Hi everyone. This post may get complicated but I hope it makes sense to everyone I have the running gear from a r31 skyline, engine and gearbox and ECU from Holden. And I've researched on here and I've found that my diff ratio is 3:45, and the R31's are 3.7/3.89/3.9.......so is that generally why my speedo is out? At 80km on my cluster it showed 94km on a speed reading thing on the highway as I was travelling home on the highway from Torquay. Also how does this affect my revs and gear changes? Is my gearing longer or shorter - it really confuses me but thats how im going to word it. For example I am sitting just under 2,000rpm at 80km on my speedo - as stated above is believed to be 94km. And again just under 2,000rpm when doing around 60km. Also I can't really tell when its kicked into overdrive 4th....? My understanding of ratios in gearboxes and differentials is pretty good but I get confused when its fairly technical. Any information will be most helpful towards sorting out my issue. Regards, Tim.

Yes that is why your speedo is out. I have the same thing. R31 gearbox and my speedo is out

Quote: Originally Posted by vinny mac [View Post] Yes that is why your speedo is out. I have the same thing. R31 gearbox and my speedo is out Hey mate, thanks for posting. Is it worth complaining to my mechanic about it? The work was done nearly a year ago but i have been back and fourth to him about a on going high fuel usage issue.

sort out your fueling issue mate, he will tell you it was your choice to put the running gear in (should have warned you to be honest). Get it running properly, and then consider your options imo

Quote: Originally Posted by vinny mac [View Post] Yes that is why your speedo is out. I have the same thing. R31 gearbox and my speedo is out Hey mate just wondering how much is it off by? I used the GPS device ona trip to heathcote and I was out by 8-6km all the time. like 52km was 60 and 92 - 94km was 100km. thanks mate. Figured out I need a speedo drive from a VL tranmission