2014 - 2018 5.3 6 speed downshift jerks

dieselfan1 · January 23, 2021

I want to know what fluid everyone is using when they change it on the six speed?
I have two that are due.

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Grumpy Bear · January 23, 2021

16 minutes ago, dieselfan1 said:

I want to know what fluid everyone is using when they change it on the six speed?
I have two that are due.

Sent from my Pixel 3 using Tapatalk

I use Red Line D6. It's a PAO/POE blend.

Bob2C · January 23, 2021

Had my 6L80 tuned when I went with a 93 tune from Diablew. My shifts are firm going up but no jerking on the downshifts. I used to have the same problem as others with the factory tune. It was annoying. I changed out factory fill at 24k miles to AMSOIL sig trans fluid. Now have 34k miles and no issues at all. Fluid still cherry red.

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HoosierZ · January 23, 2021

1 hour ago, dieselfan1 said:

I want to know what fluid everyone is using when they change it on the six speed?
I have two that are due.

Sent from my Pixel 3 using Tapatalk

I used Valvoline Dexron VI. Menards had it for $5/qt. It’s $10/qt at all of the local parts stores.
Pump as much fluid as you can out of the dipstick tube. Way less messy that way than dropping the pan and wearing trans fluid. I added a drain to the pan while it was off.

Capt Bob · February 25, 2021

I'm doing a pan drop and filter exchange this weekend. Also using Red Line D6.

Like HoosierZ, I added a drain plug to a new GM pan.

superdave160 · February 26, 2021

The video at the link below describes the operation of the torque converter clutch with respect to current gear and whether the transmission is upshifting or downshifting. According to the video, the stock program from GM has the torque converter clutch lock up in each gear as the transmission shifts from 1st gear through 6th gear. This also occurs while the transmission is downshifting. The person in the video recommends that the program be modified so that the torque converter clutch does not lock up in gears 1-4, upshifting or downshifting. This constant locking and unlocking of the torque converter clutch while downshifting may be what you are feeling. When I saw this video, I had already installed ECM and TCM tunes from Black Bear Performance. I asked BBP about the torque converter lockup setting and Jason replied that they set the torque converter clutch to not lock in gears 1-3. I have no issues with the way that my 2017 Silverado 5.3/6 speed shifts.

https://www.youtube.com/watch?v=EHPzEG0m19w&feature=emb_rel_end

I also had the dealer perform the "tripleflush" and replace my transmission fluid with the Mobile 1 Synthetic LV ATF HP fluid as indicated in TSB 18-NA-355. The dealership initially told me that the service was covered under warrantee, but when I went to pick up the truck there was a $230.00 bill waiting for me. The technician "couldn't feel the shudder during the test drive", so it wasn't covered.

reardiff · February 28, 2021

On 2/26/2021 at 4:58 PM, superdave160 said:

I also had the dealer perform the "tripleflush" and replace my transmission fluid with the Mobile 1 Synthetic LV ATF HP fluid as indicated in TSB 18-NA-355. The dealership initially told me that the service was covered under warrantee, but when I went to pick up the truck there was a $230.00 bill waiting for me. The technician "couldn't feel the shudder during the test drive", so it wasn't covered.

As far as I know the TSB for HP fluid flush, is only for the 8 speeds. This may be the reason they denied covering it? For the 8 speeds at least, the TSB procedure for the HP fluid flush is absolutely covered under the power train warranty. I had mine done 100% covered as well as many others on this forum. The dealer saying you need to pay for it because the technician couldn't feel is not right unless it was because it is a 6 and not the 8 speed?. The TSB even states that diagnosis beyond customer complaint is not required.

Other than six speed not being part of the TSB the only other reason I can possibly see them denying it with out feeling the shudder would be if it was already done at some point and your now trying to get them to do it again.

mmmikkke · February 28, 2021

On 2/26/2021 at 5:58 PM, superdave160 said:

The video at the link below describes the operation of the torque converter clutch with respect to current gear and whether the transmission is upshifting or downshifting. According to the video, the stock program from GM has the torque converter clutch lock up in each gear as the transmission shifts from 1st gear through 6th gear. This also occurs while the transmission is downshifting. The person in the video recommends that the program be modified so that the torque converter clutch does not lock up in gears 1-4, upshifting or downshifting. This constant locking and unlocking of the torque converter clutch while downshifting may be what you are feeling. ...

https://www.youtube.com/watch?v=EHPzEG0m19w&feature=emb_rel_end

Excellent video. The solution is now known. Looks like some GM engineer chose to worship at the altar of fuel economy irregardless of the resulting shift tables making GM's customers put up with these annoying and embarrassing jerky downshifts. Don't they realize this costs them customers?? For what...an immeasurably small fuel economy improvement? It would not be the first time a rogue engineer damaged the drivability of GM vehicles to satisfy some impossible ideal.

I see now that I may have to spend the bucks to get my own Hptuners license and hardware/software.

But first I will ask hptuners that, given the niche purpose I have in mind, if they would sell a less expensive license only able to modify the tables discussed in the above video.

Thanks to superdave160 and [youtube] Richard Wardell and all who helped make the above video part of this thread.

CamGTP · March 1, 2021

The cost for the HP Tuners will be what it says on their website, nothing will change there.

It's $300 for the device and the download stuff is free on the website. Then you just need the credits for the License fee. 2014-2016's are 2 credits ($100) and 2017-2018's are 4 credits ($200). The PCM and TCM for the 6L80e are covered under that license fee. If you have an 8 speed the cost is much higher on 2017+ trucks.