When I install my GTUs rear diff, I assume that my speedo will be off a bit because of the different gearing. I was just wondering approx. how much it will be off? I think it will read high, but I could be backwards. Is there anyway to fix it? Thanks

 

maybe this will help:
http://members.ij.net/mrmazda/speedo.html

 

If you can, get the speedo gear from the GTUs transmission. 1 bolt holds it on, it will slip into place of yours, and it will keep your speedo accurate.