Who likes their 8 Speed?

mookdoc6 · September 28, 2017

I too say thanks for the tips. I think what Dmf10e and I would like to know is what role the flashing and such plays with the tranny shifting problems. I also find the "+ or X" part confusing. Anyway, if you could give a little more detail I think we would both be appreciative. Thanks, SB

The MASS Air Flow which is behind the + or X plastic molded support piece that is inside the cylindrical section usually used to support the Mass Sensor and for structural integrity. The flashing spill over on the edges might not seem like a big deal but it will most certainly effect your transmission and shifting behavior! Due check this component as mine which is 2016 GMC had Excessive flashing on mine too. Talk about trying to find drivability issues your never going to find?

Also Guys........If your still under warranty buy the HP-fluid for 8L90 take it to your dealer and tell them to FLUSH/FILL with 13qts new! Also put New trans filter on! Your life will change overnight!

It's honestly a damn good transmission I am impressed although the first 20,000 miles almost made me insane?

Dmf10e · September 28, 2017

The MASS Air Flow which is behind the + or X plastic molded support piece that is inside the cylindrical section usually used to support the Mass Sensor and for structural integrity. The flashing spill over on the edges might not seem like a big deal but it will most certainly effect your transmission and shifting behavior! Due check this component as mine which is 2016 GMC had Excessive flashing on mine too. Talk about trying to find drivability issues your never going to find?

Also Guys........If your still under warranty buy the HP-fluid for 8L90 take it to your dealer and tell them to FLUSH/FILL with 13qts new! Also put New trans filter on! Your life will change overnight!

It's honestly a damn good transmission I am impressed although the first 20,000 miles almost made me insane?

Is this something that works for a 6 speed as well? I understand I'm in an 8 speed forum but I'm having the same issues. Would the fluid be the same? And the dealer wouldn't have a problem putting this fluid in? I own a 2016 Silverado v6 6 speed.

mookdoc6 · September 28, 2017

Is this something that works for a 6 speed as well? I understand I'm in an 8 speed forum but I'm having the same issues. Would the fluid be the same? And the dealer wouldn't have a problem putting this fluid in? I own a 2016 Silverado v6 6 speed.

I can't comment on 6peed. They should have same exact intake and location of MASS Sensor and X or + plastic molded piece inside TUBE and you need to take a REAL GOOD LOOK AT THAT! I spent 2days screaming back and forth with different Dealership that I want a Trans flush! They were down right afraid of the 8speed other than running it for codes....which it had none and updated software etc.

I had to pull my wallet out and scream in front of all the service providers this "GUY DOES NOT WANT TO TAKE MY MONEY" Finally, had them do it and what do know my life was turned upside down and for a good thing immediately after! I don't know how GM can make the claim that the 5.3L which I have does not require the Trans flush like the 6.2 8L90's......Anyway I have the 2 bump shifts in morning cold and I have to live with it and that's Per GM once again not sure about that but it shifts NICE Now at 40K.....And I am fixing to flush it again way to much soft material floating around in these!

Malibuair · September 28, 2017

Is this referring to the bur on the actual X or + or the bur around the the outside? On mine the filter side of the x everything looks square and sharp. However there is a bur around the out side ring. Its a molded piece but on the inside it looks welded?

Edited September 28, 2017 by Malibuair

Bigmac · September 29, 2017

I’d settle for the crappy shifting if I could get the shudder on accl out of it. 2 converters and 3 flushes and still apparent from 2 nd gear on very pronounced with rv towing. Still working with gmc on fix

mookdoc6 · September 29, 2017

Is this referring to the bur on the actual X or + or the bur around the the outside? On mine the filter side of the x everything looks square and sharp. However there is a bur around the out side ring. Its a molded piece but on the inside it looks welded?

Exactly IT VERY GOOD SON! Yours looks EXCELLENT A MODEL OF PERFECTION.......I assume yours is newer 2017? Anyway that piece with the leftover slashing like mine had 1/8" maybe even 3/16" in corners created a huge problem for me and many others! Good work, nice picture....gentleman I too stroked myself when I read about and chuckled finally looked at mine around 20K and sure shit I had the problem child!

mookdoc6 · September 29, 2017

Is this referring to the bur on the actual X or + or the bur around the the outside? On mine the filter side of the x everything looks square and sharp. However there is a bur around the out side ring. Its a molded piece but on the inside it looks welded?

