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Speedometer Gear Issues


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Figure out how much off your speedo is first. You have to know where you are to know how to get where you're going. Lets assume that (for argument sake) you are reading 55 MPH but are really going 50, so 5 MPH or 10% out.


If you have a dogleg then you have a 17 tooth pinion gear. You need a gear that will slow by 10% or 1.7 teeth , which obviously is impossible. So go to the next largest number 2. An increase of two teeth makes it 17+2=19 tooth pinion. This is .3% too much but only amounts to 1/3 MPH at 100 MPH so no worries.

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Anyway, I'll take a sample with me and go hunting for cartridges at Pull and save today. If I find one that looks promising, I'll try and get two. That way 510er will have one!


I have been following this religously! thanks for thinking of me bro!

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You can try Matt but they have different part numbers for the sleeves and the plastic pinion gears.


I did try the optional 5 speed for the B-210... it also used the same FS5W63A dogleg but with an A series front case. The speedo sleeve and pinion gear will fit in your tranny.. but it's for a 16 tooth and is no help.


Take some pictures of it/them.

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I do have the dogleg, but I swapped in the stock 4 speed cartridge when I switched it over, so it should be a 19 tooth one now. As far as actual speed off, I'm way off, like more than 20 mph off, so finding actual is a little hard. Still haven't made it out to pull and slave but will here in another hour.

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As I mentioned the sleeve from a 4 speed from a 510 will fit the dogleg, I wasn't sure the gear would as the numbers are different. If you got it to work ... this is good to know.


510s used 16, 17, 18 tooth gears.

520s used 19 tooth (J13)

521s used 17 tooth (L16)

710s and 610s used 16 and 17 tooth

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Well that's the question. Only 63 series trannys apparently.There were no 21 tooth in stock FS5W63A dogleg equipped cars. They may be available only from the dealer.


Here are ones that I collected over the years. The two on the right are from B series 5 spd. trannys. The aluminum ones are almost always from ZX280s.The one on the left is I think from a 63 series 4 speed. No way they will swap.




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Okay, here's the scoop! The long cartridge is the stock one out of the '77 200sx short trans. (63)

The short one is out of a '77 or '78 620 long trans (71)




The sleeves are indeed different, HOWEVER, I'm pretty sure judging by the location of the roll pin, the gears can be interchanged, thus working. The red one should be the 4.375, which I'll try first. Mainly because I got to pull and save late and this was the first 620 I found that was around the right year and didn't have a huge puddle next to it. Plus I haven't been able to find axle identifications on the 620 plates very often. They're on the later cars, not sure when they started putting axle types on.


Anyway, I'll eat dinner and then try and disassemble/reassemble. Still have to yank my gear out and see if it's going to work in that sleeve, etc. So far, it looks promising.

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I tried to remove a plastic gear once. Dont, it's molded on and won't come off without breaking it off.


The 620 gear is on a spindle and it may be too short. I hope this will swap.



I also asked about gear swapping and did some research. If you go to a larger diameter, wouldn't the gears crush together too tightly??? If much smaller, wouldn't they not mesh at all???


Look at the difference in size between the black 17 and red 20 tooth gears. How does this work?



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HAHAHAHHAHAHAHA!! ROFL!! Dammit Mike, get OUT of MY HEAD!!! :D I was just going to try and remove one of the plastic gears!


Here's what the internals look like. A 3/32 punch is actually too big. It was a tight fit even after I took 150 grit to it and hit it on the wire wheel. I had to tap one out because I apparently pushed a little material with the punch. And I gouged them on the vise, but I can take those marks off the shaft on the grinder since they seal on the o-ring. They are a one-piece thing, and one's longer. So no, it won't work, maybe I should just see if Nissan can still get the speedo gear for all this trouble? :)




Mike, How did you attempt to remove the plastic gear? I was almost thinking of playing with my oven at a low temperature, or does it have that knurled surface where it just destroys it on removal?


As for the different sizes of the gear, I don't know, I wondered that too. They clearly use different ratios in the same transmissions, but I don't know enough about the internals. I was going to poke in there with a light and a probe when I took the cartridge out of mine just to see if it had some tension shaft or something?

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I was almost thinking of playing with my oven at a low temperature, or does it have that knurled surface where it just destroys it on removal?



Damn, get out of MY head!!!! I'd forgotten but yeah I think it was knurled! Maybe press it off and JB onto the longer spindle?


The one in my '70 dart was on a eccentric. You install, and the tail stock had the rear end gear ratios cast into it in a circle around the cog. You just turn the correct pinion to the correct ratio and the teeth would engage properly.

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Hmm, maybe I'll still try it with the crap gear and see if I can figure out a way. It would certainly be nice. I never did price out the piece from Nissan. It's going to really piss me off if it's a 15 dollar piece. I'm only into it for $2.87 from PNS and my time right now, but that's probably already surpassed $15. :)

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Yeah I was wondering that. There is a slot for the keeper to lock it in plac,. and the pinion is offset to one side but this would require a different sleeve for each pinion. There is only one part number for the sleeve for up to '80 and another after. and for steel or aluminum body. I talked with a guy on a Z forum and explained the larger/smaller diameter problem with mesh and he said the roll pin could be removed like what Matt did and the spindle swapped with the different gear on it. So I gave up. I wanted a different tooth gear for my truck because of 33" tires. I simply pulled the whole sleeve from a different tranny with blue 17 tooth gear. Close enough.



