Transmission issue, but only when cold

[Eric J]

Finally found a dealership that would do anything,  4 cases with gm opened and closed . They just did the triple flush and relearn almost 200 miles ago and  it did nothing.  The only way to fix this seems to be to file a lemon law,  GM reps put in for a buy back, they keep saying they haven't got a response back that was before Christmas!! I now have just about 5k miles and this will be the last GM vheicle I will ever own..... GM is total trash and a class action suite needs to be brought againt them . Never ever again will I support GM  .My 2 young kids notice when its acting stupid they now say that GM is junk and everytime  it acts up my 7 year old says dad I'll never buy a GM when I grow up... 

Edited January 22, 2019 by Eric J

[Ohiozr2]

8 minutes ago, Eric J said:

Finally found a dealership that would do anything,  4 cases with gm opened and closed . They just did the triple flush and relearn almost 200 miles ago and  it did nothing.  The only way to fix this seems to be to file a lemon law,  GM reps put in for a buy back, they keep saying they haven't got a response back that was before Christmas!! I now have just about 5k miles and this will be the last GM vheicle I will ever own..... GM is total trash and a class action suite needs to be brought againt them . Never ever again will I support GM  .My 2 young kids notice when its acting stupid they now say that GM is junk and everytime  it acts up my 7 year old says dad I'll never buy a GM when I grow up... 

Mine has 50k miles, but it will “pause” when shifting from second to third after sitting overnight.

[Eric J]

Ok so the problem has gotten even worse even after warmed completely up the hesitation is bad.Trying to maintain  55 was bad had to either do 52 or 60 mph. The transmission snap is still there when shifting into 3rd . The transmission fluid flush did nothing even 2k miles later. Opened case with ohio attorney general's office and GM sent them false documents saying I didn't have duplication but the attorney general's office had the paperwork in hand. And now have started a lemon law last week.....

Edited April 21, 2019 by Eric J

[Slash L86]

On 1/21/2019 at 5:53 PM, Ohiozr2 said:

Mine has 50k miles, but it will “pause” when shifting from second to third after sitting overnight.

I also get the pause when cold effect. I live in Vegas where it's usually not even that cold in the mornings. Did it a few times last year and already a few times this year. Just had the flush done. Gonna give it a few days to see if it goes away. If still present I'll bring it in and ask about updates, etc...

I believe my random shutter is cured though. Least I didn't notice it on my last 150 mile round trip I took.

2018 silverado 1500 6.2 4x4 nht 6,800 miles

[Slash L86]

On 10/24/2018 at 1:03 PM, Doublebase said:

Something else to consider that I never even thought of until now, this fish bite sensation when the engine is cold may not necessarily be the transmission. It could be the engine. 

 

Direct injection engines suffer from preignition and engine knock when it's cold. The knock sensors could be peeling back on the timing, causing the jerky, sort of fish biting sensation. Then it warms up and goes away. 

 

But like ive said before, I've been experiencing this since my truck was new back in April (2018 Silverado 5.3). I now have 16,000 miles...no change for better or worse. The thing is driving excellent aside from this cold start issue. 

 

I think this may be causing the pause effect. Just doesn't make sense for the trans not to properly grab a gear the way it's acting.

[Doublebase]

3 hours ago, Slash L86 said:

I think this may be causing the pause effect. Just doesn't make sense for the trans not to properly grab a gear the way it's acting.

Yeah and mine still does it, I'm at 42,000 miles now. No change, no big deal I guess.

[MakeMyGM]

I get the same "fish Bite" only when cold. (5.3 6sp tran). Goes away usually within .5 to 1 mile (in Florida where temp are a lot warmer then north)

My dealer tech rep told me, that the transmission has a thermostat in it, and until it warm up will cause that issue.

 

If they know the issue, why cant they just replace the thermostat, if replaceable. I know for instance some transmissions on some vehicles are so complicated that the manufacture will not allow the dealer service techs even open up a tranny.

 

These stupid things they put into vehicles cost us more, create issues, all for a sill "presumed savings" in fuel. IE Auto Stop Start, V8-V4 crap.

