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.

I dont have info much info on what it came from, just 2000 model year, LSD rear.
if they turn the diff by hand, can the difference between 3.9, 4.1 and 4.3 can be easily seen?

If it's a NA6 you'll need a drive shaft too.

I got a 1.8 open diff for $450 ( with axels and drive shaft ) but I had to drive almost three hours to pick up.

Turn input shaft until wheels rotate once, count how many turns the input needed to do that.
Pro: easy, fast.
Con: not totally accurate, can be hard to tell a 4.1 from a 4.3


Crack casing open, count teeth on crown, count teeth on pinion, divide crown by pinion
Pro: 100% accurate, also lets you confirm if it's an LSD while it's open
Con: you've got to pull the diff open to do it.

Any idea if the chassis number have that info attached like our VINs do?

I gave the Mazda dealer my Vin and they couldn't tell me...

AFAIK if it has power windows and leather interior, it had a torsen from the factory.

That is assuming it was from a 6-speed manual transmission car.

.....and that assuming its from the US. All or nearly all NB's in Europe came with a 4.1 diff on 5 speeds and 3.6 or 3.9 for all 6-speeds. Afaik that's also true for the many JDM NB imports driving around in the UK. We have a very hard time hunting down 4.3 ratio 1.8 diffs here because the only source is a semi-rare JDM NA8 R-package equivalent.

The only info I have is that its from a year 2000 JDM Miata.
If you call the 800 Mazda number, and give them a VIN they will tell you everything about that car. Ive been running all the local junkyard miata vins, so far everything has been auto, or 3.9. I asked the eBay seller for more info, maybe they have records of the Chassis Number that Japan uses to ID their cars.

I see a guy selling a 4.1 for $750 about 2 hours away
Found a guy selling a 1.6 LSD kit for $400
Another 1.8 4.3 core only for $750
A 4.3 Fuji set for $600

$750 for a torsen is pretty good.

The Fuji is still a LSD so that's not bad either I think.

(Make sure they come with axels and DS)

The fuji is noticeably worse in terms of power transfer. Also has that whole breaking tabs problem.

It's better than an open but I wouldn't swap one in if a torsen is available. I just swapped the tf from my 03 a few weeks ago to a torsen and it's a nice upgrade.

You can look up spec sheets.

But remember you're buying from a car that's 14 to 30 years old, so there's no guarantee that it's the same diff it left the factory with.

Should probably add.

If you're buying a Torsen, grab a T2.
Stronger since the helicals are mostly enclosed within a cast housing.

Compared to the T1 where they're held in with much less material, which can, and does, break.

(Not that i've ever broken one, but my diff builder showed me his box of busted T1s, and said he's never had a busted T2 come back)

the JDM seller had a 3.9 diff. junkyards had a 4.3, but it was stripped the day it arrived. and they wanted $800 just for the diff.

Man, i didnt think it would be so hard finding a diff for a Miata.

This guy seems to have many diffs: https://chicago.craigslist.org/nch/p...009992620.html

There's also this guy, but its a 4.10 https://chicago.craigslist.org/nch/p...009992450.html

You might just have to pay to play if you really want a 4.30

I cant find a single 4.3. already looked over all the craiglist ads from my area, and surroundings. those two ads are from the same person and he wants $900 for the 4.1 swap
some dude in florida might have a 4.3 set for $1300 + shipping
ebay i see stuff go for $1100+300 shipping or not willing ton ship

Well, one of the UK breakers has VLSDs for $265 shipped if you just wanna get rolling again.

Have you tried looking in Canada? Exchange rate difference would be worth it for you. Most torsens I see here go for 800 to 1000 cad which is around 700 usd.

$800 for a diff doesnt sound too crazy to me.

I paid $1100au (~$760usd) for my 4.1 T2 about 8 years ago. (granted, as a full unit ready to bolt it)
And that was here in Australia, where the 4.1 is dirt cheap since every NB1 came with them.


Any reason you really want a 4.3 instead of a 4.1?
it's only 5% shorter, so it's not going to be a night and day difference (hell, if you need the shorter gearing just get lower profile tyres for the little bit extra)

I cant find one. link me please. for under $300 im down to drop in a 1.6

I had a 4.3 and I liked how quick my miata was. I cant imagine it being any slower off the line. If I find a good deal on a 4.1 i'll think about it.

PM sent

Thanks for the link.
A 1999 showed up to the junkyard today. subframe gone

Another thing I'm considering. I can buy a low mileage JDM RHD front, and rear subframe delivered for $999. I can then look for an LSD, or even buy an aftermarket unit if I feel like it. I have bad front bushings, deformed camber lock plate, leaky steering rack, torn boots, worn balljoints. Car has 177k, its 1993 with an engine from a 1999, so a BP4W properly swapped using the FM kit. What will I need to change to fit that subframe? Rear goes right in. Steering rack I'm told are different between NB and NA. Which one will I need? I'm running all 1.6 accessories. How about engine mounts? Driveshaft, doesnt come with the subframe. How many variations are there? Which one will I need? I have a 5 speed. Or can a driveshaft shop convert it?
And as far as dropping the subframe. I need tips. Ive dropped subframes before, solo. But not on a Miata. I have to pull the engine right? Can I leave it in the the bay held up by a hoist? I only have jackstands to work with. And probably no help. And its gonna be a tight fit in my garage. But this is a much needed refresh for my Miata.

