Zedman240®

First make sure your speedo cable hasnt broken, take it out and check its length. Then get underneath and check the diff ratio yourself. Count how many times you turn the input shaft so one of the wheels (if you dont have a lsd) turns once. And check what color your original speedo drive gear is to the other one in the manual trans. I have been looking everywhere for a list of which color speedo drive equals what diff ratio you are using to get speedo accuracy! I went to Nissan and bought a black one coz my speedo is way out....and because its a 69er ,its in Mph. If someone has that list please let me know! it will help alot of people!! Hope that helps a little.

The output shafts on the 280's are CV's so you will have to get some 260 output flanges. Not sure on the input shaft tho, just have to measure! hope that helps..

I think the only major difference is in the 1st gear ratios, 260 has a 2.90 and the 280ZX has a 3.20. So if your happy with a shorter first, lovely! Also depends what diff ratio you are running...