[Erb2017]

I would like to share my knowledge and hope it might help some of you. I used to be a transmission mechanic back in the 90's. I bought a used 2017 Silverado 5.3 6l80 LT with 36k miles back in May 2020. I too noticed that while warming up that the transmission would shutter, sometimes hunt gears etc. These transmissions are a clutch to clutch type which means that torque management must be used in order for the gear changes to complete, release of 1 set of clutches, then apply of next clutches(Gear engagement). I replaced the fluid and filter with Valvoline synthetic Dex VI, 12 quarts which is what these transmissions hold total. I also did the thermostat mod to the inline transmission cooler line which allows trans fluid to flow continuously because I have read where these thermostats fail causing overheating of the trans 230F+ which caused piston seals failure etc. burning up frictions and steels. The fresh syn fluid really smoothed out the trans shifts but I still had something glitching the trans while warming up and normal temp driving. I purchased HP tuners interface, downloaded the free software, bought 4 credits to unlock my 17' Silverado and began to study online. I did some logging of the truck and noticed that torque management on the engine side was engaging a lot above 1500 rpms meaning the engine was capable of producing gobs of torque down low but TM was pulling throttle and timing causing the little hiccups along with AFM/DOD 4 cyl mode making it much worse. I eventually decided to play with those settings to see what happens. I disabled AFM/DOD, then I added  10% in the peak torque tables above 1500 rpm and 20% above 2000 rpm and my truck became the smoothest running, shifting beast that I have ever driven. I kid you not, I logged making 350 lb ft torque at or below 2000 rpm. My neighbor has 2016 Silverado 5.3 with the nightmarish 8 speed trans and was driving him insane with all the clunking. After talking with him with what I had done, he decided to pay me to unlock his truck and try the same tuning with new fluid and filter change since he was more than due at 72k miles. His truck now shifts perfectly and is smooth as butter with more power and better driveability. He is totally happy with his truck now too! So I truly believe that the engine torque management pulling throttle and timing is what we all are feeling because these engines make a sh*t load of torque down low in rpm range. Getting those tables up some above 1500 rpm let the engine make the power without interruptions. Now mind you the TM on the transmission TCM must remain in order for the shifts to happen correctly and I have not had to touch the trans tune at all except I did disable the TCC lockup in 1st thru 3rd gear to stop the lockup madness when going between traffic lights in town. I truly hope this helps someone. 

Edited December 9, 2020 by Erb2017

[1968starcraft]

I also have the Chevy 2019 new style pick up truck 4x4 (without 4 wheel drive low/high option) and when cold  sometimes no  forward or reverse works at all. I had it back to the dealer and they could not replicate issue. This is scary because for 50 years I could start a chevy pick up truck put it in gear and go. This is also a safety because you can put in gear and push on the gas pedal and all of a sudden it hard shifts into gear and lunges forward or backward.

[Fixxer]

A small update to this to think about: As an experiment, I tried using the tow/haul mode one morning while going to work. No bad behaviors from the trans at all. Of course the shift points were higher, but no cold shuttering. Makes me think that the shift programming is what's causing the weird cold shifting, and not an actual mechanical problem in the trans itself. What say you all?

[flyingfool]

All you guys can save a lot of time and trouble if you would just take the truck to a professional tuner and void the warrante. Just ask to have the trans tuned for reliabilty not racing. you'll be back on the road and happy with correct shifts and cool running transmission. the factory transmission map is horrible and will barely get you to 100K miles before tear down

Edited December 22, 2020 by flyingfool

[flyingfool]

On 12/8/2020 at 7:16 AM, Erb2017 said:

I would like to share my knowledge and hope it might help some of you. I used to be a transmission mechanic back in the 90's. I bought a used 2017 Silverado 5.3 6l80 LT with 36k miles back in May 2020. I too noticed that while warming up that the transmission would shutter, sometimes hunt gears etc. These transmissions are a clutch to clutch type which means that torque management must be used in order for the gear changes to complete, release of 1 set of clutches, then apply of next clutches(Gear engagement). I replaced the fluid and filter with Valvoline synthetic Dex VI, 12 quarts which is what these transmissions hold total. I also did the thermostat mod to the inline transmission cooler line which allows trans fluid to flow continuously because I have read where these thermostats fail causing overheating of the trans 230F+ which caused piston seals failure etc. burning up frictions and steels. The fresh syn fluid really smoothed out the trans shifts but I still had something glitching the trans while warming up and normal temp driving. I purchased HP tuners interface, downloaded the free software, bought 4 credits to unlock my 17' Silverado and began to study online. I did some logging of the truck and noticed that torque management on the engine side was engaging a lot above 1500 rpms meaning the engine was capable of producing gobs of torque down low but TM was pulling throttle and timing causing the little hiccups along with AFM/DOD 4 cyl mode making it much worse. I eventually decided to play with those settings to see what happens. I disabled AFM/DOD, then I added  10% in the peak torque tables above 1500 rpm and 20% above 2000 rpm and my truck became the smoothest running, shifting beast that I have ever driven. I kid you not, I logged making 350 lb ft torque at or below 2000 rpm. My neighbor has 2016 Silverado 5.3 with the nightmarish 8 speed trans and was driving him insane with all the clunking. After talking with him with what I had done, he decided to pay me to unlock his truck and try the same tuning with new fluid and filter change since he was more than due at 72k miles. His truck now shifts perfectly and is smooth as butter with more power and better driveability. He is totally happy with his truck now too! So I truly believe that the engine torque management pulling throttle and timing is what we all are feeling because these engines make a sh*t load of torque down low in rpm range. Getting those tables up some above 1500 rpm let the engine make the power without interruptions. Now mind you the TM on the transmission TCM must remain in order for the shifts to happen correctly and I have not had to touch the trans tune at all except I did disable the TCC lockup in 1st thru 3rd gear to stop the lockup madness when going between traffic lights in town. I truly hope this helps someone. 

