Crashtd420 Posted May 19, 2018 Report Share Posted May 19, 2018 So when i rebuild my 521 I had the wrong transmission. Short 71b 26-1/2 long from I believe an 80 720, wrong bellhousing, 17 tooth speedo gear. so I sourced a 4spd... I believe it came from a 72-73 620. Also 26-1/2 long and had a sleeved output and a 16 tooth gear in it. (Currently installed in truck) Then I came up on another 4 spd for parts because I figured why not... this was from a 521, and had the flanged output, again 26-1/2 long .... Inside was a black 17 tooth... All 3 Speedo assemblies looked like this. So this is where I am getting confused... I found this info.. But it seems to contradict other info I found.... I though the 521s and 620 came with 437 gears but when I looked Speedo assemblies up on carpartsmanual.com for part numbers It shows the 620 having the 16 tooth and the 521 with the 17, also said the 19 but I think that was referring to the j13... So on to my problem.... with the 16 tooth installed, 4.37 gears and 195/60-15 tires when my speedometer is at 40 I am only going 30.... So how do I figure out what Speedo gear I need? Putting the 17 in corrected it some but I need to take for a ride and see exactly how much.... Is there a certain speed I should be doing this at? I'm sure I will have more questions. I want to start a classified to get the correct gear I need but am currently not sure what to ask for... If anyone has spares I could try that would be sweet... I'll pay shipping back and forth, I'll buy it if it's up for sale, 19 or 20 is what I am thinking i need but I would like to try to confirm some of this info first... Edit: Just thought would this be better posted under drivetrain? If so please move... thanks.. 1 Quote Link to comment
banzai510(hainz) Posted May 19, 2018 Report Share Posted May 19, 2018 OK this is in the old nissanmotorsport Catalog increasing the tooth count on the pinion will decrease the MPH readout Depending on speedo pinion selected the alternate sleeve assemble mayb also be required 7/69-9/73 4 speed 32703- 22000 16t 22001 17t 21100 18t 78600 19t 14816 20t 25301 21t 16715 22t NLA (this is a old book) others may be NLA also 19910 23t 32707-14600 sleeve assy 16t/19t 32707-14810 20t/23t 2 Quote Link to comment
Charlie69 Posted May 19, 2018 Report Share Posted May 19, 2018 Tire height will determine what the speedometer reads. Is that chart for a car or truck. 13", 14", 15", or 16" wheels and tires. What tire height is used in correspondence with that chart? Quote Link to comment
datzenmike Posted May 19, 2018 Report Share Posted May 19, 2018 If 16 and you are out 10 MPH... 40MPH @ 30MPH? That's 33% error. Going to a 17 tooth is 6.25% change or 31.875MPH 18 tooth is 12.5% or 33.75MPH 19 tooth is 18.75% or 35.675MPH 20 tooth is 25% or 37.5MPH 21 tooth is 31.25% or 39.375MPH ...... this is as close as possible. Your tires 195/60R14s are 24.25" diameter. Stock is about 23.65" so this adds slightly to the speed and works against you. 1 Quote Link to comment
Crashtd420 Posted May 19, 2018 Author Report Share Posted May 19, 2018 If 16 and you are out 10 MPH... 40MPH @ 30MPH? That's 33% error. Going to a 17 tooth is 6.25% change or 31.875MPH 18 tooth is 12.5% or 33.75MPH 19 tooth is 18.75% or 35.675MPH 20 tooth is 25% or 37.5MPH 21 tooth is 31.25% or 39.375MPH ...... this is as close as possible. Your tires 195/60R14s are 24.25" diameter. Stock is about 23.65" so this adds slightly to the speed and works against you. Ok that last part about the tire size is a bit confusing.... I tried posting this question in my build thread with little response. one response I got was from mklotz and he said that the stock tire size would be 25.5 tall... 1 Quote Link to comment
Tucson620 Posted May 19, 2018 Report Share Posted May 19, 2018 Never had great luck with Datsun speedo accuracy BUT my franken-521 is pretty good - 4.375 gears, I believe 19T White pinion in a 280Z 5 speed, 225/60R15 tires (25.6"). None of this helps you, other than to say those tires do NOT fit, rub everywhere. :lol: But I do have a red 20T pinion gear out of a 4.11 Z laying around. Not sure I have a housing to match though. Have a 4 speed sitting - I'll check this weekend and PM you re: classified ad. 1 Quote Link to comment
datzenmike Posted May 19, 2018 Report Share Posted May 19, 2018 Ok that last part about the tire size is a bit confusing.... I tried posting this question in my build thread with little response. one response I got was from mklotz and he said that the stock tire size would be 25.5 tall... What ever a 6:00 X 14 tire is. 175/70R14 I think. 1 Quote Link to comment
Tucson620 Posted May 19, 2018 Report Share Posted May 19, 2018 Between this and the other thread (http://community.ratsun.net/topic/73826-speedometer-5-speed-tranny-swap/ ) I'm more confused. I might be mixing up truck and Z (short and long) transmissions here. Seems like your sleeve is a different length than would expect for 4 speed. Are the pinion gear shafts longer too? Here's sleeve and gear with yellow 16T out of 260Z 4 speed. Looks 0.75" or more shorter than yours. Have 20T red cog from a 4.11 Z (not clear on source) - it fits in this housing fine, but I think it's the wrong sleeve offset for gears to mesh. Don't have the proper 20-23T sleeve for it. Sleeve + gear overall length approx. 3.125", gear and shaft approx. 3.0" by itself. 1 Quote Link to comment
Charlie69 Posted May 20, 2018 Report Share Posted May 20, 2018 Easiest way is to keep the rear end ratio.and tire size the same as the doaner vehicle for the transmission to keep speedo correct. Quote Link to comment
