5 speedometer drive gear

[69roadster]

, I have  a U20 with a 5 speedometer installed in my 67.5 SPL.  Running the 3.90 rear end from the 1600. My speedometer is off. At 3500 ramp the speedometer reads 80 MPH. Does anyone know which drive drive gear gear I need to correct the speedometer .

 Thanks 

[rwmann]

Without knowing what speedometer pinion you presently have in your 5 speed, or what diameter rear tires you are running, the best way to do this would be to compare speedometer indicated speed over a range of speeds to GPS speed (for a cell phone or GPS unit), or clock time over a measured mile at constant speedometer indicated 60 mph, then use that ratio to determine what pinion to look for. If the 5 speed has an 18 tooth (blue) or 19 tooth (white) pinion and you are indicating 10% high, choose a pinion with 10% more teeth (20 tooth red pinion for 18, or 21 tooth purple for 19).

[mraitch]

see write up in Tech - Ross has an article and I do about pinion/carrier issues!

[Datsunparts.comInc]

Without knowing what speedometer pinion you presently have in your 5 speed, or what diameter rear tires you are running, the best way to do this would be to compare speedometer indicated speed over a range of speeds to GPS speed (for a cell phone or GPS unit), or clock time over a measured mile at constant speedometer indicated 60 mph, then use that ratio to determine what pinion to look for. If the 5 speed has an 18 tooth (blue) or 19 tooth (white) pinion and you are indicating 10% high, choose a pinion with 10% more teeth (20 tooth red pinion for 18, or 21 tooth purple for 19).

These are what I have in stock:

https://www.datsunparts.com/1721
https://www.datsunparts.com/2740
https://www.datsunparts.com/2106
https://www.datsunparts.com/2741
https://www.datsunparts.com/2742

Dean

[70MTRoadster]

I have a 70 1600 with a 5 speed and U20. I have the 3.90 rear end. I took my blue toothed gear out of the 5 speed. I noted the offset of the gear in relation to the carrier. The carrier is oriented with a slot at 12 o'clock to be retained there by a bolt and tab. I took that carrier, machined another slot 180 degrees from the stock one (this gave me the correct protrusion with the Red 20 tooth gear) and reintalled. Speedo is right on the money. Tires are 185-65-R14.

Scott

[rwmann]

Scott is correct about the pinion carrier clocking difference. In addition, there are two pinion carriers, with pinions 20 teeth and above normally installed as a complete unit in the alternate carrier, which if installed in a Roadster 5-speed, needs an alternate 60-degree retainer slot cut.

[69roadster]

I'm running 195/55/15 I would have to pull the speedometer gear to see which one I have.