ZDoctor Posted July 9, 2019 Share Posted July 9, 2019 I have a 1974 260z with a Chevy 327 and bigger cams. I'm thinking about putting in a 3.90 diff off of a 240sx. Are the RPMs going to be too high on the freeway? Anyone else with that setup?Thanks in advance! Quote Link to comment Share on other sites More sharing options...
jhm Posted July 9, 2019 Share Posted July 9, 2019 What transmission are you using? And wheel/tire size? Quote Link to comment Share on other sites More sharing options...
Ben280 Posted July 9, 2019 Share Posted July 9, 2019 I'm running a 240sx transmission, a 3.90 diff and a 23.5" tall tire. 4th gear (which is 1.000 in the trans) does about 54mph at 3k RPM. A more normal tire size at around 25" would get you to 57mph at 3k RPM. https://spicerparts.com/calculators/transmission-ratio-rpm-calculator Pretty good calculator for doing the math, once you know your transmission ratios. Can play around with rear end ratios and figure out what you want for top speed. Quote Link to comment Share on other sites More sharing options...
Miles Posted July 9, 2019 Share Posted July 9, 2019 How do you use the car? Daily driver? Race car? Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 9, 2019 Share Posted July 9, 2019 You know the diff from a 240sx doesn't just bolt up right? It's a completely different diff housing and will require lots of fab work or money for custom parts/axles. Either way, how usable your car will be for every day driving will really come down to how tall your last gear is. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 10, 2019 Share Posted July 10, 2019 I thought the S12 240SX had the long nose R200. Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 10, 2019 Share Posted July 10, 2019 In Americaland the S12 was sold as a 200sx. From the scattered bits of info I can find, they came with an R180. I could be wrong on that though. Quote Link to comment Share on other sites More sharing options...
Miles Posted July 11, 2019 Share Posted July 11, 2019 (edited) Many R200 3.9 differentials used in Z cars. Pick one and you will be miles ahead............................. http://www.zhome.com/ZCMnL/tech/GearRatios.html 240Z 70-73 MT (3.364) (R180) 240Z 70-73 MT 5spd. (3.900) (R180) - non US 240Z 71-73 Auto (3.545) (R180) 260Z 74 MT (3.364) (R180) 260Z 74 Auto (3.545) (R180) 280Z 75-76 (3.545) (R200) 280Z 77-78 MT (3.545) (R200) 280Z 77-78 Auto (3.545) (R180) 280ZX 79 MT,4 Spd,2 Seater (3.364) (R180) 280ZX 79 MT,5 Spd,2 Seater (3.364) (R180) 280ZX 79 All With Automatic(3.545) (R180) 280ZX 79 MT,4 Spd,4 Seater (3.364) (R200) 280ZX 79 MT,5 Spd,4 Seater (3.7) (R200) 280ZX-GL 79 (3.7) (R200) 280ZX 80 MT,2 Seater (3.545) (R180) 280ZX 80 Automatic 2/4Seat (3.545) (R180) 280ZX 80 MT,4 Seater (3.9) (R200) 280ZX-GL 80 (3.9) (R200) 280ZX 81-83 Automatic all (3.545) (R180) 280ZX 81-83 Turbo - all (3.545) (R200) 280ZX 81-83 MT (3.9) (R200) - - - - 300ZX's - - - - - -- - 300ZX 84-86 MT and A/T (3.7) (R200) 300ZX 84-86 Turbo MT and A/T (3.54) (R200) 300ZX 87-89 MT and A/T (3.9 ) (R200) 300ZX 87-89 MT and A/T (3.9 ) (R200) 300ZX 87-89 Turbo MT and A/T (3.7 ) (R200) Note Turbos: #1) after 4/87 only-(3.7 Clutch Type LSD) 2) 88 All White SS used a 3.7 Viscous Coupling LSD) 3) LSD Unites Came With Finned Rear Covers Additional Comments: a) Viscous Coupling LSD requires special splined half shafts - b) 84-87 R200's can be used in earlier cars, but require modifications they are not direct bolt in swapable to 240/260/280Z/280ZX's c) 84-89 R200's used a 12mm bolt in the ring gear - earlier R200 used a 10mm bolt in the ring gear, so you can not swap Gear Sets with the older R200's Edited July 11, 2019 by Miles Quote Link to comment Share on other sites More sharing options...
Twisted46 Posted July 18, 2019 Share Posted July 18, 2019 It has already been started but your transmission is going to be the deciding factor here. If you don't have an overdrive gear your cursing RPM will be very high. Quote Link to comment Share on other sites More sharing options...
Ben280 Posted July 22, 2019 Share Posted July 22, 2019 On 7/9/2019 at 1:55 PM, Miles said: How do you use the car? Daily driver? Race car? I'm back!! I use the car strictly as a race car. I used to drive it to events every once and awhile, but I've put a different transmission in it since then. On 7/9/2019 at 3:42 PM, Neverdone said: You know the diff from a 240sx doesn't just bolt up right? It's a completely different diff housing and will require lots of fab work or money for custom parts/axles. Either way, how usable your car will be for every day driving will really come down to how tall your last gear is. It depends what variety of 240sx you're talking about. R200 parts are damn near lego status. Yes the gears are housing specific, BUT the open diff s13 has the same axle spline count and length as the 240/280z R200. So you just need to make a new driveshaft and front diff mount. The rear cover will also transfer from a 280z R200 to a s13/s14 R200. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted July 22, 2019 Share Posted July 22, 2019 S12 aka 200sx, at least the turbo model came with an R200. That's where I got my 4.11 from a long time ago. I thought the center was just similar, I didn't realize they actually had long noses in the early 240sx's. Opens up some more possibilities. Quote Link to comment Share on other sites More sharing options...
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