I'm pricing a VLSD to replace the 3.36 R180 open diff in the car now. Any recommendations on where or where not to go would be appreciated.

Why a VLSD? It has a different spline count inside the diff than the normal R200 open or CLSD diffs, so you'll have a lot of trouble adapting it in. Check out this thread, as it explains the process in the Shortnose R200/R230 section: http://forums.hybridz.org/showthread.php?t=114798

If you're just looking for a limited slip, there is a group buy going on over at hybridz.org. R200 clutch LSD for $450 I think it was. It's a good deal. http://forums.hybridz.org/showthread.php?p=690759#post690759

I thought a viscous would be better than a clutch based on some threads I had read trying to research the difference between the two and it sounded to me like more people had problems with their clutch LSDs engaging and making noisier than usual noise while driving. After reading the post on hybridz, it sounds like a viscous is the most painful way to go in terms of parts and fabrication.

The viscous is the less racey of the two, it's passive and doesn't do anything until one wheel starts to spin. At that point the fluid in the carrier provides resistance to one wheel spinning faster than the other. The clutch style is actually torque sensitive and the harder you step on it the more it locks the two side gears together.

I haven't ever heard my clutch LSD operating, other than when the fluid gets cooked the clutches can make a whirring noise when cornering slowly. I have read about clicking from other Z owners, but it hasn't happened to me. I much prefer the clutch style, especially when consider all the BS you have to go through to use the VLSD.

Let me know if you find one in Australia as I too am after an R200 LSD 3.9 diff. At the moment I am running a 3.36 LSD R200 but want a smaller ratio so I can improve my times on the track. Good luck as I am keeping my eye out over here.

Cheers

I have the option of getting an R180 versus an R200. Pros or cons other than being able to use most of the hardware from the R180 in the car now?

R180 is lighter, you wouldn't need all the bits to swap it out. The 4 pinion R180 LSD should hold down 300 hp or so, so you'd have a ton of room to grow power wise.

The R180 changed around 1976. You'll find good gear ratios in the later years from the front end of the 720 4x4 trucks. 3.90's and 4.11's and I think 4.56's too. This later R180 will require a different LSD than your 73 would use. In the early years it's only 3.36 and 3.54s that are common, and neither of those go particularly well with your NA L28 and 5 speed combo. You'll have a theoretical top speed of 200 mph, but an engine that can't push the car faster than 145 or 150 mph.

So if you want to change the gear ratio, I'd look at the later LSD and the truck diff for the R180.

R200 is heavier and bigger than you really need, but you'd never have to worry about it. It is really too wide for the early Z suspension and you end up bottoming the halfshafts. CV conversion fixes that problem. Details at www.betamotorsports.com click on bench racing then R200 handling issues for details.

You could easily find 3.90's, and 4.11 R200s are fairly easy to come by too. You would need all the additional parts to install it, and then possibly the CV conversion.

Your choice, but with the current engine you have I'd go with the R180.

Jon, thanks for all the info, it's been an education. I called Reider and they're out of the early R180's so I will get to mull over my decision some more. I don't see the car being over 300hp so i'll probably stick with the R180 unless an R200 falls in my lap.

There's a guy on hybridz selling an R200 LSD 3.9 ratio from an Infinity J30 right now!

Jon, please tell me about the R180 3.9 LSD. I was unaware that these existed! I have the R180 3.9 from the front of a 720 4x4 truck already and would prefer an LSD unit.

There's a guy on hybridz selling an R200 LSD 3.9 ratio from an Infinity J30 right now!

Jon, please tell me about the R180 3.9 LSD. I was unaware that these existed! I have the R180 3.9 from the front of a 720 4x4 truck already and would prefer an LSD unit.

A 3.90 LSD wasn't offered from Nissan that I'm aware of, but you can put one together yourself. You would just need the later version of the R180 LSD. I think you could buy it out of that group buy right now. I seem to recall that they only have one or two R180 LSDs left, so if you wanted it you should grab it now.

I am not entirely sure of this part, so don't hold me to it. I know the difference between the early R180 and the later version is the size of the hole in the ring gear. One has a larger hole and the other has a smaller hole. I ***think*** that the later version has a larger hole. So if you tried to use the early LSD with the later gear set the ring gear would actually be loose on the carrier. It needs to fit tight, so you need to get the correct carrier to go with the correct ring and pinion.

I know that zcarnut, Steve Golik, has described in detail the differences on Hybrid Z before. I guess I should look up that old thread and then add that information into my What diff should I choose post...

The other complication that I can think of is that the later diff takes clip in axles and the earlier ones take bolt in axles. I think that problem has been solved for the open diffs, but not sure about the LSD. I don't think it would stop me though if I were running an R180...

I got it figured out. You need to be able to clip in the side stubs into the LSD. So you get some modified side stubs from www.betamotorsports.com. Then you get the later Power Brute LSD, and now you have an LSD that fits your ring gear and the side stubs that clip into it.

The earlier 180 ring gear inside diameter is 110m.m. The later (Mid `76 on) is 115m.m.

Here's the link I was looking for the other day. These are the diffs that I am aware of and why I was asking my previous question.

http://www.classiczcars.com/forums/showthread.php?s=&threadid=1568&perpage=15&pagenumber=2

I've got one of those R180 3.9 units that will be going into my car and if I can get an LSD R180 3.9 that would be even better!!