Interesting... progress with odd trans behavior? (2015 6-speed)

[Drainpipe]

('15 Sierra,CC,2wd,5.3,6sp) I tried disabling the grade brake but it made absolutely no change. I was damn hopeful that would solve or at least help this lousy transmission. In fact, I don't notice any change in coasting to a stop(?) The rpm's don't drop when coasting like I thought it would. The engine just follows the tranny downshifting until I get to around 15-25 mph then drops to idle. I do get the notification that grade brake is "off" but it doesn't change a thing.

That's strange. My '14 had a VERY noticeable difference. No searching whatsoever on gears now. I guess I was never really looking at RPMs for coasting.

 

I guess where I saw the difference is when I really step on it. I do this a lot since I got my new Borla muffler Shifts are quicker and like I said, no searching.

[No Tyme]

I guess where I saw the difference is when I really step on it. I do this a lot since I got my new Borla muffler

I have this same problem too.

[oburgtiger]

Tried this on my '14. It made a difference on downshifts coming to a stop, but the upshifts are still unpredictable and rough at times.

[wurgs]

I never really had a big problem with the way the tranny shifted after the software update so haven't noticed a big difference there but I did a little test to see if any difference in the v4 mode. There is a old US highway that is flat as a pancake and fairly straight outside of town and thought it would be a good test. The weather was mostly sunny, 83 degrees and a head wind of about 20 mph. I set the cruise at 60 mph and drove normally for 15 miles. It would go into v4 mode occasionally but wouldn't hold it. I then turned off grade braking and drove 15 more miles. The difference was very noticeable, it held v4 mode and only went out of it 3 times and then for a short time before switching back. From what I found out it will hold v4 mode way easier.

 

I started turning it off about a week ago and am checking the mileage I get to see if it makes any difference. I will wait a few months to directly compare from what I got last year at this time. I am a little anal and keep a record of all my mpgs since I bought it. I just don't know if the engine working harder in v4 mode will get better mileage than in v8 mode.

[pl8man]

Sure made a difference with mine, shifts likes it's suppose to!! Just a pain to deactivate every time.

 

[wayles]

My transmission seems to have a "Jeckel/Hyde" personality. Some days it's just fine and some days it's infuriatingly bad. Sometimes it's bad in the morning and good in the afternoon. It does seem to be a little worse if I haven't driven it for a few days but not always. There doesn't seem to be any rhyme or reason for the up and down behavior, at least nothing I have been able to identify.

 

I have been turning off the grade braking for a couple weeks now and I do notice a difference as I stated I an earlier post. However the "Jeckel/Hyde" personality still persists, it's just not as bad now.

 

One thing I found by accident is if I put the truck in tow/haul mode AND turn off the grade braking, it seems much more responsive then if I just do one or the other. I'm going to start doing this regularly and see if it helps over time. I'll let you know what I find out.

[OldBlue61]

My transmission seems to have a "Jeckel/Hyde" personality. Some days it's just fine and some days it's infuriatingly bad. Sometimes it's bad in the morning and good in the afternoon. It does seem to be a little worse if I haven't driven it for a few days but not always. There doesn't seem to be any rhyme or reason for the up and down behavior, at least nothing I have been able to identify.

 

I have been turning off the grade braking for a couple weeks now and I do notice a difference as I stated I an earlier post. However the "Jeckel/Hyde" personality still persists, it's just not as bad now.

 

One thing I found by accident is if I put the truck in tow/haul mode AND turn off the grade braking, it seems much more responsive then if I just do one or the other. I'm going to start doing this regularly and see if it helps over time. I'll let you know what I find out.

 

Would pulling the battery cable for a few hours to make the computer "relearn" your driving style help? Does that work?

[scott19677]

Look guys, these home remedies, battery disconnect, relearn driving style crap is not going to work. Its not the tow haul mode or grade braking. The problem is the factory GM programing to achieve one goal. MPG. Go get a Blackbear ECM/TCM tune and don't look back. Just saying'

[davidio840]

My transmission seems to have a "Jeckel/Hyde" personality. Some days it's just fine and some days it's infuriatingly bad. Sometimes it's bad in the morning and good in the afternoon. It does seem to be a little worse if I haven't driven it for a few days but not always. There doesn't seem to be any rhyme or reason for the up and down behavior, at least nothing I have been able to identify.

 

Mine is kinda the same way.. I have always noticed after mashing the pedal down to get through 3-4 gears and then going back to normal driving, the transmission and the truck are way more responsive after the fact.

 

When I start it up and drive normal, the transmission will sometimes search for a gear or have the 2nd-3rd gear RPM flare up occasionally. It doesn't happen all the time but the other day I was driving and stopped at a stop sign. I hit the gas and my transmission just wouldn't go into gear.. I tried manual and putting it in park and back to D and nothing. I turned the truck off and started it and boom, ran perfectly normal. I have no idea what that was about but it will be back to the dealership to see if it logged any codes for that mishap.

