Away8777 Posted March 1, 2022 Report Share Posted March 1, 2022 Hello everyone I'm new to the Datsun world recently picked up a 82 regular cab 2wd 720 with the z22 in it and it's a 5speed. I'm currently working on the speedometer as it is not working I know the cable is broken and am currently trying to source a replacement. Also noticed that the pinion gear in the transmission is offset and has a blue gear on it. With the research I have done and the confusion that I have is that I should have the white gear with opposite offset. The mounting bolt for the pinion gear is at the bottom in the 6oclock position. Any help identifying what transmission this is or where the markings would be and what parts I need would be greatly appreciated. Quote Link to comment
Away8777 Posted June 19, 2022 Author Report Share Posted June 19, 2022 I'm picking this back up hopefully someone has an idea. I found out my cable was broken and swapped it out with one from napa. The speedo works now and I had my wife follow me on a short trip and it seems like the Speedo reads about 5mph higher then my actual speed. I'm wondering if it's just how these trucks are or is it because the pinon gear I have shown is not the right one any insight would be great thanks. Quote Link to comment
datzenmike Posted June 19, 2022 Report Share Posted June 19, 2022 How do you know it's the wrong pinion gear? Was the transmission changed? Be absolutely sure that you are 5% fast and you can go to a different gear with more teeth. 5% is 2.5 MPH @ 50 or 5 MPH @ 100MPH. More teeth will turn the speedometer slower for the same turns by the transmission Blue is 18 tooth. A white gear is 19 tooth and 19/18=5.555 % difference. Looks like you want a white gear. You might find it easier to drive a measured distance using mile markers on the highway and use your odometer. Quote Link to comment
Away8777 Posted June 20, 2022 Author Report Share Posted June 20, 2022 Thanks Mike for the info I have the 5 speed manual transmission. I am honestly not sure if it is the original transmission or not. I believe I saw somewhere on a form that the white is what would have came with the 5speed 720 transmission. With my wife in her new Subaru next to me her car reading 30mph my truck was at 35mph. At 35mph the truck was reading 40mph. I will source a white gear and see if it fixes this issue. Quote Link to comment
datzenmike Posted June 20, 2022 Report Share Posted June 20, 2022 There are multiple differential ratios and tire and rim choices for the 720 so many many speedometer gear options. If 5 MPH out across the board at all speeds, then changing the gear won't really help much. That I believe is a problem in the speedometer head. A speedometer that is out 2 MPH at 20 (say the wrong tires) will be 4 MPH out at 40 and 8 at 80 and so on. Double the speed doubles the error. 5% at 30 MPG is 1.5 MPH out 5% at 35 MPH is 1.75 MPH out 5% at 40 MPH is 2 MPH 5% at 60 MPH is 3 MPH 5% at 90 MPH is 4.5 MPH 5% at 100 MPH is 5 MPH Quote Link to comment
Away8777 Posted June 20, 2022 Author Report Share Posted June 20, 2022 Ok that makes sense. I do have the 4wd rims with slightly stretched tires to help clear the fenders as the truck is lowered I just had to be sure I'll do some more testing see if I can get a more accurate reading and number to document the speeds between my wife's car and mine. I honestly haven't had this truck over 40mph now that I'm thinking about it. Thank you Quote Link to comment
datzenmike Posted June 20, 2022 Report Share Posted June 20, 2022 The error must increase with the speed. It might be easier and a lot more accurate to use mile markers and your odometer. Go at least 20 miles and read the odometer. If 19.5 or 20.5 that's 2.5% out or 2.5 MPH at 100 MPH half that at 50 MPH. Hardly worth worrying about and the gear in the transmission is correct. Follow a moving car at 25 and again at 50 MPH and see what your meter reads. Research shows an 18 tooth pinion gear for the '82 standard cab short wheelbase truck. This tentatively agrees with what you have. Quote Link to comment
Away8777 Posted June 20, 2022 Author Report Share Posted June 20, 2022 Alright I'll do this test next time I have it out it doesn't really bother me too much as it's not a daily by any means and usually only use the truck for short trips to local meets and maybe to get ice cream with the wife. Thank you Mike for all your help. Quote Link to comment
datzenmike Posted June 20, 2022 Report Share Posted June 20, 2022 I like Nissan puzzles. What size tires do you have on it? Quote Link to comment
Away8777 Posted June 20, 2022 Author Report Share Posted June 20, 2022 Off the top of my head I want to say 205/65r15. I can get you the exact size when I get home. Quote Link to comment
Away8777 Posted June 20, 2022 Author Report Share Posted June 20, 2022 Mike the tire size on my truck is in fact 205/65r15 Quote Link to comment
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