When i put tow mode on its a lot less noticeable.. I barely notice any fluctuation like in the video ... Ive since turned off DOD and it doesnt do it with the DOD off. I have my new ECM and have a time set at dealer for monday mornin to flash/reflash it. Will see from there.

By lock up are you referring to torque converter? That was athought as well because it will shutter through the drivetrain if you dont lift offf gas or mash on it to get harder acceleration
Thanks for the input ..As always any help Is always welcome.

 

Thats what the boards are all about

Sounds like there is a communication problem with the lock up controls somewhere. Id check VSS feeds and the grounds. In fact I usually start by simply adding some ground wires to the components Im having issues with as it never hurts and a lot of times fixes the issue. Anyways at least your narrowing it down now.

 

VSS --- as in Vehicle Speed Sensor? Where would it be located? Will look into that as well as the grounds .. I had chkd all grounds before but will dble chk again .. Thanks

 

Theres three. One on each front wheel and one on the trans. The front ones corrode and it messes up the resistance values which may be playing a role here. Id also get a good look at the wiring involved with the tow/haul button and all supporting aspects ( hence why I suggested VSS feeds ) Im pretty sure the speedo only runs off trans VSS but the lock up might reference the wheel vss as well. Not 100% on that one, your going to have to dig up some schems and sort through it. But id definitely start by adding some grounds and a good visual on the tow/haul wiring and the tune itself may be messed up. These little gremlins can spiral into a lot of effort, quick. I really wish I didnt know that first hand either. Anyways best of it

 

My 2000 5.3 does this too. It gets quite annoying.

 

Now im hoping its the torque converter lol at least i kno that i can find and fix that! Thanks for the info... I will start getting into these other issues as soon as get the new ECM flashes Monday

 

The oscillating up n down? Oh yes annoying with DOD off its not doing it as far as i can tell but havent really driven it far .. Been taking the ol ladys infinti to work until i get the ECM done Monday

 

Update to that post^^^^ Its still doing what the video shows stock tune with DOD off but no shutter in the drivetrain ... Put tow mode on and it doesnt do it ...

 

Cannot locate the trans speed sensor ... ive looked at gm diagrams of the 2010 6l80e online and where they show it is located it isnt there(passenger side tail section area)... i had went purchase the one listed on gm website from local parts place and never really looked ...but when i look at diagram for 2010 6.2 6l90e diagram there isnt one there which looks just like my 6l80e...mine is from 2010 sierra and wasnt a 6l90e....back to square one on that one... never looked for the front ones yet figured i would check one at a time...

 

Rear speed sensor (VSS) is not in trans tailshaft on 4wd models; it's in the rear of the transfer case (top side). Good luck, hope you get this sorted out!