Shaun,
where did you get your lsd ,, Is it true that it is a direct bolt in from a z31 and does it only come in a ss model. I have heard mixed views on it and will be needing one really bad soon !!!!!

 

In fact you do NOT want the SS model diff. Here's a breakdown:

* 1984-1986 and early production 1987 300ZXT's had open diffs
* 1987 there was a midyear change when a clutch-style LSD was offered in the 300ZXT
* 1988-1989 all "normal" turbo 300ZXT's should have the clutch-type LSD
* The "SS", "Special Edition", "Shiro Special", whatever you want to call them, 300ZX Turbos that were pearl white: these had a viscous LSD and it's not what you want. It's still an R200 and you can bolt the diff into your R200 carrier or put the whole case in your 280Z, BUT your halfshaft splines will not match. You could probably have shafts modified or made to fit, but the differential is inferior in most respects to a normal clutch-type and you'll probably end up spending enough that you could have just bought a new NISMO unit that fit in the first place.

By comparison, the clutch-type LSD has the same splines as the early Zcar R200, so you can use original Z stub shafts and halfshafts. In addition, the clutch-type LSD is easier to identify because it positively locks the shafts together when you're looking at it outside the car (if you put a bar on both stubs for leverage you would be able to get them to "break loose", but the axles would basically spin the same way unlike an open diff where they spin opposite). I'm not sure what a viscous unit would do, I never had axles in the one I was momentarily stuck with

I'm very happy with my 300XZT clutch-type differential, I actually installed the differential unit into my original R200 case (along with the 3.7 ring and pinion). You'll have to use the 3.7 gearset unless you can find a mid-80's or later ring gear because the bolts in the ring gear are different sizes between the early and later R200s. Alternately, you can make spacers to use an earlier gear on the LSD. If the differential is worn out you can still get parts for it through NISMO I think, or you can just get some shims from them to make a good unit tighter

Tell me if I've missed anything you wanted to know...but basically, jack up a 300ZXT and check that the wheels spin the same way!


--note: I forgot: the only thing keeping the diff from being a direct bolt-in is that the case has a finned aluminum cover that won't fit an early Z without modification. However, slap on the cover from your stock diff and you're ready to go!

 

Wow! Dr. Barrett has spoken.

This thread doesn't apply to me, but I'm impressed man!

 

That was the answer I was hoping to get and I will have to start looking very hard to find one... thanks

 

I got one NA NA NA BOO BOO!

Just poking fun at you! Shaun is correct you need an 87-89 turbo rear. OR you can keep yours and get a locker. I will have to check into it but either Detroit or E-Z Locker makes one that will work in our diffs.

 

I have a 240Z and wouldn't mind having a LSD on my Z. Are the gear ratios going to be different than the stock R180 I have in my Z now? If they are different, does this mean I can only go so fast in each gear, or does that have to do with my transmission? I would do a switch for better traction and handling in corners, but I would still want to retain the driveability I have now.

 

Your differential gear ratios are determined by the ring gear and pinion gear installed on the differential, and these can be kept the same or changed independently of doing a limited slip swap. If you changed the differential gear ratio it would have an effect on how fast you go at any given engine speed, economy, etc. just like changing the sidewall height of your rear tires, for example. You could move to a higher numerical ring and pinion set and get a 5-speed to maintain similar cruising characteristics while getting the benefit of the acceleration boost, but that's an extra shift you have to consider, too.
Meanwhile, the LSD is a separate modification, though if you were going to change your gear ratio doing them together would save time. The LSD doesn't make the car handle better per se, but it does prevent one tire from spinning freely in the middle of the corner, hurting your ability to put down power when coming out of a turn for example. Nissan Comp (and maybe Motorsport?) sells an R180 LSD unit for something like $800 and possibly some alternate gear ratios as well, or you could move to the stronger, heavier R200 and have the same cost for a new LSD through Nissan or the used 300ZXT unit to hunt up. Subaru WRX STi's also have R180's in the rear and I believe those are LSD as well, but whether or not the 240Z halfshafts would mate is anyone's guess...it might be a while before those get cheap enough on the used market to play with anyway.
http://www.reiderracing.com/pgpowerbrute.htm - here's another source of new R180 and R200 differentials. The R200 unit shown there requires 12mm ring gear bolts which means you'd have to find a later R200 gearset than came in 240-280Z(X) because they all have 10mm ring gear bolts. I think those diffs cost less than Nismo's, like $525 or something. [edit] according to 4x4 sites, the PG lsd shown there is the same unit as what's sold by the factory, just cheaper...but they're hard to find in-stock.