How broken is my Miata diff? Pictures inside.

My VLSD in my '92 Miata has leaked a significant portion of its fluid out the pinion seal. I have another in my basement, so I decided to pull it apart and replace the seals as a preventative measure before replacing the one in the car, since dropping a differential is not my ideal way to spend a weekend and with my luck, I'll have to do it twice if I put it in as is.

When I pulled the drain plug, a chunk of metal came out. This led me to split the case and pull everything apart in hopes of seeing where said chunk came from - and then I found another in the case. They look like this

The ends look like they broke off something, but they don't fit together. I can't see anywhere that looks like it's missing a chunk of metal like that. The teeth on the ring gear and pinion are all good, the bearings are good, and there was very little play in the diff before I pulled it all apart. The diff came out of a running, driving car and was making no noise or odd behavior before I pulled it out.

So what gives? Is this one trash (more trash than a 1.6VLSD normally is, anyway)?

Ouch. That was why I Torsen swapped mine, to avoid that happening. When I picked it up from Expoline Automotive, the owner was asking if I raced my car, and I said yes, and explained that I launched at 4000pm on ZII Star Specs. He stopped, stared and me and just said "You play with fire". Whoops.

Are they magnets?

Side gear teeth?

oof - look like maybe tabs on the vlsd unit itself. Might be from the insides of the VLSD.

Good time to find a torsen to swap into it. The VLSD is notoriously weak. My buddy who has to run one to stay in STS collects them, I think he's got 4 right now.

Torsen is better, with better axles.

sooo, since these vlsds are apparently not really wanted, what is the going rate for one?

They're not magnets, unfortunately. This is a relatively competitive STS car, I have no desire to swap in a Torsen and go CSP.

I haven't torn into the VLSD portion itself yet. It's weird that it seemed to be working fine.

As for going rate - it depends who you buy it from. The general public just wants to get rid of them, so you should be able to find one for ~$100. Autocrossers tend to hoard them since they're a consumable.

Ack. Yeah I went to a 99+ 4.3 Torsen before this happened in mine.

I know it's 'wrong' but I'd just run the Torsen anyway. Nobody would notice and cmon... if a '99 can run STS with a bigger engine and same diff, I don't see why you shouldn't.

Blaise wrote: Ack. Yeah I went to a 99+ 4.3 Torsen before this happened in mine. I know it's 'wrong' but I'd just run the Torsen anyway. Nobody would notice and cmon... if a '99 can run STS with a bigger engine and same diff, I don't see why you shouldn't.

That sounds like my chapter. We had a season where none of the (3) STS cars were actually STS legal. My car had too wide a wheel (but not tire) and a rear subframe brace, one Miata had a Torsen swap and the 5th-gen Accord had R-compounds.

Spider gears. What usually fails first. Wheel spinning and suddenly stops.

Uh oh! Are those out of that diff you got from me? Or is that the leaking one?

In reply to WonkoTheSane:

That's the leaky one haha. I pulled this one out of the car I sold to Robbie - so he dodged this bullet.

These are all at least 24 years old, and are almost guaranteed to have some hard miles on them, so stuff like this is bound to happen.

I feel your pain man. My s2000 diff E36 M3 the bed 2 weeks ago. I wish the replacement was as cheap as yours.

https://www.youtube.com/embed/-l5tpY6SXMc

cmcgregor wrote: In reply to WonkoTheSane: That's the leaky one haha. I pulled this one out of the car I sold to Robbie - so he dodged this bullet. These are all at least 24 years old, and are almost guaranteed to have some hard miles on them, so stuff like this is bound to happen.

I guess that's the better of the two, then. I feel marginally less like a jerk :)

I've never really had sticky tires or seriously autocrossed that car, that was probably a good thing, eh?

Blaise wrote: Nobody would notice and cmon... if a '99 can run STS with a bigger engine and same diff, I don't see why you shouldn't.

Just to correct misinformation...a 99 is not STS legal at all.

Blaise wrote: Ack. Yeah I went to a 99+ 4.3 Torsen before this happened in mine. I know it's 'wrong' but I'd just run the Torsen anyway. Nobody would notice and cmon... if a '99 can run STS with a bigger engine and same diff, I don't see why you shouldn't.

Torsen has a completely different carrier than the VLSD. I mean, if anyone takes a look they would notice and the Torsen performs way better.

On the one hand, sure, at locals people don't really care that much about the details of classing, but adding a Torsen is pretty far off of some of the minor details people overlook. It specifically says, nothing other than a viscous diff is allowed in the class. A 99 is not allowed to run in STS and mechanical LSDs are not allowed in STS.

He needs to just go find another VLSD for the thing.

Redacted previous comment, I had the wrong brand in my head.

OBX diff.

358 + shipping

miataturbo install

Spinout007 wrote: Redacted previous comment, I had the wrong brand in my head. OBX diff. 358 + shipping miataturbo install

An interesting option, but if I were to change diffs, I'd just go with a Torsen. The problem with these early ones is that they're smaller - and therefore break more easily, and changing the diff itself won't change that. A stock Torsen is more or less bulletproof with stock power.

I did most of the work to pull the one that's in the car tonight, and it's also thoroughly borked - the pinion bearings are shot at the very least. So, either I buy another ancient used diff and hope for the best, or buy some setup tools and give rebuilding one a go. I might try and borrow some mics because frankly, I'm not imagining that this is something I'll want to do on a regular basis.

How much to have someone else rebuild it for you?

WonkoTheSane wrote: How much to have someone else rebuild it for you?

Good question. I have no idea - haven't looked into it at all. I'll probably just pick up another one and throw it in, it's the quickest way to get the car back on the road that I can think of. I'm missing out on all of this beautiful convertible weather.