datsunaholic Posted July 12, 2012 Report Share Posted July 12, 2012 What were the 521 options? A PL521 (70-72) was 4.375. A L521 (68-69) was 4.889. 620 rears were normally 4.375 as well. There were exceptions- 73-74 Automatics were 4.625. '79 Manual transmissions were 4.111. '73 Heavy-duty may have had 4.88s. "Running out of 5th on the freeway" is next to impossible. With a 5-speed and any rear end, even a 4.88, you'd be pretty much doing 100MPH by the time you hit 5600 RPM. With a common 4.375 you'd be over 110MPH @ 5600 RPM. More likely you're running out of horsepower, and changing gear ratios won't help. Every year I go cross state. I've run for hours at 80MPH with a 4-speed, stock rear end 620 King Cab. That included climbing mountain passes, but more telling is I ran up the inclines out of Vantage doing 80. The only mod I have is a Weber. It pulls it just fine. 1 Quote Link to comment
what Posted February 25, 2013 Report Share Posted February 25, 2013 If anybody is interested I have the center section out of a 720 2wd with 3.89 gear ratio. Send me a p.m. if interested. $100.00. No shipping. Its to heavy. Quote Link to comment
Jayden71 Posted March 15, 2013 Report Share Posted March 15, 2013 A PL521 (70-72) was 4.375.A L521 (68-69) was 4.889. 620 rears were normally 4.375 as well. There were exceptions- 73-74 Automatics were 4.625. '79 Manual transmissions were 4.111. '73 Heavy-duty may have had 4.88s. "Running out of 5th on the freeway" is next to impossible. With a 5-speed and any rear end, even a 4.88, you'd be pretty much doing 100MPH by the time you hit 5600 RPM. With a common 4.375 you'd be over 110MPH @ 5600 RPM. More likely you're running out of horsepower, and changing gear ratios won't help. Every year I go cross state. I've run for hours at 80MPH with a 4-speed, stock rear end 620 King Cab. That included climbing mountain passes, but more telling is I ran up the inclines out of Vantage doing 80. The only mod I have is a Weber. It pulls it just fine. I have dogleg in my 521 with 488s, I am now turning approx 3700rpm at 65mph. I'm running 215/70/R14s. I am in love with it :thumbup: Quote Link to comment
minitrucker80 Posted October 22, 2013 Report Share Posted October 22, 2013 I have a 71 521 rearend in my 720....will the 3rd member out of a hardbody work in it..both are h190 rearends Quote Link to comment
]2eDeYe Posted October 24, 2013 Report Share Posted October 24, 2013 Yes, they should swap. Quote Link to comment
green180 Posted October 27, 2013 Report Share Posted October 27, 2013 I pulled the gears out of an 83 720 5 speed and ended up with 37:10 gears, hopefully my little l16 won't be too slow with 3.7 gears, were 3.7 gears supposed to be in 5 speeds, and would the speedo gear just swap over Quote Link to comment
wayno Posted October 27, 2013 Report Share Posted October 27, 2013 I pulled the gears out of an 83 720 5 speed and ended up with 37:10 gears, hopefully my little l16 won't be too slow with 3.7 gears, were 3.7 gears supposed to be in 5 speeds, and would the speedo gear just swap over You will likely not be able to haul loads with them gears, the L16 is not known for having torque. Quote Link to comment
datzenmike Posted October 27, 2013 Report Share Posted October 27, 2013 I pulled the gears out of an 83 720 5 speed and ended up with 37:10 gears, hopefully my little l16 won't be too slow with 3.7 gears, were 3.7 gears supposed to be in 5 speeds, and would the speedo gear just swap over No, speedo gear won't swap over. Your 521 should have a 189 tooth mated to a 4.375 ratio diff. To go down to 3.7 ratio you need to slow the speedo down about 18%. A 16 tooth pinion is almost perfect. You could try a speedometer pinion (this is just the plastic gear, about $20) from a 510 32703-22000. Also found in 610/710 and early 620s. If looking the gears are Yellow plastic. Quote Link to comment
Calbuzzard67 Posted July 14, 2014 Report Share Posted July 14, 2014 So what is the diff ratio on the 720 ? Quote Link to comment
Calbuzzard67 Posted July 14, 2014 Report Share Posted July 14, 2014 So what is the diff ratio on the 720 ? I found my answer in another post Quote Link to comment
Blazed22s Posted November 3, 2014 Report Share Posted November 3, 2014 So I have read through this post, and tried to do a little bit of research in other places, but I still have a question. The only way to lower the gear ratio in my 1971 521 truck is to get a whole center section out of another truck? No one sells a gear set that I can buy either online or a parts store? I put a chevy 4.3L v6 and 5speed in my truck out of an 1991 s10. I'd like to get a lower gear ratio, something closer to what the stock s10 had. I pretty much have no 1st gear at the moment, revs out super quick. I really dont have time to go junk yard shopping around here. Finding any kind of Nissan truck, much less a datsun truck in a yard is near impossible. I'm just wondering if that will be my only option (other than spending bookoo bucks on a whole new custom rear end). Quote Link to comment
wayno Posted November 3, 2014 Report Share Posted November 3, 2014 Just find a Nissan 720 with an H190 with 390/370/350/330 gears and put it in your truck, the thing about doing it this way is there is nothing to set up, you just remove your center pumpkin/gearset, and put the one out of the 720 with an H190 in your 521, fill it with gear lube and your good to go, it takes less than 2 hours. What gearing did the S10 have? So I have read through this post, and tried to do a little bit of research in other places, but I still have a question. The only way to lower the gear ratio in my 1971 521 truck is to get a whole center section out of another truck? No one sells a gear set that I can buy either online or a parts store? I put a chevy 4.3L v6 and 5speed in my truck out of an 1991 s10. I'd like to get a lower gear ratio, something closer to what the stock s10 had. I pretty much have no 1st gear at the moment, revs out super quick. I really dont have time to go junk yard shopping around here. Finding any kind of Nissan truck, much less a datsun truck in a yard is near impossible. I'm just wondering if that will be my only option (other than spending bookoo bucks on a whole new custom rear end). Quote Link to comment
Blazed22s Posted November 3, 2014 Report Share Posted November 3, 2014 Not sure what the s10 had, but i do believe that it didnt go through first gear in 1.2 seconds. If i could find a 720 in a yard around here, it wouldn't be that bad of task. But finding a donor truck is the problem. Quote Link to comment
wayno Posted November 3, 2014 Report Share Posted November 3, 2014 I understand, maybe someone closer to you has a pumpkin/gearset, and it likely will be cheaper than what they are getting for parts around here at the wrecking yards, I have what you want, but by the time it got to you, it would be close to if not at $200.00 shipped. Perhaps you can contact members that are close to you and ask if any of them have better gearing, there are a few members in your area sort of. Not sure what the s10 had, but i do believe that it didnt go through first gear in 1.2 seconds. If i could find a 720 in a yard around here, it wouldn't be that bad of task. But finding a donor truck is the problem. Quote Link to comment
datzenmike Posted November 3, 2014 Report Share Posted November 3, 2014 There were several cars with the H-190. The '78-'84 810/Maxima wagon and the '82-'83 S110 200sx and the '84 S12 200sx all had the H-190 but different axle splines. Easy enough to slip your truck side gears into them. 1 Quote Link to comment
]2eDeYe Posted November 4, 2014 Report Share Posted November 4, 2014 You can also find them in 2wd hardbodys and frontiers up to a certain year, not sure what the cutoff year is. The h190 is pretty easy to identify though, the late model axles (non H190) have a removable plate on the back of the diff. 1 Quote Link to comment
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