ok so we are some how going to get my car to my gf's dads machine shop, hes got air tools and I assume he has a couple of BFH's.

ok got the new 1.8 in, wasnt too bad once we got the big ass bolts out of the hubs everything went pretty quick. Now I have a new problem, the diff I put in has shitty bearings. So what is that front part of the diff called, the bell(ish) shapped part that bolts to the driveshaft. Hoping maybe I can get one from one of the dudes on ebay that part out miatas and just swap it with the one I have.

So what technique did your girlfriend's dad use to get those bolts off?

actualy it was her cousin that helped me(he works at the shop) we took a grinder to my old hubs, to free the bolts from the rust

After we got them out everything else went really fast, the only other thing that took a while was getting that piece out of the bottom of the PPF, but that only took like a half hour.

So your new to you 1.8L open rear diff has bad bearings... nice. If you need a replacement center section without the carrier, let me know, I should have one from a 1996.

which part is the carrier? I dont know what all the parts are called lol at this point I think all I need is the housing with the bearings.

taking the diff apart... what needs torque and what should it be torqued to?

Does anyone sell a diff rebuild kit? One set of bearings is roast. If I can get all the bearings together that would be helpful.

is a 99 1.6 open stronger then a 90 1.6 VLSD?

so what am I supposed to start a new thread everytime I have a question? I found the bearings I need, and I got the seal I need. But I still want to know if a 99 1.6 open stronger then a 90 1.6 VLSD?

Check m.net in garage section or get a factory repair manual. 99 differential is stronger and it's 1.8 not 1.6.

The Housing.

Here is the differential section of the '00 FSM: http://www.mediafire.com/?v05w0vvcrjj

Yes. All diffs from '94-'05, Torsen or open, use the same Ring & Pinion gear design- different ratios, but the same family.

ok my gf's dad know a dude (Ted) that has several miatas. He sold me a diff from a 99. He told me that its from a 1.6, its the same size as the 1.6 that was in my 90. I also have a 1.8 diff from a 94 that will be being fixed when I get the seals in the mail. So should I put the 94 diff in or keep the 99 there? They are both open.

If it's the same size as your 1.6 open then then it's a 90-93 differential. Unless you had a 94+ 1.8 differential on your car before.

so then what does the 99 diff look like?

Externally, the 1.6 ('90-'93) and 1.8 ('94+) diff housings are very similar. The 1.8 diff is slightly longer, slightly wider, and slightly heavier, but it's really hard to tell without looking at the two side by side.

I'm not sure if I'm misunderstanding you, if you're misunderstanding Ted, or if Ted doesn't know how to count, however this line has me puzzled: "gf's dad know a dude (Ted) that has several miatas. He sold me a diff from a 99. He told me that its from a 1.6"

While European Miatas still had the 1.6 available in later years, in North America, the 1.6 was shipped from '90 to '93 only. No '99 originally delivered in in the states (or Canada) had a 1.6 drivetrain.

Now, internally, the actual differential mechanism and the Ring & Pinion gears are all pretty much interchangeable between all diffs from '90-'93, and from '94-'05, but not across those boundaries. You can put the gears from a '94 diff into an '05 housing, but you can't use the gears from a '94 in the housing of a '93, etc.

Ok Ill try to explain this better. I have a 1990 miata, blew the diff, took it out, put in a 1.8 from a 94, purchased from deliverator. Turns out the bearings were on the way out, so I got a diff from Ted for cheap since he's a friend. Was told its a 1.6 diff from a 1999. It appears to be the same size as the diff that was in my 90(I dont know how many diffs this car has been through before me.) The 1.8 that I got from deliverator is noticably bigger then the other two. I didnt put them close together but I would say the 99 and the 90 diffs are the same size if not very close. But the 99 diff is definatly not as big as the 1.8, and I used the original halfshafts and drive shaft that I had from the car.

This my my point- unless Ted imported that '99 into the US from Europe (or Japan) it did not originally come with a 1.6. For that matter, I'm not even sure that the '94+ Euro-spec 1.6 cars didn't get the later diff anyway.

Now, it's possible (though stupid) that someone may have blown the original diff in Ted's '99 and swapped in a '90-'93 diff, but it seems improbable.

Tell 'ya what-one easy way to check is to attempt to mate the diff to a propshaft. The flange on the '94+ diffs is larger. So if you have a propshaft that you know came from a '90-'93, or from a '94+, you can use it as a absolute reference.

ok it sounds like Ive got a shitty 1.6 again yay

Just saw this post, not sure how I missed it before.

Replying to point out that the diff was just fine when I sold it- the diff was "on its way out" only in the sense that icantthink ran it without gear oil in it.

Which is ironic since when I delivered the diff I gave him my spare copy of Tanner's book that contains a chapter on how to swap in a Torsen... One of the steps is, of course... add gear oil.

Still have the PM's where he admits to this.