[wayles]

Mine is kinda the same way.. I have always noticed after mashing the pedal down to get through 3-4 gears and then going back to normal driving, the transmission and the truck are way more responsive after the fact.

 

When I start it up and drive normal, the transmission will sometimes search for a gear or have the 2nd-3rd gear RPM flare up occasionally. It doesn't happen all the time but the other day I was driving and stopped at a stop sign. I hit the gas and my transmission just wouldn't go into gear.. I tried manual and putting it in park and back to D and nothing. I turned the truck off and started it and boom, ran perfectly normal. I have no idea what that was about but it will be back to the dealership to see if it logged any codes for that mishap.

EXACTLY! Mashing the peddle and running through the gears seems to help mine also. Seems like I need to do it about every third time I drive it. This is at least a fun fix, alas a short lived one.

[andyhaug]

Look guys, these home remedies, battery disconnect, relearn driving style crap is not going to work. Its not the tow haul mode or grade braking. The problem is the factory GM programing to achieve one goal. MPG. Go get a Blackbear ECM/TCM tune and don't look back. Just saying'

Based on the claim that tuning it makes it get better MPG I would say GM failed. I really wish they would fix it, but I am coming to your same conclusion. GM is never going to look into this so tuning is the only option. I just hope I don't end up with warranty problems after tuning. Then I just need an aftermarket HMI module to fix the Pandora crashing and Bluetooth issues with the radio.

[GMCustomerService]

My transmission seems to have a "Jeckel/Hyde" personality. Some days it's just fine and some days it's infuriatingly bad. Sometimes it's bad in the morning and good in the afternoon. It does seem to be a little worse if I haven't driven it for a few days but not always. There doesn't seem to be any rhyme or reason for the up and down behavior, at least nothing I have been able to identify.

 

I have been turning off the grade braking for a couple weeks now and I do notice a difference as I stated I an earlier post. However the "Jeckel/Hyde" personality still persists, it's just not as bad now.

 

One thing I found by accident is if I put the truck in tow/haul mode AND turn off the grade braking, it seems much more responsive then if I just do one or the other. I'm going to start doing this regularly and see if it helps over time. I'll let you know what I find out.

 

 

 

Mine is kinda the same way.. I have always noticed after mashing the pedal down to get through 3-4 gears and then going back to normal driving, the transmission and the truck are way more responsive after the fact.

 

When I start it up and drive normal, the transmission will sometimes search for a gear or have the 2nd-3rd gear RPM flare up occasionally. It doesn't happen all the time but the other day I was driving and stopped at a stop sign. I hit the gas and my transmission just wouldn't go into gear.. I tried manual and putting it in park and back to D and nothing. I turned the truck off and started it and boom, ran perfectly normal. I have no idea what that was about but it will be back to the dealership to see if it logged any codes for that mishap.

 

 

EXACTLY! Mashing the peddle and running through the gears seems to help mine also. Seems like I need to do it about every third time I drive it. This is at least a fun fix, alas a short lived one.

 

Hi davidio840 and wayles,

I am sorry to hear you are experiencing some inconsistencies with your transmissions. I recognize that you are reaching out to forum members and have discovered a quick temporary fix, but if you need any additional assistance feel free to shoot me a private message.

Have a great day.

Julianne M.

GM Customer Care

[OmniGLH]

 

 

 

 

 

Hi davidio840 and wayles,

I am sorry to hear you are experiencing some inconsistencies with your transmissions. I recognize that you are reaching out to forum members and have discovered a quick temporary fix, but if you need any additional assistance feel free to shoot me a private message.

Have a great day.

Julianne M.

GM Customer Care

 

Julianne,

 

Is there any reason or explanation from GM on why so many of us here have clearly experienced MUCH better transmission behavior when disabling grade braking?

[CounterMeasure]

My '15 Denali is at the dealership for the 11th time, and they gave me a '16 SLE loaner with 6-speed that already had a few thousand miles on it. I thought all the 5.3s came with 8-speeds now, but Manual mode only goes up to 6. At any rate, it is the smoothest, most predictable transmission I've seen in any of the loaners or either transmission that's been in my truck. Maybe its the golden ticket one, I don't know, but I'd kill for that transmission to replace my 8-speed in my Denali.

[GMCustomerService]

Good morning OmniGLH,

As customer care agents we do not possess the technical expertise to speculate as to why disengaging grade breaking improves some transmissions. We rely heavily on our dealerships to be our eyes and ears in the field and they would be in the best position to provide the additional insight you are seeking. Have you brought this concern to the attention of your dealership yet? We would be more than happy to connect you. Please send us a private message if this interests you.

All the best,

Julianne M.

GM Customer Care

 

 

 

 

 

Julianne,

 

Is there any reason or explanation from GM on why so many of us here have clearly experienced MUCH better transmission behavior when disabling grade braking?