New 8 speed software update?

MrNasty · July 4, 2017

Can someone resend the TSB that was seen early on on this thread. Not sure why but I can't see it.

My 2017 Denali has 1300 miles on it we were driving in a 180 mile trip. We were on the highway doing 75-80 for two hours. We slowed to exit off at our exit when the truck downshifted I actually thought I dropped the transmission. My wife said "what the hell was that". I said it was the tranmisssion downshifted. She said 6 years in the tundra and I never felt anything like that. Needless to say i think I better have it checked. When it is cold the shifting is rough as well as when moving from v4 back to v8. Hopefully the software upgrade will resolve the issues

#16-NA-411

SkiDooNick700 · July 6, 2017

Man I was driving to and from work today and except firm a little bit of a firm 1-2 shift, the rest WERE NOT EVEN NOTICEABLE!!! I'm like dang it just went thru the gears from 2-7th and didn't feel or hear a thing! Unbelievable, I am LOVING THIS!!

Hope to start seeing a lot more responses on here of people getting this done and seeing great improvement...

Dnt · July 6, 2017

Man I was driving to and from work today and except firm a little bit of a firm 1-2 shift, the rest WERE NOT EVEN NOTICEABLE!!! I'm like dang it just went thru the gears from 2-7th and didn't feel or hear a thing! Unbelievable, I am LOVING THIS!!

Hope to start seeing a lot more responses on here of people getting this done and seeing great improvement...

My issue is the harsh downshift. Did you have that and if so did this update fix it???

jlilnc14 · July 6, 2017

My issue is the harsh downshift. Did you have that and if so did this update fix it???

Yes, it fixed the hard 2 to 1 downshift when coming to a stop.

SkiDooNick700 · July 6, 2017

My issue is the harsh downshift. Did you have that and if so did this update fix it???

Come to think of it... I do not recall having a clunky shakey 2-1 downshift since I was last in for this service... so... yea!

Dnt · July 6, 2017

This is awesome I have written down the TSB number #16-NA-411

and will try to get this done (if they will) at my first oil change. I only have 2500 miles but I may just do an early oil change anyway (get that nasty factory oil out) and see if they will do this trans update . This 2017 almost identical truck to my 2016 is a LOT worse with the harsh downshift than my 2016 ever was. That is the only thing about trading up a year to an almost identical truck, you notice every little thing that is different. This bugs the chit out of me. LOL

muhsfink07 · July 14, 2017

I'm getting the fluid flush and software update on Monday finally!

quicksilver64 · July 21, 2017

I had this TSB done to my 2015 6.2 8 speed today. I was having the harsh downshift 2-1 or sometimes I think 3-1. Usually in a parking lot or traffic having to slow down abruptly. The drive back from the dealer was like i stepped into a new truck. Before I could feel the shifts on the highway although very smooth. Today the only way I could tell it was sifting was by seeing the tach needle drop.

NathanFugett · July 23, 2017

Finally got a chance to take mine back to the dealer and get it checked out. I was experiencing the harsh downshifts, clunking while at low speed shift and erratic shift ranges. Took it in and at they reprogrammed TCM and flushed the trans and refilled with new fluid . I haven't had a problem since I returned with it . Shifts are a lot smoother , hope it stays this way . I'm happy again with my truck

redwngr · July 23, 2017

Wanted a second opinion: Does this apply to the 8 speed in the 5.3L as well, I was hoping so as my truck has the same symptoms as reported here, but my dealer says it does not. I have a 2017 gmc 5.3L.

My 2016 5.3/8speed has had several updates.

The last was done late Jan / early Feb 2017.

The last one has finally corrected it.

Bhiland122 · July 24, 2017

I'm going to call dealer and request a update and service for mine. I'd love to get rid of the clunky shifts.

Joeybones · August 1, 2017

To those who whent in for the service, was it a warenty fix? I have a 2015 Chevy 1500 8 speed with all the symptoms named? Also when you mentioned the tcm number did they understand or did it take some explaining?

redwngr · August 2, 2017

To those who whent in for the service, was it a warenty fix? I have a 2015 Chevy 1500 8 speed with all the symptoms named? Also when you mentioned the tcm number did they understand or did it take some explaining?

I just told them the symptoms. They researched and found ( or already new) that updates/service instructions were available.

All have been warranty.

MrNasty · August 2, 2017

To those who whent in for the service, was it a warenty fix? I have a 2015 Chevy 1500 8 speed with all the symptoms named? Also when you mentioned the tcm number did they understand or did it take some explaining?

I took mine in for the lost coolant and delayed shift into drive. They found the TSB and did the update for me. I hadalready had stator replacement for same issue. If you look up the TSB number online and take it with you, makes it easy for them. I have printed other TSB's when I took mine in before. I had one printed for my radiator, as I had taken it in before for coolant loss and the said it pressure tested fine. When I took TSB in on radiator the second time they looked at it and found it was leaking. The more help you can give them the easieron you and less return trips for same issue.