NA and NB subframes are a straight swap. you will need the matching steering rack for the subframe you use.
Not sure on the LHD and RHD difference though.


Mounts are same on all, except for the late NB which got mounts with an extra bit on the flange for another bolt.
But, even those blocks will fit an early mount, you just dont use the extra hole.



two versions, so far as fitment goes.
one for the 6" diff (the NA6 tiny diff)
and then a different tailshaft for all the rest of the NA/NB cars, which had the 7" diff.
you need the tailshaft that matches the diff you're using.


If you have a hoist you can drop the whole thing with the engine still attached to the subframe.

If you're working on stands, it will be far easier to jsut pull the engine all together.
Yeah, you can leave it hanging on the crane, but all you're saving yourself there is a few electrical plugs that you'll probably break anyway, and a couple of PPF bolts.
Plus then you've got to work around the engine being in the way.

I'd just pull it and save the hassle. Use the opportunity to throw some gaskets and stuff at the engine while it's out.



also, one last thing.
Is there any reason to bother swapping subframes?
Most of the stuff you mentioned (bushes, boots, etc) wont come attached to the subframes.
And most of that is much easier and cheaper to swap than the subframes anyway.

Steering rack mounts are different between LHD and RHD. You'll need to cut and weld the mounting tabs if you want to use the RHD subframe in an LHD config.

Dont forget that I will need to drain all the oil, coolant, deal with AC. My block is clean, and had a few gaskets already replaced.


Its a low mileage subframe from Japan, no rust, never seen salt. Has all the components still attached. Rotors, brakes, all bushings, and swaybars. Cars there are kept after much better than here. going with that subframe will be like taking 20 years off my car

Thanks. Is there a guide out there for this? I dont have access to a welder, but I can at least swap the rear subframe and worry about the front later.

What you are proposing is significantly more work than just swapping a diff, all with questionable results at best.

I'm 1001% sure that swapping the rear subframe as one unit is a lot easier than trying to squeeze out the diff, and spend half a day removing the axles from the hubs. Ive swapped diffs before, its always easier to drop the subframe. I'm going to drop my subframe regardless of what diff I go with. It has surface rust, and some bad bushings that I will take care of while its down.

You're just not making sense because all you wanna do is swap subframes. You don't wanna spend $1100 on a 4.3 Torsen swap setup, but you're chompin at the bit to buy a pair of used subframes for $1500, even though 1) you have no idea what gearing you'll get and 2) the front will be nearly useless to you because of being setup for a RHD NB. Not to mention it'll still be rolling on 20 year old used bushings. You keep turning down potential diffs we all mention cause they're not 4.30, but you have no idea what comes in that diff, or if its even a torsen, might be the Fuji.

????

Do what you wanna do man, you don't seem to wanna listen to anyone's advice here, despite asking for it.

Please don't think with your own wallet on this. Im not gonna drop $1100+ on JUST a diff and axles from a US seller with high mileage in unknown condition, and probably from the rust belt. For that much money I can have so much more. and yes, its more work, and more money. I am capable of both.
Front needs more work yes, but for now I can swap the rear. I ratio doesnt matter anway, that frame comes with an open diff, and I plan to swap it anyway. I can buy a 1.8 4.3 pumpkin right now for $500, So $1500 gets me a complete rear subframe (and front) in better condition than mine, upgrade to NB brakes all around, and a 1.8 4.3 diff all ready to swap in one day. That is a much better deal than the $1100 Toresn you mentioned. Or I can even buy Cusco diff, and Kia 4.77 set. That's another $2,000 I have no problem dropping right now on top of the $1000 + frame and supplies costs. So dont think with your money on this.

Rolling on 20 year old bushing as opposed to what Im rolling on now, but older, and 4x the mileage....

????

Pretty sure we are all getting hustled. OP had only 2 posts when he started this thread. I made the PM offer which he quickly counter-offered. I accepted the counter offer on Wednesday with no more comm from the OP yet he keeps this thread with a bunch of nonsense.

BTW: OP, I would have delivered and just given you the subframes in addition to the whole diff for the money we agreed to. Go pound sand.

I replied to your PM. As you can see by my posting here, I'm still researching my options.

I think that listing prices is making everyone here think hostile. Lets forget that and just break down what I want to do.
-Buy a complete subframe
-Buy a desired differential
-Install diff into subframe, and spruce things up
-Swap subframes
-Bam! rear end is done, and the car is drivable.

Front subframe remains
-Buy engine hoist
-Remove engine
-Drop subframe
-Weld new rack mounts
-Install new rack, maybe depower or go manual
-Put everything back together

More work, and for another time.
Am I omitting a critical step?

MiataOwner, I've got a 4.3 T2 I just pulled from a car I was scrapping that I do not need. I would sell it and the axles for $500 but I really don't want to mess with shipping it.

I've also got spare subframes and all the control arms, steering racks, etc that you could ever want.

We can meet halfway if you're up for a drive.
can you send me some pics and more info on the subframe you have. year, mileage.

Thanks!