Rotating the tires and counting drive line rotations, it came up at 4 1/2:1. No one around here had ever heard of such a thing in an r180. To end a bunch of local arguments, I pulled the cover off . The numbers on the ring gear are 37 X 8, which works out at a 4.50.

Can anyone tell me from the picture what I actually do have, such as a brand name, or a type or how I can find out? (It is a 180 isn't it?) 4.5 seems pretty deep for a driver, but it will have an 83 5 speed in front of it (this is all in my 72 240 with an L28).

I am open to opinions on what I should or shouldn't do

If I had to guess I would say that it came out of a pickup truck. A 4.11 would be 37 x 9. Several people have suggested to me that I ought to pull the front differential from a 4x4 pickup truck because "they are always 4.11 difs." If you actually poke around on sites that sell Nissan truck parts you quickly discover that the "always" part isn't accurate.

I don't know what a 4.5:1 final drive ratio would be like around town, but I suspect it would be annoying on the highway. (There may be some tracks where it would be handy...)

Actually, 37/8 is 4.625. It does look R180ish, rectangular and

skinny, although it would be easier to tell with the cover on (for me anyway).

Here's a calculator you can play with. There's an 18% difference from the 83's stock 3.9 to your 4.625.

http://www.car-videos.net/tools/speedrpm.asp?Car=Select&Num1=205&Num2=70&Num3=14&AxleRatio=4.625&Ratio1=3.062&Ratio2=1.858&Ratio3=1.308&Ratio4=1&Ratio5=.773&Ratio6=&Ratio7=&Redline=6250&Increment=500&B1=Recalculate

I've got a pic of the diff cover now. If I can identify what the carrier is, the next step would be to find out what other gears I can go to. I'd really like to keep the posi as it was a "bonus" with the car. I don't have a traction problem with any of the other three Z's, but bragging rights and the cool factor and all:cool:

I don't know if the Z rear suspension responds to LS as well as the semi trailing arm rear on my old E21 323i, but if it does, you'll love it. Adding the limited slip to the 323i was one of the best things I did to that car. You may not think you have a lack of traction now, but after driving with the LSD you may learn otherwise.

I don't see too many R180's but that looks pretty narrow. It might be an R160.

It's probably an old Nissan LSD, if the cross pins look like this then that is a pretty sure bet: http://album.hybridz.org/data/500/90952way1.jpg

If it has 4 of these square shaped cross pins, it is a 4 pinion, 2 would be a 2 pinion, I think some R160's had a 3 pinion setup.

It's probably an old Nissan LSD, if the cross pins look like this then that is a pretty sure bet: http://album.hybridz.org/data/500/90952way1.jpg

If it has 4 of these square shaped cross pins, it is a 4 pinion, 2 would be a 2 pinion, I think some R160's had a 3 pinion setup.

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I had to go look. Only one cross pin that goes all the way through. I can see 4 spider gears. Bottom of the case has "4 X U" stamped on it.

IK, do you have 4 Zs, or had 4 Zs? You have four listed in your sig. At least one of your 240s should have an R180 unless you've swapped them to something else. Is this a new diff you picked up, or it came in a car, or ??? Did it come in a Z? Curious, a little background story might help.

Yes I have 4 z's that are drivers, and a parts car. 2 280's and 2 240's. I have one of the 240's on the rack and all of the suspension out so can't move it. It appeared, in just a casual observation, that the other 240 had the same appearance (differentially speaking).

The whole 240 thing is a pain. Both are 72's, both are 110 orange with white interiors. One is an auto, one is a stick, but it makes it tough to determine which car is which in conversation. So, named one Otto, and the other Manny. What's a guy to do? :classic:

The 240 that this unit came in I bought a couple of years back. It had a 260 motor in it and a 4 speed. The PO said it had a posi with 4:56 gears in it and "was set up" for the 1/4 mile. Beyond that I have no information at all. I honestly didn't think it had a posi and certianly didn't think it would have gears that deep.

I'll try to get a pic of the Otto car's rearend;) tomorrow for a reference. I was certain some of you guru's would know exactly what it was and could tell me to keep it, sell it, or chuck it. I have never driven the car so can't tell you much about how it works. Everything inside is clean, intact, and functioning as near as I can tell.

Since you have the diff open, can't you just measure the diameter of the ring gear? My understanding is that that is what the differential designation refers to. 20mm's is slightly under an inch, so it should be clear whether you have a 160 vs. 180.

By the cross pin it's a Nismo clutch LSD based on the ramp angles, sounds like a 2 pinion (2 pinion gears, 2 side gears for 4 spider gears altogether). If I'm right that the R160's had a 3 pin setup then that would be an R180, which came in 2 pin and 4 pin. Of course you should keep it. Like Arne said previously, it makes a HUGE difference in a Z car.

Remember the LSD additive when you fill it back up. Doesn't matter whether you use the Ford, GM, or Chrysler stuff, but you need something otherwise it will chatter pretty badly.

Edited January 31, 201114 yr by jmortensen

Thanks Jon. Now I am curious if it would have been oem in something from Nissan or would have been purchased over the counter. (if oem in something, I can look for another for the other car:cool:)

I found this site and thread http://www.driftworks.com/forum/technical/65994-diff-identification-help.html and specifically post #5. The picture there looks like my picture, but if I read it right, that one is a 200, thus part of my confusion.

So, I guess I will keep it, give it a shot for this car, which essentially is an in town "pretty" car. If the gears are too deep, how difficult is it to find a different ring and pinion? I am guessing that unit isn't built much anymore and parts are going to be difficult?

first pic taken from driftworks site, second is mine