We're talking about the bolt circled in white, correct?

I'm at work but will check again when I get home.

 

Nope. The fastener below the 2 nuts with the red squares. To be fair, it isn't a bolt. It's a stud.

That's what holds up the diff housing though

 

I was looking for bolts. I have those nuts. Which sparks two questions. Why don't I have those bolts I circled in white (assuming I really didn't miss them)? And... if those 17mm nuts have to be removed, why are the bushings so hard to remove/replace?

Thanks,

 

I don't recall dealing with the bolt you circled but it's been a while for me. Might not be oem.

The bushings are press fit in to the housing with a metal collar around their OD. They are indeed a pain in the ***.

 

That pic in Post #21 doesn't even look like the rear in my sh!tbox '90. It looks to me like the differential ends where I circled the bolt. Neither of my Miatas look like that.

 

It takes less time to do this job than the amount of time we've collectively spent trying to explain it. Just watch a video.

 

I'm quoting the photo just to highlight this: that is not a stock Miata diff. It's a Getrag conversion. I don't know why someone posted it in this thread.

The large nuts on the main diff studs are in the same place as that photo, but everything on the left half of the photo is completely non-standard.

 

Agreed. Seemed like just a few easy questions... My concern was more about whether or not there is a difference between the NB1 and NA8 diffs, and that pic just raised more questions.

 

The biggest difference will be the axles, however either set will work with either diff. So you're likely best off to leave the respective axles in the respective car and move the halfshafts over to the diff going back into the NA.

 

My apologies if I created more confusion..I just googled miata diff mount to get the photo and didn't really look at the rest of the photo, I just saw the mount with the red circles and attached it so you could get a visual. My bad.

 

No worries. I'm just glad I'm not completely blind...

 

I'm the OP.

I ended up buying a 4.10 Torsen. My 4.30 developed another front seal leak and would not have been a fair trade.

I did the work with the car on jack stands in my garage.

Unfortunately, most of the videos appear to be of people who are chronicling their first adventures into diff removal, rather than being real how-to videos. Most are not helpful at all about getting the diff out of the PPF. In one, the diff is magically out of the car after removing the axles and unbolting it from the frame, and the PPF looks like it was pried open. The best one was simply a guy who seemed to know what he was doing, talking his way through it, but there was no actual "video" of the process. Understanding how to separate the diff from the PPF is the key. Although one video talked to hammering out the pressed in nuts at the top of the PPF, it made no mention of working out the locator/spacer for the reamer bolt at the bottom. No video referenced the Shop Manual, which by the way, has a black "X" superimposed on knocking out those upper pressed in nuts.

I did not remove the PPF. I popped the axles out of the diff and removed the axle/knuckle/hub as a unit. There just isn't enough room under the car to do it otherwise with it just up on jack stands. Plus, I was doing the job by myself. I had the diff out in 2+25. My only prior experience was popping out the passenger side axle to replace the seal, and removing the propeller shaft a bunch of times. I hadn't done any prep work. I didn't even have any gear oil. In about nine hours total I had replaced the diff, replaced the gear oil in the trans, swapped in a yellow gear for the trans speed sensor, and gotten the mid pipe back in place. I still need to tighten up the exhaust and put the frame brace back on.

It wasn't as hard as I thought it would be, but I believe I could do it again in significantly less time.

Thanks for all the inputs.

 

The OEM workshop manual, while a great resource, does have a lot of weird notes that aren't 100% needed.


Like how according to it, once the splined nuts are removed from the PPF the entire thing needs to be replaced (which is total BS)