:classic: Is there any one out there that can tell me the aprox difference there will be when I change diff. , that is at say 60mph . Presently I am running 3.54 s and am installing 3.70 not a big jump ,but I was wondering what to expect after all is completed. I am going from a good R-180 to a newer R200 just wondered if it was worth the effort , thanks for the input stupid:

You won't see much of a difference at 60 mph in fourth gear (standard 240Z 4 speed trany) running 206/60/14 tires.

Only 132 rpm.

Here's the site that has the calculator I used.

http://www.geocities.com/z_design_studio/