I have a 1970 240Z with the original real end, but with a later model 4-speed manual tranny. The Speedo is reading about 10 mph low at 60 m.p.h. I don't know which speedo cog I have. I think it's the black one. Which one will increase the speed? Should I count the teeth and go to one with more teeth?

Coop

I think you need less teeth so it will turn faster

You should check the colour of your speedo gear. If its a manual with the original rear end it should have 3.364:1 diff ratio. The auto's had 3.545:1.

The 280Z had the 3.545:1 in the manual and autos (R180 and R200). If the transmission came out of this model it will be reading off.

The speedo gear should be black (17 teeth) for the 280Z with 3.545:1 Diff.

You should need yellow colour with 16 teeth. Im not completly 100% sure of the part number. You could check with your local dealer. 16 teeth Speedo pinion (Yellow) P/N: 32703-P2616

Good luck.

Chas

Edited July 2, 201412 yr by EuroDat

Is the speedo showing about 10mph low at all speeds? If so, you could just calibrate the needle in the speedometer.

I'm not the one with the Captain Obvious avatar, but can't you just drive faster?