6 Speed vs 8 Speed Reliability

[1SLOW1500]

A tune? Will I be able to keep my AFM if I get a tune? I'm already averaging 24.5, a tune would help me get better than that? I'm interested. Is this something that would void my power train warranty? If so I'll probably wait till I'm out of warranty.
 
Regarding the pan drop/filter/fluid change...it honestly has seemed to help...I haven't had the shutter going up the hill on the highway that it started doing it on. But I'm not holding my breath, I've never really seen a tranny fluid change do much of anything in regards to driveability, so if the shutter returns I won't be surprised. 

You can keep afm but you don't want to. Once the shifts and line pressure are smoother it is best to disable afm. The customer tune can have a few trans tune. Normal,tow,manual,ect..... power enrichment is reducing most all the power,with this reduced or removed the shift command and wear on trans is easier. Also power made is used more efficiently. Rather then slipping trans to bleed off power.
If you own the tune device you can just flash truck to stock when you take truck in for service. A tune does not directly void a warranty. It must be proven the exact cause in tune that caused the issue. And only the service claim is not covered. Not whole warrant forever.

Sent from my SM-N960U using Tapatalk

[3tspapat]

What kind of driving do you do that you average 24.5 mpg? 

[2016 Sierra Owner]

I would stick with the 6 speed. I had one in my 14 and 16. I never had any issues with them. Every once in a blue moon did it try to gear hunt.

[2018GMC]

8L90 has been good to me but only has 9500 miles on it. No weird shifting. Still has the original hygroscopic fluid but i don't have any rpm fluctuation on highway or shudder. Will most likely get it flushed with the new fluid at 30k miles.

 

Only oddity is it will sometime lurch forward on cold starts in park. I've towed 4k lbs across the desert (105 degrees outside) for hundreds of miles and temps were 185 - 205 with stock thermostat. 

 

I have a range device i use around town to keep it in V8. That really cleans up the shifting. On highway trips i use V4.

 

6.2L max tow 3:42 gear 8 speed 33" BFG KO2 Crew 6.6' standard bed.

[Hashtagthis]

On 11/21/2019 at 3:42 AM, 1SLOW1500 said:

You can keep afm but you don't want to. Once the shifts and line pressure are smoother it is best to disable afm. The customer tune can have a few trans tune. Normal,tow,manual,ect..... power enrichment is reducing most all the power,with this reduced or removed the shift command and wear on trans is easier. Also power made is used more efficiently. Rather then slipping trans to bleed off power.
If you own the tune device you can just flash truck to stock when you take truck in for service. A tune does not directly void a warranty. It must be proven the exact cause in tune that caused the issue. And only the service claim is not covered. Not whole warrant forever.

Sent from my SM-N960U using Tapatalk
 

The new trans fluid does not attract moisture so it is better. Nobody has figured out a way to crack the 8 speed tranny to tune. GM locked this one down and nobody has figured out how to do anything with it. I dont even think the custom tune guys are doing shift firmness or shift points yet. But you cant buy one off the shelf. 

[1SLOW1500]

The new trans fluid does not attract moisture so it is better. Nobody has figured out a way to crack the 8 speed tranny to tune. GM locked this one down and nobody has figured out how to do anything with it. I dont even think the custom tune guys are doing shift firmness or shift points yet. But you cant buy one off the shelf. 

The 8speed tcm for the 16,17,18,19 are unlockable and tuned all the time. No issues to them. Also I got a email saying the newest trucks are also available or will be any minute. I agree on the new fluid but think how many don't have that fuild. Also there are issue in both trans with the slip causing wear. This is why anyone that tunes knows once you start making good power on these trans tune is needed. 6 months or so ago i would say there isn't a great understanding on how to tune the trans. But things are much better now.

Sent from my SM-N960U using Tapatalk

[Doublebase]

On 11/21/2019 at 8:37 PM, 3tspapat said:

What kind of driving do you do that you average 24.5 mpg? 

Honestly, I get asked this all of the time because my friends and I all drive 2014-2018 Silverado's and the closest one to me is averaging around 20. My commute is 80 miles round trip everyday...most of that is highway (cruise set at 68) and the rest is country back roads driving at 40mph. Very rarely am I "into" the pedal. The truck seems to be able to glide along without much throttle input. Not sure if I'm being helped a lot by the stock 17 inch tires/rims (my friends all have 18's or larger), so that's probably helping a bit too.

[Doublebase]

On 11/21/2019 at 6:42 AM, 1SLOW1500 said:

You can keep afm but you don't want to. Once the shifts and line pressure are smoother it is best to disable afm. The customer tune can have a few trans tune. Normal,tow,manual,ect..... power enrichment is reducing most all the power,with this reduced or removed the shift command and wear on trans is easier. Also power made is used more efficiently. Rather then slipping trans to bleed off power.
If you own the tune device you can just flash truck to stock when you take truck in for service. A tune does not directly void a warranty. It must be proven the exact cause in tune that caused the issue. And only the service claim is not covered. Not whole warrant forever.

Sent from my SM-N960U using Tapatalk
 

Thanks for the info.

 

I ended up doing a pan drop, filter replace and new fluid last week and it's been 700 miles since...the shutter I was getting on the highway is gone. I'm stunned. Never before have I had something "fixed" by doing a transmission service...not sure I'm out of the woods yet, but it is encouraging. My truck only has 41,000 miles.