banzai510(hainz) Posted May 21, 2018 Report Share Posted May 21, 2018 I swear my stock tire size ran 75 SERIES TIRE 1 Quote Link to comment
datzenmike Posted May 21, 2018 Report Share Posted May 21, 2018 That would make it 24.33" and basically the same and zero difference. 1 Quote Link to comment
Charlie69 Posted May 22, 2018 Report Share Posted May 22, 2018 Stock tires for a 720 are 195 75 14 or factory alloy rims 205 75 14. 195/75R14 tires have a diameter of 25.5", a section width of 7.7", and a wheel diameter of 14". The circumference is 80.1" and the revolutions per mile are 791. 205/75R14 tires have a diameter of 26.1", a section width of 8.1", and a wheel diameter of 14". The circumference is 82.0" and the revolutions per mile are 773. Quote Link to comment
Crashtd420 Posted June 12, 2018 Author Report Share Posted June 12, 2018 Well no luck here or with my classified .... everyone seems to have the short ones..... So I came up with this idea.... This is for an older mustang.... It's a 21 tooth, has same outside diameter as the datsun ones.. and the inside hole is smaller than the shaft for the datsun.... The idea is to machine the top and bottom of to match the datsun gear, then bore the inside out to fit the Speedo pinion shaft... if it works I'll post better details right now this is all a guess.... Oh and the gear was $8 so if it works great if not i am only out $8..... Last resort i will be calling these guys... need to verify the thread pitch.. And available ratios... They have a metric adaptor... they get $120 for it... 1 Quote Link to comment
datzenmike Posted June 12, 2018 Report Share Posted June 12, 2018 I want one!!!! 1 Quote Link to comment
Crashtd420 Posted June 12, 2018 Author Report Share Posted June 12, 2018 I want one!!!! I can only assume you mean the ratio adaptor... I tried emailing but never heard back... I just haven't gotten around to calling.. if you call to inquire the thread needs to be 22x1.5 to fit... 1 Quote Link to comment
Charlie69 Posted June 13, 2018 Report Share Posted June 13, 2018 Crash are you trying to get a red gear that fits a 4 speed gear box? Quote Link to comment
Crashtd420 Posted June 13, 2018 Author Report Share Posted June 13, 2018 Crash are you tring to get a red gear that fits a 4 speed gear box? Honestly I'm not sure what color I need but yes I need a gear for my 4spd, which should also work in my 5spd because the assembly was the same ... Both were the longer assemblies... The the 4.37 gears say I need a 21 tooth purple, my tire sizes might mess that up so I may only need the 20 tooth red.... 1 Quote Link to comment
Crashtd420 Posted June 14, 2018 Author Report Share Posted June 14, 2018 Well the mustang gear isn't gonna work.... first off I measured the datsun Speedo pinion shaft wrong.... It was .390, not .490 like I thought... id of gear was .450 ... Even if I measured right the gear teeth were slightly off on the angle so it wouldn't work even if I got the measurement right..... On to the expensive solution, the ratio adapter.... probably give them a call next week and get some more info.. I'll post more info about that once I find out.... 1 Quote Link to comment
kelowg Posted June 15, 2018 Report Share Posted June 15, 2018 Just get a gps speedo gauge,lol. No more guessing,broken cable or pinion gear. Or just use phone with gps app and leave stock setup be. 1 Quote Link to comment
Charlie69 Posted June 15, 2018 Report Share Posted June 15, 2018 I used a phone app from Battle Mountain Nevada to Phoenix for speedometer as My speedometer cable broke just before I left. Quote Link to comment
datzenmike Posted June 15, 2018 Report Share Posted June 15, 2018 Fuck GPS. It's for anyone born after '90 who can't drive a standard or read a map. Experience what driving a 521 was like when it was new. Earn that thumbs up out on the highway. 2 Quote Link to comment
d.p Posted June 15, 2018 Report Share Posted June 15, 2018 Fuck GPS. It's for anyone born after '90 who can't drive a standard or read a map. Experience what driving a 521 was like when it was new. Earn that thumbs up out on the highway. Lol like anyone not going to give you a thumbs up because they somehow found out you use GPS. Quote Link to comment
Crashtd420 Posted June 15, 2018 Author Report Share Posted June 15, 2018 If my speedometer was broken i would use a GPS one, but the whole instrument cluster works and actually is in good shape just the Speedo is not accurate.... Mostly I want to track the mileage... my distributor app has the speedometer in it, I usually have that on while driving... so I know how fast I'm going but it doesn't track the milage.... 1 Quote Link to comment
john510 Posted June 16, 2018 Report Share Posted June 16, 2018 Fuck GPS. It's for anyone born after '90 who can't drive a standard or read a map. Experience what driving a 521 was like when it was new. Earn that thumbs up out on the highway. Are you still using a Thomas guide to find your way around ? i just bought a new one in case all the satellites fall out of the sky. 1 Quote Link to comment
mainer311 Posted June 17, 2018 Report Share Posted June 17, 2018 Some of the crap people say on here is just absurd. Mike, did you ford the river today with your Conestoga wagon, or did you die of dysentery? I left my wife a note earlier. It took me forever to drag a big stone tablet into the kitchen, and then I lost my chisel somewhere in the cave out back. 2 Quote Link to comment
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