Updating Professional Tune

[Luke_K]

Hi everyone,

I have a 2008 GMC Sierra 1500 that was professionally dyno tuned for a BTR Stage 2 cam. The tune is currently in the truck and running great.

Recently my factory G80 failed, so I rebuilt the rear axle with an Eaton clutch-style posi and switched from 3.73 gears to 4.10 gears. I’m also running 35” tires.

I would like to update the gear ratio and tire size so the TCM and speedometer are correct. However, I’m concerned about overwriting my custom tune.

My Diablo Trinity was used previously to unlock the ECM before the dyno tune, but I never reset it after the shop tuned the truck. I believe the Trinity still has the original factory backup saved.

My question is:Is there a way to adjust tire size and gear ratio using the Trinity (Quick Adjust, etc.) without overwriting the custom tune currently in the truck?

I’d prefer to avoid loading a canned tune or losing the dyno calibration if possible. My tuner is about 3 hours away, so I’m hoping there’s a safe way to correct these parameters without making the trip.

Any advice from others who have done this with a custom tune would be greatly appreciated.

[06MonteSS]

Nope... Since you read out the original backup stock tunes with it, but did not restore the original backup stock tunes to the truck using the Trinity before you had it tuned with hptuners, then the trinity will not work now... because it will detect that the truck is already tuned, and the tune/calibration ID's in the ECM do not match what it was when you used it before, so now it won't let you do anything.

So no, you can't use the trinity on it now...

[Luke_K]

Would there be a way to reset the trinity and start it out fresh…?

[06MonteSS]

If it's the newer Trinity T2, you would have to buy another GM license for $170...

If it's the old Trinity T1000 - No....

[Luke_K]

I have a newer T2 and that seems like a way more reasonable option. My tunner is wanting $500 for these changes…do I need to plug my T2 in and follow steps to achieve this?

[mikel]

yeah, add a license, then plug into the truck and select the 'modify stock tune' option.
Let it read the backup, then it will let you adjust tire size/gear ratio and anything else you want to adjust on the existing tune, then install that tune back to the truck and it should be good to go.