Diff ratio change - recalibration

[00SS]

Hi all,

I have a factory VTII SS auto. I’m about to get a rebuild on the lsd and change out the diff gears to new 3.46 from the old 3.07.

Following that I am getting an ECU tune and dyno.

I understand some parameters will be out upon changing the gear ratio. The tuner is a couple of hundred kms away so I am wondering which parameters need to be adjusted (i.e. speedo or shift points?) to drive the car safely to the tuner? Or is it best to take the car to the tuner on a trailer?

 

[markalan1two]

your traction control will be going wild, turn that off and it should be ok, your speedo will be wrong obviously

 

[Ginger Beer]

Change rear gear settings in PCM, may need HPTuners software

As long as it isn't locked anyone with the software can do it

If it is locked contact the tuner that locked it

Changing it takes 1 minute

 

[07GTS]

only correct the speed reading and that will fix the shift points too, i think some scan tools can do those or tuners

 

[00SS]

only correct the speed reading and that will fix the shift points too, i think some scan tools can do those or tuners

Is this the ppk setting? Once it is corrected the car will be safe to drive, at least to the tuner who I would ask to calibrate on the dyno?

 

[07GTS]

yes ppk just adjust value to suit how far out u are, increase the value by the percentage ur speedo is out

 

[Aus78Formula]

Let us know how you go. I also have a mild VX LS1 and wanted to do same gears, give it a bit more around town as a bit low revving but also not lose ability to cruise on highway.

 

[Ginger Beer]

My VX SS has 3.46 truetrac, sits at hwy speeds nice

I did have 3.91, but went to 3.46 because PD

If I was going to do it again I would look at 3.07, or even 2.87 as I do alot of hwy, but, as stated, with a PD it doesn't need high revs to make power

 

[mirrabucca]

The dyno blokes should be able to adjust the PPK value while they are tuning the car.
To get there, just use your phone as a GPS to check speed.