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HybridZ

R180 3.9


Perry G

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Hey ,

No US Nissan 720 has ever had a 3.90 ft diff . 79-82 4x4 have 4.38 and the 83 on up have 4.11....

The 810's had a 3.70 R-180 ... The 3.90 for the 81-83 Zx's is the way to go depending on what car your putting this in. I have a customer 3.90 LSD in the shop now for complete refreshing that he is using in CVAR. If your racing and need a 4.38 I have a couple open units that are being refreshed in a few weeks for sale. LSD units are hard to com by .The Suby unit works with some USA made stubs,but have never worked with that unit. Just the smaller R-160 in 510's ,etc.... I'm doing an upgrade to a 79 slick top ZX that has a 3.36 (gag) R-180 in it now. We are putting the R-200 3.70 from an 1980 model in it.

Steve

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You're talking about the r200 from the zx? I'm trying to avoid having to swap all the stuff required. It's 73 240z I'm trying to retain as much originality as possible. I have found one open 3.9 r180 out of Cali which is $500 and no clue on shipping. I was just wanting to find something I could, worst case scenario, take the gears from and swap into my diff I have now. The ring and pinion gear sets are NLA from Nissan or aftermarket.

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I swapped a subie r180 with the stubs in my 240z. Ended up cositng about $900, $400 for stubs and $500 for the lsd diff.

 

If you got with a front diff from a 720, it'll be open, but will probably cost like $200. I've found 4 in junkyards and have never paid more than $80 for one. 

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On a Zx there isn't anything to change in this swap other than installing the Only available rear mt that goes bad and is now the only available part for the R-200 for a ZX .

 

 In a 240 depending on the year the R-200 was the best and had been the most plentiful used Nissan Diff available in 3.90. Only on the 70 and 71 to relocate the diff to the late preferred position mounting do you need a mustache bar and rear suspension curved joiner link . 72 and 73 cars should be a bolt in as they have these parts we need and use for early cars. 

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Oh wow. So what about the halfshafts? Or CVs? Would my bolt on 240 halfshafts work? I guess I can just reading up on the r200 swap. All the posts I had been reading never clarified that the early models required all the different things to swap. I was planning on doing a 5 speed swap as well so that would be easy to take the driveshaft and everything from 1 donor car.

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As long as you have flange type Half shafts ,everything s a bolt it ,including the drive shaft flange. Early cars had a straight not curved rear suspension connector link.

The diff was a few inches forward in the car and cleared the rear cover. However when they found severe drive line vibration with the angled back half shaft ,especially on lowered cars ,and race cars especially ,that made Nissan relocate the diff back a couple inches to straighten the half shaft geometry out of the diff. but required the curved link to clear the rear cover. That also caused the mustache to be turned around but is also has a curve to it also. Your car is ready to accept what ever Z diff you want to install .

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Thank you for clearing up all this info for me. I hadn't seen anywhere that i could just swap it straight in, everything i was reading I guess was the earlier models. I actually have an old spare r200 with driveshaft in my shed I'm going to find out what the gear ratio is. Thanks for all the help I really appreciate it.

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  • 5 months later...

There's actually quite a story to why the early cars had  the differential farther forward and angled half-shafts. According to Hitoshi Uemura, who was deeply involved in engineering the 240Z, the diff was originally further back and the fuel tank was 70 liters (18.5 gallons). At the time there was no rear end crash safety standard but the US was considering one, so the engineers did a crash test and were horrified. The fuel tan was pushed into the rear suspension and differential and spewed "fuel" everywhere. In response they moved the diff forward 20 mm (0.79"), reduced the fuel tank to 60 liters (15.85 gallons), increased the tension on the fuel tank straps, and added a stopper to keep the tank from moving. So be aware that, in moving the diff back, we are compromising safety in a rear-end collision.

 

This information is in Uemura's book, "Datsun 240Z Engineering Development."

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