I just bought me a 08 GMC Seirra crew cab with a 5.3L. My buddy tuned it with HPT and now it is constantly changing between V8 and V4 mode above 50 mph. All we did to the truck was turn off torque management, top speed limiter, shift delay, and firm up the shifts just a little bit. Has anyone else had this problem? If so what did u have to add to the tune to fix it? Thanks for any advice!

 

Go into the tune file and use the compare function
to see exactly what was changed, your recollection
of it may have overlooked something.

The torque management may be where it's at, I bet
desired torque plays into the decision about dropping
cylinders. Not every TM parameter needs to be
messed with, depending on just what you are looking
to get out of the truck. Some of it does suck, it's true,
but some of it just does a job and could be left alone
without any downside. So start rolling back the ones
that don't have directly to do with shifting (trans TM)
and traction control, back to stock and see if you can
get the DOD under control.

And go search for DOD / displacement on demand posts
here and on the HPTuners 'board, just for any more
clues.

 

Thanks a lot i'll go back over my tune and check it out A little more