did you do the Fast Learn procedure while in HPT? it should clean up the shifts. try do it every oil change as part of maintnance

Edited December 22, 2020 by flyingfool

[flyingfool]

5 hours ago, Fixxer said:

A small update to this to think about: As an experiment, I tried using the tow/haul mode one morning while going to work. No bad behaviors from the trans at all. Of course the shift points were higher, but no cold shuttering. Makes me think that the shift programming is what's causing the weird cold shifting, and not an actual mechanical problem in the trans itself. What say you all?

thats because Tow Haul reduces the TCC lock up if not completely disables it

this is th main issue with GM's trans tun, they lock the TCC in every gear. 1-6th. causes heavy wear on the clutch and your guys who never popped the t-stat out are frying your TCC clutch as the torque converter is atleast 100 degrees hotter than displayed on the Trans temp gauge

[Erb2017]

No need to Fast learn, I listed in my previous post what problems was causing the hiccups when I logged using HP while driving and my solutions. Torque management on the ECM(Engine) is what I was feeling, I could see TM pulling timing and throttle to keep torque demand tables at their listed torque numbers even though the engine can produce more than original GM programming. You have a lot of perimeters that add timing when cold such as IAT (Intake air temp sensor) that adds timing when cold, so with cooler denser air even more torque can be made causing the pauses of TM pulling timing and throttle. I raised these TM tables by 10% above 1500 rpm and 20% above 2000 rpm which smoothed the 3D graph and torque table making for much smoother acceleration without TM trying to hinder the engine making power. I also failed to mention that I zeroed the IAT table below 126 F because that too creates timing and throttle change pulls. Also disabling AFM/DOD helps tremendously because the ECM uses different TM tables, timing etc which causes even more delay. TM on the TCM side is set at 1.0 shift timing which is your shift speed. I do not recommend changing this to anything lower for these transmissions need that time to shift properly and smoothly. Changing to a better synthetic fluid and adding black bottle lubeguard friction modifier will aid the TCC to engage smoothly without shudder. 

[flyingfool]

2 hours ago, Erb2017 said:

No need to Fast learn, I listed in my previous post what problems was causing the hiccups when I logged using HP while driving and my solutions. Torque management on the ECM(Engine) is what I was feeling, I could see TM pulling timing and throttle to keep torque demand tables at their listed torque numbers even though the engine can produce more than original GM programming. You have a lot of perimeters that add timing when cold such as IAT (Intake air temp sensor) that adds timing when cold, so with cooler denser air even more torque can be made causing the pauses of TM pulling timing and throttle. I raised these TM tables by 10% above 1500 rpm and 20% above 2000 rpm which smoothed the 3D graph and torque table making for much smoother acceleration without TM trying to hinder the engine making power. I also failed to mention that I zeroed the IAT table below 126 F because that too creates timing and throttle change pulls. Also disabling AFM/DOD helps tremendously because the ECM uses different TM tables, timing etc which causes even more delay. TM on the TCM side is set at 1.0 shift timing which is your shift speed. I do not recommend changing this to anything lower for these transmissions need that time to shift properly and smoothly. Changing to a better synthetic fluid and adding black bottle lubeguard friction modifier will aid the TCC to engage smoothly without shudder. 

i will dig into some of the TM this weekend.. but first step in shutting off TCC 1-4th gear. i'm still understanding the software and where everything is located.  got a link to any of your suggested research vids on youtube?

 

i'm trying to figure out how to limit the amount of gear kickdown(passing gear) on the 6l80. there been times i was in Drive, stomped the pedal and i swear I'm in 2nd gear from 6th. crazy stuff.