What turns the speedometer cable? I want to use the factory 81 gauge cluster in my 74 beetle that I just put a 12A in. All the gauges are prettystraight forward except the speedo, if I know what shaft turns the cable i can figure out what the ratio difference is between the RX and my beetle cable. A little gearbox and problem solved.
Thanks, John

 

Take a look at the tailhousing of your tranny and you'll see a thick black cable. That runs all the way to your spedo. Inside is a gear that in conjunction to your tailshaft speed controls your spedo, but in your case, unless your using really big wheels your spedo should be the same as before. It might not be a direct hook-up, but everything should be fine on your guage.

 

thanks for the info but I don't have a RX7 tranny to look at, my 12A is in my 74 VW beetle connected to my VW IRS transaxle. What I need to know is what spins the actual cable on the RX7 and at what relationship to the tail shaft if that is what the cable is geared to, the VW spins the cable right off the front left wheel, So what I want to do is use my VW speedo cable and make a gearbox to alter the speed of the cable with the appropriate ratio to match what the RX7 speedo would spin at. The gearbox will just compensate for the difference in wheel size and difference in speedo cable drive mechanisms the relationship is still linear though and I know what the ratio difference is in terms of wheel size.

 

It is geared off the rear of the transmission and is geared with the drive line.