so I was driving my car pretty hard at auto-x last weekend and on the way home i noticed a hefty clunk coming from the rear if i kicked the clutch.

I jacked up the rear end and inspected things. Camber link seems fine, diff bushings SEEM fine. However, when turning one wheel, I get about 2 degrees of rotation before the differential "engages" and the other wheel turns.

The really interesting part is that when I turn the wheel in one direction, the other turns in the opposite direction. As far as I know, this is exactly how an open differential behaves. I THINK that I recall when I originally installed the diff (it is an '88 NA VLSD) that when one wheel was turned in one direction, the other would turn in the same direction.

So does this mean it's broken? How can you break the fluid? How can it break in such a way that it CLUNKS when engaged? Weird stuff.

If the verdict comes back as broken, what are people's thoughts about putting a miata torsen tyle LSD into the casing>?

 

How old is the LSD fuild? I'd say it's worn as hell though, not sure how you can break a viscous unless there was no fluid in there or something.

 

Umm 88's came with clutch types. Unless you bought an open diff. 89 and up turbos had viscous

 

s4 all has clutch types, s5 all had viscous type.

That clunk might be your front diff mount and not the diff at all.

 

it's highly unlikely you have an N/A viscous LSD, so few of them were sold in the US (mostly GTUs)

 

Like it was said, the NA version of the viscous LSD only came on the GTUs model from 89-90.
S4 NA cars either came with an open diff, or a clutch type LSD.
S5 NA cars other than the GTUs all came with an open diff.

To answer your question, can your diff be broken? Yes.

I've sheared the top off a Viscous LSD in my GTUs. (see attached pic) The car still ran with the diff like this, but it made a funny rythmic pulse sound while moving. Not a clunk like you described. Odds are pretty good you broke the front diff mount.

Since you asked, I swapped in a Miata Torsen after I killed the VLSD. It's been a great swap and has put up with all the abuse I can throw at it.

 

This is indeed the diff I have. An NA viscous LSD. Perhaps I got the year wrong, but I believe it was an 88.

The diff mount is fine. There is something wrong with the differential itself.

You swapped a miata torsen into the NA LSD housing? I was of the belief that the miata torsen would only fit the turbo housing? Did you use the NA stub shafts and the NA axles as well?


Since ive never opened a diff, can I ask, in your picture, that "cartridge" contains the plates and the viscous-type fluid, correct? and you just swapped that "cartridge" out for the miata torsen?

Thanks for your insight!

 

There was no VLSD in the 88 cars.

In the 88 cars, there was no VLSD.

Cars made in 88 had no VLSD.

If the differential is an 88, it is not a VLSD.

Il n'y avait aucun VLSD en 1988.

1988 gab es keine VLSD.

No había VLSD en el coche 88.

88車にVLSDがなかった。

 

well thats good, you have confirmed that I was unsure of the year

 

Yes, the Miata Torrsen Diff is a direct fit for NA RX-7's, NOT Turbos.

If you go with the Torsen, you need to find the stub shafts that go with the Torsen, or use 86-88 equal length stub shafts. The ones from the 89-90 VLSD will not fit with the Miata Torsen.

The carrier, or "cartridge" as you called it, is one unit. It has two replaceable bearings on the sides, and the ring gear attaches to it.

The easyest way to make sure you get everything you need is to buy the entire Miata rear diff. This way you get the bearings, the carrier, and the stub shafts that you need for the swap. You will be REUSING your existing ring gear and pinion. You're also going to need to school yourself on setting backlash, preload, and propper spacing. If you're not comfortable following the FSM, take both rear diffs to a trusted mechanic and have them do the work for you.

 

LOL, now i know how to say it in japanese!