Ba F6 Ratio Change

[Benny_C]

Hi all,

I recently snapped the hemisphere in my standard BA II F6 diff and had a truetrac put in, there was a bit of an issue with the crown and pinion so they replaced the standard gear set (3.73?) with some 4.10s.

Couple of questions, will the new ratio have affected my speedo reading? Im running 20s on it so I know it'll be out anyway but unsure if this will change it more?

And something a little weird, my cruise control won't stay on in 5th gear, every other gear it works but as soon as I hit either set button it flashes on on the dash then its gone straight away, stayed on for a little bit as I went up a hill but went back to dropping out as soon as it hit the flats again.

Thanks

Ben.

[Ralph Wiggum]

Gear ratio change wont effect the Speedo, Speedo is driven off the by the signal from the ABS ECU which gets its signals from the abs sensors at the wheel.

Cruise wont work in 5th because the 4.09's will have cause a Road Speed/RPM mismatch. The pcm will be thinking " I shouldn't be doing these revs at this speed" and won't set cruise.

Your tuner needs to adjust the diff ratio in the tune.

[Benny_C]

Well there goes another $500 for a retune I guess. Ah well at least its an easy fix. Thanks for the help.

[ms700]

Rukey - should this be a issue I will need to raise with my tuner when I perform my T56 swap? Im planning on keeping my 3.45 rear end, but im guessing my revs @ 110kph will be lower with the T56 than what they were with the BTR......

[Ralph Wiggum]

Just get him to change the ratio when you ft the Manual PCM. I have only seen it raise itself as an issue when going to a lower diff ratio.