Diablosport Forums

Have a 2012 5.3L 6 speed GMC Sierra 4x4.

So Im at a loss to whats causing very hard shifting at partial to wide open throttle. I did the trans firm shift tune, and turned off torque management at the same time. Truck shifted VERY hard at WOT and somewhat harder at partial throttle. I drive pretty hard so this isnt good.

Googled a bit and found people saying the same thing, turned down firmness to -5 for partial shift and -3 for WOT for normal shifting. It helped, but at WOT its still a bit much and makes the truck slam into gear almost, specially from 2-3rd shifts.

Should I turn back on torque management? Remove the firm shift tune? Im sorta confused as there are no real instructions for this tuner.

Thanks in advance.

turn torque management back on..

lower shift pressure more..

get a custom tune done - www.diablewtune.com

there's a table in the ECM/engine side of the tuning that controls timing during a shift - the diablo tunes have that table jacked up high, which causes the hard shifting... only way to fix that correctly is via a custom tune...

So custom tune is what really needs to be done huh? For now, Ill turn the torque management back on and see how it goes first.

Thank you for your help.

my truck shifts much better on hard shift, the firm is just to bouncy kinda I guess is how I would describe it, try the hard and play with that??

hoorsec wrote:my truck shifts much better on hard shift, the firm is just to bouncy kinda I guess is how I would describe it, try the hard and play with that??

Ill have to look into that and see what happens. Is that with torque management on or off?

CJM8515 wrote:

hoorsec wrote:my truck shifts much better on hard shift, the firm is just to bouncy kinda I guess is how I would describe it, try the hard and play with that??

Ill have to look into that and see what happens. Is that with torque management on or off?

always off..lol..

Thanks.

Still working on this for now. Turned of torque management and the truck is pitiful. It just doesnt accelerate well. I tried to pull out rather quick from a side street and it felt like I was driving a 6 cylinder.

Maybe turn off firm shift and turn back on torque management? This sucks..

About the only positive is the truck doesnt slam into 1-2 and 3-4 now.

Guess Ill be doing a custom tune sooner or later. For now IDK wtf to do to at least get some power.