Diff Ratio change

[hiboost]

Hi all,

Customer has had the diff ratio changed in his 07 BF XR6 turbo with ZF 6speed to 3:23 from 2:73, to change the ratio in the PCM calibration do I just alter auF0394 or is there another area that needs changing?

I have changed the auF0394 value to 3:23 and when I checked for codes after the road test I have code P1934 vehicle speed signal, car drives okay.

Thanks Neil

[BeerTurbo]

How does it go with full throttle changes? when i changed my ba na from 3.32 to 3.73 diff the auto would hit redline before changing.

as the auto shift points are set based on road speed not RPM you may need to go through and adjust the high end shift points. 

you may want to double check cruse control still works also, ive heard diff changes play havock on that. 

[hiboost]

Shifts are fine car feels normal slight flare under boost on 3-4 gear change but other than that its fine, haven't checked the cruise to see if that works i'll go check that shortly.

I might just try flashing it back to std and see if the code stays or goes away before I delve into the tune much further.

 

Thanks Neil

[Roland@pcmtec]

Gear shifts are done in oss, if you change the diff it shouldn't affect these. Going to a lower ratio should also slow the speed it revs down mean in g less chance of hitting redline. Doing the opposite will do what you described though. 

[bos330]

On 5/22/2019 at 9:15 PM, hiboost said:

Hi all,

Customer has had the diff ratio changed in his 07 BF XR6 turbo with ZF 6speed to 3:23 from 2:73, to change the ratio in the PCM calibration do I just alter auF0394 or is there another area that needs changing?

I have changed the auF0394 value to 3:23 and when I checked for codes after the road test I have code P1934 vehicle speed signal, car drives okay.

Thanks Neil

Hi Mate slightly off topic but how did the xr6t and the zf overall respond to the 3.23 gears. id imagine its a very good gear choice only 1st gear being very tall.