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I keep thinking of odd ways it would work, but yeah, I just don't know. Maybe the inner gear that turns the speedo is on an adjustable tensioner? Doesn't seem right. I may yank apart the old 4 speed just to see what the deal is on that. Ooo, wait, I just remembered the cartridge is out of it already. I'll go to the garage and shine a light in.

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I have pictures! Hold on, uploading.


Here they are:






You can see the worm gear off the mainshaft. The gear cartridge is on an eccentric.


I have two theories:


1. The gear cartridge having the large slot, can be rotated a fair amount, possibly enough to compensate for the bigger diameter gear on the end. However the tab is flat on the end, so it only seems possible that the gear fits at x degree and x degree only.


2. Since the mainshaft worm obviously doesn't move up and down, perhaps the change is in the speedometer itself? Maybe they used a different speedometer in vehicles other than the Z car?


3. I yanked the cartridge from my 5 speed (was the o.e. in the 4 speed.) It's a 17 tooth black, yet was set up for the original 3.90 ratio in the 510.


4. Considering the same gear was in the 200sx trans, yet the gears were 3.54 or something, perhaps it was only tire difference, or a different speedometer.


5. I have not checked Subarus yet to see if they have a similar gear cartridge due to the parts sharing from Fuji Heavy Industries.


6. One thing I'm pretty sure on: I don't think the 20 tooth big gear is going to fit in my case. I'm beginning to wonder about separate worms for different transmissions.


7. Are there any gears in the speedometer guage itself? Or does it rely solely on the spinning of the speedo cable?

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Lovin this thread man! After multiple trips to the JYs in my area..and beyond :rolleyes:

I have yet to find the color of speedo cog that I think I need...I love to see how you are getting all sorts of great responses from these guys!


Are you saying that if the offset of the speedo pinion (the part that you can take out) is clocked differently (turned) in the trans that it will somehow yield a different reading on the speedo? I really do NOT think so...as for all the other great comments on here I am starting to see that another trip to the Nissan dealer just might be in order...look forward to seeing the end results. :cool:

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There is no provision for changing the gearing on the speedometer. At a given speedometer cable RPM, it should always read the same speed.

The gear on the output shaft of the transmission is a fairly shallow spiral gear, and the speedometer pinion is slowed down about 4 to 1, compared the driveshaft RPM.

If you have a tachometer for the engine, in fourth gear, with a 1 to 1 ratio in the transmission, engine RPM is driveshaft RPM.

Since there were two different sleeves to hold the speedometer pinion available, one for smaller gears, and one for larger gears, that is how the difference in diameter was accommodated. The fit, or mesh of the gears does not have to be perfect, since the speedometer does not really need a lot of power to drive it, if the cable is good.

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Back from Pull n Slave! Found out a bunch of things.


1. Speedometers are the same. I compared one off a 620 with the red 20 tooth gear and one from a 610 with probably a 3.90 gear and both said "60 mph = 1024 rpm" at the bottom below the part you can see when the dash is on. It's also probably near impossible to change any gears in the speedometer itself. Fairly compact and funky little plastic gears and worm assemblies.


2. Checked the Subarus, Toyotas, and other Nissans. The two cartridges are uniques to rear drive Datsuns of the two tranny styles only (63 and 71).


3. What it leads me to think is that I won't find a 20 tooth red gear to fit in the long cartridge since no Datsuns with the short transmission I know of ever came with a 4.11 or 4.375 gear ratio and even with it on there, it won't mesh properly with the transmission gear. It will be way too large a circle to engage.


4. So basically I need to either buy a speedometer with a magnetic pickup (expensive) or retrofit something else like Buddy's '04 Wrangler. It has an eccentric like the 70's Dart Datzenmike mentioned earlier, and you switch it to whatever gear ratio you have.


5. The only other option is a gear reducer box which I can't seem to find, though I have seen pictures.

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Are you saying that if the offset of the speedo pinion (the part that you can take out) is clocked differently (turned) in the trans that it will somehow yield a different reading on the speedo? I really do NOT think so...as for all the other great comments on here


No, I meant that if you rotate it, it might move the speedometer gear circle enough so a larger diameter speedo gear would mesh with the worm in the tailshaft, but I think the 20 tooth is just plain too big, when compared to the size of the 17 tooth.

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I LIED!!! :)


I'm so freakin' happy I'm an anal-retentive bastard! So I decided I'd just throw the short gear speedo gear stem in the long cartridge and go stick it in to see if I could get it to work. It does! I still need a long stem red gear which I'll probably get from Nissan if they're still available. The only thing you'll need to do is take out your old cartridge, swap gear stems, then grind another channel 180 degrees from the original channel, flip it over, and install!


These are fitted on the original 510 4 speed.






And now I'm head bangin'! :D



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