 times with the “new” mobil 1 stuff and all of its bad manners returned after about 3 thousand miles each time.I finally found a dealer that was useful and they did a quick re learn and then I had the fluids swapped and it worked for me. Before doing this it was embarrassing to have passengers because it sounded like the transmission fell out every time I slowed down to a stop.

What did you ask for... what was the catalyst for the last dealer to do a re learn? My truck is in the shop now having a temp sensor replaced and getting the new fluid.

wlezel · March 20, 2021

Can anyone vouch for the Trifecta tune for the 8 speed? It would be worth it to me if it makes the driving experience better. Sure beats buying a new truck.

The newest fluid change TSB definitely fixed my shudder issue but the delayed engagement when doing a rolling stop then hitting gas is awful, as well as the clunks.