Everybody make sure yours looks exactly like this picture clean and sharp!

Malibuair · September 29, 2017

It's a 2016 GMC Sierra SLE 1500 Z71 with 20k on it. I guess that a good thing mine looks clean. The bad thing is I guess I still have a shifting problem. I unplugged the battery for over an hour. I did actually smooth all the casting burrs in front of the mass air flow sensor. Figured it might be causing turbulence in the air around the sensor? Frustrating problem! For the most part, I love the truck. Wish you could turn off all the electronics. Even if you turn off traction control and stabilitrack you can still feel the electronics and they it turns back on by itself over like 35mph...sounds like the 10 speed is coming soon. My buddy has a Rapture and the tranni is amazing!

Malibuair · September 29, 2017

I’d settle for the crappy shifting if I could get the shudder on accl out of it. 2 converters and 3 flushes and still apparent from 2 nd gear on very pronounced with rv towing. Still working with gmc on fix

So I just went on my first test drive from the fix above. I didn't have any burs or casting flashing but resetting the learn mode on the tranni seemed to fix my shifting problems. I drove it like a race car then back to normal then race car mode then normal. Around town and on the freeway. Maybe a 30 mile loop and it actually shifts great now!! It used to have a weird shudder, seemed to be confused what gear to be in, really hard slamming clunk into 2nd gear up hills, shifting 2 gears when it should only shift 1. I tried really hard to get it to fail and it didn't! Completely different truck!! I do have a check engine light now but, I assume it because the battery was unplugged for over an hour and it will go away. Hope this helps.

Malibuair · September 29, 2017

Is this something that works for a 6 speed as well? I understand I'm in an 8 speed forum but I'm having the same issues. Would the fluid be the same? And the dealer wouldn't have a problem putting this fluid in? I own a 2016 Silverado v6 6 speed.

Mine is 5.3, 6 speed. The tranni reset seemed to do the trick. I bought mine used with about 2k on it. Think the original babied it. I have gone about 30 miles since the reset and it shifts as you would think it should. Positive and predictable! Hope this helps.

Snoringbear · September 30, 2017

Everybody make sure yours looks exactly like this picture clean and sharp!

I don't see a pic.

Dmf10e · October 6, 2017

Thanks for the advice. I had no burs and I did the reset by undoing the battery terminals, but it doesn't seem like it fixed it. Guess I'll just have to get used to it. But it's really hard too.

CyprusTM · October 6, 2017

I have a 17 sierra. Hate it when it goes from i guess 1 to second gear it slams as if someone hit from behind. Complained to the dealership and they said its normal, don't feel normal to me. Also when idle it vibrates.

Edited October 6, 2017 by CyprusTM

Snoringbear · October 7, 2017

Having managed several clean room operations during my career as a mfg and operations mgr the comment about removing flash in the plenum so to achieve a smooth laminar flow made sense to me. But, still not understanding how this would affect tranny shifting caused me to do a little researching. Then, discovered that the high performance guys are actually drilling holes in the plenum, adding baffles, etc, so to break up smooth air flow and create improved air/fuel mix so to improve performance. Not trying to be argumentative, just sharing info. I've had three re-programs done since I bought the truck new. Also, torque converter shudder raised its ugly head at about 32K miles. Took truck to dealer and problem was confirmed. Fix was a complete tranny flush with new type HD fluid including tranny cooler (23 Qts LV fluid) and new filter. Plus tranny reprogram. This fixed the torque converter shudder problem. Btw, there's a service bulletin on this. And, the notorious low speed 2nd > 1st and 1st > 2nd hard shift is now less severe. However, the biggest improvement has been the tranny's retraining of me. When I make what was referred to way back in the day as a California Stop and only slow to about 3 ~ 5 mph I sometimes get the hard hitting shift from 2nd to 1st which I hate. But, if I come to a complete stop at the stop sign and look both ways like a good boy the tranny works fine. Sooo, I now am resigned to obeying the law and making full stops, problem solved, lol

BobHancock · October 7, 2017

Reading through this thread it seems to be a total crap shoot whether the truck tranny misbehaves or not. My 2016 Chevy with 6.2/8 got better over miles but never right. Only way to make it good was run in tow haul mode which just holds the shifts. Now my 2017 6.2/8 is perfect. No tranny shifting issues at all in noodle or sport mode. It's a mystery.

Edited October 7, 2017 by BobHancock