Need a new diff, what are my options
 

I blew my 1.6 LSD diff. I need a new one. Local junkyards have nothing, local sellers want $1,000+ for a 1.8 swap kit. Plenty of cheap 1.6 LSD diffs on UK eBay, but none of them are willing to ship to the states.
What are my options? How much should I expect to pay for a 1.8 swap? What ratio should I look for, or should I buy a 1.6 core for around $500?

Well... In conjunction with?

How much power are you making, what is your goal with the car, which transmission are you using?

If you already killed a 1.6 diff why would you spend $500 to put another one in?

1.8 diff swap is the logical answer. $1k isn't completely out of line for a 3.9 torsen with axles and drive shaft. The desired ratio will depend on power goals and planned usage for the car.

The diff was making noises for a bit, and then they got louder, and then metal grinding noises. I only have a swapped 1.8 engine making 135/120 at the wheels. I do drive hard, I run dunlop zIII. lock and slide often. Sounds like normal use to me. I would have thought my clutch would have went first.
that $1k is a 3.90. is that what I want? do I need any other parts? probably besides bushings.

If you are drifting, you are going to need a lot of parts...eventually.

But yeah, if you are hard on it, you need the bigger diff. Period. For clutch kicks a 4.1 or 4.3 would be best, imo. You wont have the power or the need for anything taller.

I totally agree with the 4.1 or 4.3 route based on your “needs” and have personal experience with all 3. 3.9 is not a good idea at all for the 135/120 setup.

higher ratio = faster acceleration, but lower top speed, easier to break traction right? I dont drift, i just drive 7/10 when i can

You are correct. 4.3 makes it a solid break-traction setup. A 4.1 would suit you pretty good on both worlds (highway and launching).

1.6 lsd came with 4.30 only right?

Correct. The 4.10 is probably the least desirable ratio; too light for turbo guys and too heavy compared to 4.30 for stock motors. That does make them cheaper generally, if you're ok with the drawbacks. Where are you located? $500-700 would be reasonable for a 4.10/4.30 swap setup.

Im in Chicago. The only thing I see around $500 are just 1.6 cores on ebay.
junkyards that pull for you want 1000 for an entire rear NB subframe, but its 2005 and a 3.9

That is a healthy number, stock engine? Dyno?

If you are drifting a stock miata with Z3's in the rear you will definitely be breaking things, especially 1.6 things. For that power you should have plenty of grip with the typical 400tw tires people get for <$50. Make sure your rear alignment is good. a 1.8 swap is what you need, 4.1 or 4.3 for sure.

yes, that is the dyno results. bp4w with full intake and exhaust. i have no problem breaking traction when its a bit chilly. hard to on a hot summer day, so i dont often. alignment is good.
So I need to get a diff from a NB1, as that's the only 1.8 with a 4.30 ratio. What years does that cover, and did all manuals come with lsd for NB1?

pretty much all I found
https://www.ebay.com/itm/90-05-Miata...EAAOSwx1Rdo5CC

https://www.redlineautoparts.com/blo...-buyers-guide/

Time to study up. There is a lot of info out there on this topic already.

Im thinking of picking this up here. its RHD subframe. I actually need a new control arm upfront, so I think I might as well buy the whole thing. Its from a year 2000 Miata, so thats a 4.30 right? otherwise everything is the same besides power steering right?

https://www.ebay.com/itm/264481866141?ul_noapp=true

¯\_(ツ)_/¯

you do you man. I’m sure you could find someone on this board or Ebay to ship you a torsen for like half that. Control arms are $45 from rockauto.

im gonna keep looking, but so far everyone with a rear kit wants 1000-1200 for it.
1500 for an entire rear subframe, and a front subframe shipped is a nice deal when compared. is it a direct bolt up? I get NB brakes and brace mounts as an upgrade. entire thing is rust free, i can clean and treat it all. probably has better bushings than mine, its lower mileage.
yeah, im gonna buy this the more I think about it. i got bad control arm upfront, and a mangled camber bolt hole.

Yes, it will all bolt up, but the NB steering rack has a different attachment than the NA, so you will need a LHD NB rack, and a 1.8 driveshaft. You may wanna confirm with the seller what ratio that torsen is, 3.9 was available in 99 in the US, no idea what was available overseas for the different years.

Whats an easy way to verify the ratio? seller says its from a 2000 model year. all info i found is that NB1 came with 4.30

NB1 2000 SE came with a 3.9 torsen. Safe bet is if the car the diff came from had a leather interior and a 6 speed transmission then it also came with a 3.9 torsen. Unless we are talking about 2003 and up.