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Differential Swap

This is a discussion on Differential Swap within the Engine and Drivetrain (S30) forums, part of the 1st Generation Z (S30) category; My r180 differential is dying, it has a bad whining sound, and I need to replace it. So, I've been ...


  1. #1
    Z lover Pir0San's Avatar
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    Default Differential Swap

    My r180 differential is dying, it has a bad whining sound, and I need to replace it. So, I've been lurking around the internet and reading up on some articles about the r180 to r200 swap, most notably the r200 lsd swap from an 4/87-89 300zx (non-SS). I see that it's a pretty straightforward swap, but I still feel like I'm forgetting something.

    So far, I understand that you need:
    1. R200 differential
    2. Mustache bar from a 280Z with R200
    3. Stub shafts from 280Z R200 (also called companion flanges?)
    4. Half shafts from 280Z with R200
    5. Pinion Flange from 280Z R200
    6. Smooth rear cover from 280Z R200

    With all of the right parts, It all seems like a pretty easy swap. The pinion flange needs to be removed from the 300ZX LSD R200 and swapped with the pinion flange from the 280Z R200 to fit the 240Z driveshaft. The stub shafts are easy to replace, they are snap in, so you can pull on them and pop them out, and then pop the 280Z R200 stub shafts in. From there, the half shafts from the 280Z are a direct swap into the 240Z, but the drivers side half shaft needs to stay on the drivers side due to length differences and differential offset. Rear cover and mustache bar need to be installed accordingly.

    So, does that seem right? I've read jmortensen's sticky on HybridZ about the Z differentials, but I wanted to make sure I had everything clear. I did read on the Beta Motorsports page that the R200 swap could yield some binding issues when swapped into the 240Z. The only answer I have seen to remedy this is to buy custom CV adapters from Modern Motorsports and swap out to Z31T CV Shafts. Some other websites claim that by switching to 280Z stub shafts and 280Z halfshafts that all binding issues are gone...but none of them seem to have proof to back their claims up.

    I also have another concern, and that is the effect of the gear ratio on my final top speed. Right now, my 240Z has the stock 3.364 gears and stock four speed gearbox, which yield 3388 rpm at 80 mph in 4th. If I were to swap up to 3.9 gears, my rpm at 80 mph in 4th would be 3928 rpm, a difference of almost 600 rpm. This doesn't seem like alot, but I don't want to be revving the motor to the moon when driving long distances.

    Sorry if it seems like I'm just beating a dead horse, but I just want to make sure I understand everything as clearly as possible. It seems like there are tons of sources on how to get started with the R200 swap, but not very many writeups on how to do the swap successfully. If I were able to get all the information I need to do this right, I would be more than willing to make a detailed writeup, but the problem is understanding before doing.

    Here are the links that I have used for some of my info. A special thanks to jmortensen for doing his writeup on HybridZ, without it I would have no idea where to start.

    Links:
    jmortensen's differential writeup on HybridZ.org
    Modern Motorsports CV adapters
    Transmission Calculator
    ZHome reference for different Z differentials
    Slight swap info/writeup with swap to CV Shafts
    Beta Motorsports writeup on R200 Handling Issues
    Last edited by Pir0San; 05-20-2007 at 03:51 AM.
    -Jeremy
    '72 Datsun 240Z

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    Default

    Hey, you're welcome, glad you're putting that info to good use!

    The thing about the 280Z halfshafts being shorter is bogus. I was convinced that the 280 shafts were shorter until John Coffey challenged me on it. I checked it out, and all of the Nissan halfshafts that I found were the same length. That includes 240, 280, 280ZX, and 510 halfshafts. Yep, even the 510 has the same halfshafts as a 280Z. There are probably some other cars running around with the same shafts too, 200SX, etc.

    The shafts work in the 280 because the 280 sits a lot higher in the rear than the 240. The struts are an inch taller and the insulators are also an inch taller, both of these change the angle that the halfshaft sits at. They basically end up pointing the halfshaft down from the inside to the outside, and this means you need a longer halfshaft.

    There is a way to shorten the shaft. I thinkTom (240ZX) has done this, and I had it all figured out before I said screw it and bought CV's instead. Basically it requires disassembling the halfshaft and cutting the inner part of the shaft down 1". There is an outside snapring that holds the "ball bearing stop" on the end of the shaft. I think Tom had the groove for that stop machined on the end of the shaft. I was going to tack weld the stop onto the end of the shaft. The shaft is hardened so I think it would be a bitch to machine. I'm convinced that a little tack weld that would be sufficient to hold the end on would not mess with the temper of the shaft.

    I know I had a thread about that procedure on Hybrid Z about 3 or 4 years ago. You might find it or a later one where I rehashed the procedure for someone else. I know it has come up a couple times and I think I gave my procedure and Tom gave his on a couple of those threads.

    If you want more help on that, PM me. It's not too difficult and I may have some old pics of the halfshaft disassembled somewhere...

    EDIT--The 300ZXT has 3.70 gears, and they will be a bit on the revvy side with a 4 speed, and to truly appreciate the benefit I think you need a 5 speed. A ZX 5 speed with a 3.90 or 4.11 would be the ticket I think.

    I think you have everything else covered.
    Last edited by jmortensen; 05-20-2007 at 12:36 PM.
    Jon

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    Ah, thanks for the insight Jon. It sounds like the R200 LSD swap takes a little bit more work than some junkyard searching. If you do have the pics for the halfshaft modification, I'd like to see them, just as a reference. I'm looking to do it all on the cheap, so it looks like an R200 may not be the way to go.

    On the other hand, I did notice that the Auto 240-280z's had the 3.545 R180, along with a few of the Auto ZX's. I'm assuming that the swap would be a bolt in procedure, or do the stub shafts have a different bolt pattern and spline count?

    I'm looking to increase acceleration, and I'm guessing that the jump from the 3.364 gearing to the lower 3.545 gearing might make a slight noticeable difference, or will it be too minuscule to even notice?

    I'd still like to go for the R200 swap, but if it'd be easier/cheaper to drop in a Power Brute R180 LSD Carrier for $500, then that might just be the route I take.
    Last edited by Pir0San; 05-20-2007 at 01:12 PM.
    -Jeremy
    '72 Datsun 240Z

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    Default

    You would definitely notice the change from 3.36 to 3.54s and that would be a step in the right direction from stock in my opinion, but to really get the full benefit the 5 speed is a good idea, and you can run deeper gears. More torque multiplication and closer gear ratios (for NA L engines) = more acceleration. I'm using a 280ZX NA 5 speed with 4.11 gears, 3.90s would work well too.


    So here is the halfshaft. The bottom part is the inner, and what stops the compression of the shaft is when the inner part bottoms inside the outer part. By hacking off 1" off the end of the shaft you can get it to compress farther. The ball bearings and plastic spacers ride in 4 grooves on the shaft, and then the thing on the left is the ball bearing stop. I was going to cut the shaft with a band saw and then just weld the bearing stop onto the end of the shaft around the ID of it's center hole. Assemble the shaft in the normal way and that's it.
    Jon

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    Well that definitely gives me more to think about. I was considering the 5 speed swap, but didn't think it would make that much of a difference. I'll have to look around and see if I could find a good condition one at a junkyard.
    -Jeremy
    '72 Datsun 240Z

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