Who likes their 8 Speed?

tallspawn · May 15, 2016

Was unhappy with how the truck shifted until I switched off the AFM cylinder deactivation with diablosport inTune. Absolutely love the way it drives now! I firmly believe that the 8 speed tranny issues most people are having relate to the trans trying to make up for the loss of power when AFM kicks in.

I agree with this and will have mine shut off soon (BBP on the way!). Now that my exhaust is louder, I can hear when it shifts from 4 to 8 and that's the main time I notice any weirdness. I also turned off grade breaking for the first time today and it does make a difference on the low speed issue in the original post (on mine anyways).

My thinking on warranty is that both of my transmissions that have failed on me happened a little over 100k, one GM paid for half a rebuild and the other (125k miles) was all me. Both had 100k powertrain warranties. So most likely even if you have strange shifting or the "C clunk" as my service department called it on my 09 the transmission will, more often than not, last through the warranty. Even if it fails under warranty they have to prove something you did caused it, flash it to stock and take it in see if they fight it. My understanding is a well done tune can actually help the longevity of your powertrain, as long as you don't run it like a race car anyways.

Back on point, mine is a 5.3 8spd 2016, and I do like the transmission a lot more than my 09 6spd. The weird shifts are not real common for me and none have been as severe as the OP described.

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Sir Dan · May 15, 2016

Yes. I do love my 8speed now. It tows my boat way better than my 08 4speed. Always seems to be in the right gear with AFM off.

However, I'm still torn on the lack of a dipstick. I just can't get over not being able to at least check the condition of the fluid once in a while.

Edited May 15, 2016 by Sir Dan

JacobC1983 · May 15, 2016

For what it's worth, the diablo tuner I used doesn't even support the 8 speed yet. I only used it to switch OFF the afm in the ecm (engine cntl module) so no tune in the tranny.

Is there another device that can plug into the OBD port that turns off AFM? I had something similar in my Camaro ZL1... It allowed more features in the DIC as it didn't have AFM but I assume something similar would be possible for this truck. Edited May 15, 2016 by JacobC1983

Sir Dan · May 15, 2016

Yup. It's called the Range device I believe. It stays plugged in to the OBD port.

JacobC1983 · May 15, 2016

Thanks! I will check it out.

bobbobtar · May 15, 2016

Love mine after a BB tune 2016 Silverado 5.3L Went to BB at 500 miles really straightened out the transmission.

Edited May 15, 2016 by bobbobtar

FADEC · May 15, 2016

Have you taken yours in to the dealer? What have they tried to fix it?

Mine had several re-learns and a new torque converter and while it has made the problems occur less, I still get some very large clunking.

Took it in for a relearn last month. 1000 miles on it since then. No change.

JacobC1983 · May 15, 2016

That's where they started with mine as well. Two or three relearns and then a new torque converter, and a software updated to the transmission controller module. And now a field service engineer looked it over and I am waiting on his verdict. They did give me a Denali to drive as a loaner for the week though, so that's fun.

SierraMyst · May 15, 2016

Here you go:

page1.jpg

Thank you for this. My 16 just started doing this. Early mornings and after sitting in the parking got for a few hours.

I'll shift reverse, back out of my spot, and shift into drive and it'll take a couple seconds to engage drive.

As always, it doesn't do it all the time and so the dealer will tell me it can't be replicated.

Do you have any of the other pages to the TSD?

SierraMyst · May 15, 2016

New member here but a long time visitor to this site. Had to comment on my 8 speed. I have a 2016 Sierra SLT CC 4x4 5.3 and 8 speed. I have owned four GM trucks, three bought new one used.

The trans on this one is by far the harshest shifting tranny I have ever had on not only a GM vehicle but any vehicle. LOVE the truck except for the trans. Hard shifting, usually downshifting, but upshifts hard with a light throttle. By far the most annoying is when slowing down to stop right before coming to a complete stop is annoying bump/jerk feeling. Almost feels like some one ran into your rear end at slow speed. Have tried the grade braking turn off trick but no change...I think it mainly works for the 6 speed. BTW I had the same 6l80 trans in a 2009 Avalanche and it was butter smooth. I personally feel the tranny is good just the programming is very poor.

This is mine...

Straight line acceleration, no problems. Love it. Like a beast.

But the sporadic clunks down shifting while coming to a stop, the clunks from 1 to 2 to 3 while slowly driving (like a parking lot). And the shudder on v4 when driving in slow stop and go traffic from 18-25 mph drives me crazy.

And some days we're great and others I hate it.

kp52 · May 15, 2016

Thank you for this. My 16 just started doing this. Early mornings and after sitting in the parking got for a few hours.

I'll shift reverse, back out of my spot, and shift into drive and it'll take a couple seconds to engage drive.

As always, it doesn't do it all the time and so the dealer will tell me it can't be replicated.

Do you have any of the other pages to the TSD?

Its 12 pages, I have them but not in pdf and the.jpg files are large. Its pretty involved, stator support and pump cover, but any decent trans tech should be able to do it.

If you let it sit overnight at the dealer it should act up for them. Good thing is it most likely wont damage anything long term, its just annoying..

JacobC1983 · May 15, 2016

Lots of good information in this thread, thank you for the help. I feel as if I got a lemon and think I will still stick with the 6.2L and the 8 speed. The power of the 6.2L is intoxicating; especially compared to my last truck which was a 2009 Avalanche.

Edited May 15, 2016 by JacobC1983

FADEC · May 15, 2016

This is mine...

Straight line acceleration, no problems. Love it. Like a beast.

But the sporadic clunks down shifting while coming to a stop, the clunks from 1 to 2 to 3 while slowly driving (like a parking lot). And the shudder on v4 when driving in slow stop and go traffic from 18-25 mph drives me crazy.

And some days we're great and others I hate it.

Since there is only 2 votes for hating the trans and 17 for loving it. Clearly most love it and have no issues. I wonder what it actually is?? Something not assembled correctly inside?? Something going bad?? Some debris or something left inside during assembly??

Now I'm thinking it cannot be programmed wrong, as there are trucks made after mine and before mine that have no issues!!

JacobC1983 · May 15, 2016

This is mine...

Straight line acceleration, no problems. Love it. Like a beast.

But the sporadic clunks down shifting while coming to a stop, the clunks from 1 to 2 to 3 while slowly driving (like a parking lot). And the shudder on v4 when driving in slow stop and go traffic from 18-25 mph drives me crazy.

And some days we're great and others I hate it.

This my truck too.... It can be a real nightmare.

JacobC1983 · May 15, 2016

Since there is only 2 votes for hating the trans and 17 for loving it. Clearly most love it and have no issues. I wonder what it actually is?? Something not assembled correctly inside?? Something going bad?? Some debris or something left inside during assembly??

Now I'm thinking it cannot be programmed wrong, as there are trucks made after mine and before mine that have no issues!!

At least this thread makes me think we are a minority of people. I hope my next one puts me in the "good" camp.