[1SLOW1500]

Thanks for the info.
 
I ended up doing a pan drop, filter replace and new fluid last week and it's been 700 miles since...the shutter I was getting on the highway is gone. I'm stunned. Never before have I had something "fixed" by doing a transmission service...not sure I'm out of the woods yet, but it is encouraging. My truck only has 41,000 miles.

Reset the trans adaptive tables and it will really amaze you. Then all you need to do is keep eye on temp 180ish and you are perfect. Over 200 fluid life is reduced.

Sent from my SM-N960U using Tapatalk

[Doublebase]

16 hours ago, 1SLOW1500 said:

Reset the trans adaptive tables and it will really amaze you. Then all you need to do is keep eye on temp 180ish and you are perfect. Over 200 fluid life is reduced.

Sent from my SM-N960U using Tapatalk
 

Disconnect battery? 

 

As far as transmission temps; over the life of the vehicle I probably only got the thing over 200 twice...once was climbing an auto road up a mountain, the other was during a 3 hour drive through a heat wave. Other than that the transmission pretty much lives in 140-180 temp range (it's cold around here 6 months out of the year). I think I pretty much have all the fluid replaced/refreshed...I did a drain and fill at 20,000 miles through the dipstick tube, and then the pan drop at 41,000 miles. I think I'll just plan on doing drain and fills once a year until I decide to drop that pan again (could be a few years).  

[mike d johnson]

On ‎11‎/‎17‎/‎2019 at 7:06 PM, SilveradoCustom said:

Hi all,

 

I'm considering a Silverado Custom, 5.3L 4x4. I don't need anything fancy, just something to pull my 4500 lb boat during the summer without any issues.

 

I'm trying to figure out how reliable the 6 speed auto is in the Custom trim with the 5.3L. It looks like it craps out between 120-150k regardless of maintenance and use. 

 

I really would rather stay away from the 8 speed at all costs, which is why i am looking at the 6 speed.

 

What's your thoughts on this transmission? Good, or should I be worried, especially since I'll be buying used?

Thanks for any input.

stay away from 8 speed

[L86 All Terrain]

My sixtwo killed a 8L90e in 10,000 miles after it received a second torque converter, so I was on Trans#2 in 15,000mi. All is well for another 15,000mi since.

 

I hated the 6 speed in my 2010 5.3L as it would gear hunt and downshift harshly at random. Now the 6L80 in my 2014 5.3L will lock itself into 2nd gear while decelerating/coasting into 35mph zones and wont shift out of second without a OBD computer to reset the CEL. This problem is AFM related as it only does it when decelerating between 40 and 35mph when AFM kicks in. GM has swapped the TEHCM twice and it hasn't cured it, but if driven in M5 (no AFM) the trans wont try to commit suicide.

 

In my humble opinion, both transmissions are dogsh!t. Hopefully this 10 speed fixes things when we are all forced to buy a new truck within 6-8 years.  

[SilveradoCustom]

I talked to the contractor who worked on my house yesterday.

 

09 Silverado, 5.3 w/ 6-speed.

 

He has 170k on it. Factory engine and trans. Most of those miles are towing an enclosed trailer full of tools. Truck also has a ladder rack and a toolbox in the bed.

 

No AFM delete, no catch can. Said he replaced alternator, TB, and an oil sensor. That's it.

 

I'm sold.

[SilveradoCustom]

8 minutes ago, L86 All Terrain said:

My sixtwo killed a 8L90e in 10,000 miles after it received a second torque converter, so I was on Trans#2 in 15,000mi. All is well for another 15,000mi since.

 

I hated the 6 speed in my 2010 5.3L as it would gear hunt and downshift harshly at random. Now the 6L80 in my 2014 5.3L will lock itself into 2nd gear while decelerating/coasting into 35mph zones and wont shift out of second without a OBD computer to reset the CEL. This problem is AFM related as it only does it when decelerating between 40 and 35mph when AFM kicks in. GM has swapped the TEHCM twice and it hasn't cured it, but if driven in M5 (no AFM) the trans wont try to commit suicide.

 

In my humble opinion, both transmissions are dogsh!t. Hopefully this 10 speed fixes things when we are all forced to buy a new truck within 6-8 years.  

The 6 speed problems sound almost entirely tune related. The 8 speed is mechanical.

 

I'll take something that can be solved with a mild tune versus torque converter and trans grenades any day of the week.

[L86 All Terrain]

24 minutes ago, SilveradoCustom said:

The 6 speed problems sound almost entirely tune related. The 8 speed is mechanical.

 

I'll take something that can be solved with a mild tune versus torque converter and trans grenades any day of the week.

For what its worth now that my 8L90e is operating as designed, I would not trade it for a 6L80e. It's smooth every day now whereas both 6L80e's I had were rough. Could be mostly tune related but we should not have to tune our transmissions to make them work properly. I wanted the 4L60e when I bought my 2010, but the SLT trim pushed me into a 6speed. The 6L80e has had a lot more time to have its programing ironed out and they still cant do it so I have little faith in GM transmissions these days. Where GM was admired for their auto transmissions by Ford and Ram owners ten years ago, they seem to be the worst in the pack now.