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620 Speedometer Pinion Interchangeability


Toxocara

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I have a 1973 620 with a 4 speed manual. The speedo pinion is flat and barely runs the speedometer.  Its a 16 tooth, can't find anything available accept for one eBay listing. Part number 32703-22000 (thanks Mike). I believer that this is the right part, it's "only" 40 bucks, but I can see that I can find Z pinions all day long. Specifically a 17 tooth for a 70-71 240Z. However, I can't find the OE part numbers for these, dealership websites are so bad for these old trucks. 

 

My question boils down to, what vehicles/transmissions have interchangeable speedometer pinions with the 73 620 transmission? I'm willing for my speedo to be off a touch if I can get it to work at all, and hunting down parts for these early 620s has been a nightmare. 

 

As an aside, can I get a double confirmation that PN: 32703-22000 is the same 16t pinion that is meant for the 1973 Datsun 620 4 speed manual? I will just get that NOS on eBay if so. Thank you!

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Okay so more research turned up a few things. That PN is correct, however, the original tires for the truck were a 6.00-14 which seems to equal a 175/70R14 which is a 23.6" diameter. I am currently running a 205/65R15 which is a 25.5" diameter. 

The bigger tire should mean that the speedometer will read a slower speed than I am actually going. To correct this, I believe I would need a speedometer pinion with fewer teeth to make it read faster. However, I don't think that there are pinions out there with less teeth. So it seems like I should just get a 16 tooth in the mean time, deal with the slower speedo, and got to a GPS speedo someday if I care enough? 

Just looking for an idiot/sanity check here.  

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Yup there are no 15 or 14 tooth pinions. Get the eBay one.

 

Your speedometer will be out about 8%. (you're going 4 MPH faster than what you are reading @ 50 MPH) Keep your eyes open for a '73 automatic 620. They have a 4.625 differential. This would remove almost 6% of your actual speed. That would be 2% or 1 MPH @ 50 MPH.

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