I have no experience with this issue
 

Gentlemen,

I did a one-day HPDE at VIR Wednesday. Everything seemed fine on track. Now, I'm doing my post-event clean up and inspection.

I generally don't start the car when she's in the garage. I pull her out and normally push her back in, just to avoid the fumes. Today I noticed it took more effort to get her out of the garage. Normally, once she gets onto the slope of the driveway, she'll keep going unless I throw a chock under a tire. Today, I literally had to pull her all the way to where I wanted her.

I got her back into the garage and checked each front corner for a stuck brake. Both fronts spin freely. I jacked up both sides of the rear together. The right rear moved easily forward and backward. Rotating it did not rotate the left wheel. The left did not move freely. I pulled the left wheel and backed off the emergency brake adjuster. The caliper slides freely in the bracket. I could not move the hub using my hands grabbing the bare lugs. It actually felt like the lugs were deflecting when I tried.

The left rear did not exhibit anything like a bad hub when I shook it with the wheel installed. When I did rotate it by hand, there were no ugly sounds. If I moved it one way, when I changed direction it moved 15-20 degrees freely before encountering resistance.

The rear is a junkyard 4.10 unit from an NA8.

Any words of wit would be greatly appreciated.

Pull left rear hub/halfshaft. If free spinning replace differential.
Sounds like trashed center section to me.
Pull diff drain plug first, might prove need all by itself and you can still move car until you get parts.

I drained the diff. The Mobil 1 looked like any other oil change. There was no glitter, and nothing out of the ordinary on the drain plug magnet.

I'll pull the half shaft in the morning.

Alrighty then... I popped the axle out of the diff and removed the axle still attached to the carrier from the car. I put a BFS between two studs and could barely turn the hub. I have a spare carrier (condition unknown) and the hub turns easily by hand. Can I assume it's a bad bearing since the wheel felt solid when I shook the mounted tire?

Thanks,

Sounds like a bad bearing to me.
Could also be an axle /hub seal interference.
Mazda deleted the inner wheel bearing seal past 2002ish (I don't know the actual vin split) and later axles will not fit well in the carriers that still have the inside seal in them.
They rip the shit out of the seals. Multiple threads on here describing this issue.
Worth looking at after you get the axle out of the hub.

If I install the spare knuckle, bearing, and hub WITHOUT the axle, can I get an accurate test of the condition of the hub?

It appears that I have one spare knuckle with a good, smooth bearing but a bad hub, and one with a good hub but a chunky bearing...

Yes and no to the question. Yes you can feel if you have a trashed bearing but you might not feel a lightly damaged bearing until it's installed and underpower with the cars weight on it. bearings usually make noise long before you can feel an issue.

Don't worry about your spares yet.
Diagnose the root issue with what is on car.
You've taken the hub/carrier and axle out of the car, correct? Just mess with those parts first.
If the removed assembly has excessive friction remove the axle from the hub and re-check

From what I've read on this forum re-using old hubs (and even new hubs) is a poor idea on a tracked car.
There was a long thread on using MR2 rear hubs on Miatas
SADfab MR2-S rear hubs for Miata - Miata Turbo Forum - Boost cars, acquire cats.
Those came from this thread
MR-S Rear Hub Discussion - Miata Turbo Forum - Boost cars, acquire cats.

If I was in your shoes I'd look closely at that thread. I may go this route with my street car.

I'd definitely look at different options.
I tried to purchase these 90 minutes after they were posted, got no reply at all from "overthetop".
V8R NA & NB Miata Rear Wheel Hub Assembly - Miata Turbo Forum - Boost cars, acquire cats.
Maybe you will have better luck.
I'd have snagged them if he replied.
I hope this is helping you...

It's certainly helping. Thanks much.

The bearing that was on the car when I posted is unquestionably bad. I have some "spares" that I know aren't perfect, but could probably get me home back when I was driving to and from events. One of those spares has a good bearing but the hub has a slight wiggle (which is why it's not still on the car). I just spent an hour with a slide hammer trying to get the hub off that knuckle. It didn't budge. My right hand looks like a catcher's mitt and my shoulder put out a Do Not Disturb sign. Fuck that guy on You Tube that gave it one wack and had it come off.

At least I'm pretty sure it's not the diff...

I have an air over hydraulic Hein-Werner 25 ton press for that type of crap.
A good machine shop should have something that will work.

Driving to and from events is one thing. Driving in the event is another.
I would not reuse a bearing or a hub on a tracked vehicle. Especially a hub with a possible issue.
I seldom reuse a hub on a street car. I never re-use a bearing. Both re-uses have way to much liability for a shop owner. The hub would have to be perfect and damned expensive before I'd re-use.
I'd get a waiver from my customer if I did re-use a hub. CYA!

4 decades back a friend and I were trying to remove a bad flange on an early Honda (first real shop job flagging hours for me) with a slide hammer.
We'd worn ourselves out to the point we could no longer feel our hands or arms. It had whipped our asses.
Another tech came by and slightly lifted the hub before he smacked it and it came apart like nothing. One strike!
Of course the response was "why didn't you come over earlier" and "Fuck you!".

There was a ridge in the hub to bearing bore that was locking it in.

Since then if I cannot get it to move in 4-5 attempts I try something different.

I'm not necessarily trying to reuse old parts but rather trying to (learn how to) complete the whole replacement process myself.

K
Pimp juice can be your friend (1/2 Dex III the old non-synthetic type and acetone)
This stuff works great on ferrous to ferrous; better than ANY penetrating oil that I've found and I've tried a bunch.
Wintergreen oil works better on dissimilar metals.
Nail polish remover is acetone. Your wife will wonder WTF when you ask her for some.
You don't need much Pimp Juice. A two ounce bottle will last me about a year. Make sure the bottle has a good cap as the acetone will evaporate quickly if left open.
It will separate quickly. Shake the piss out of it before use. It should look like Pepto-Bismol before application. It will fuck up any plastic you drip it on.
This stuff will free up badly rusted exhaust crap that would either have broken or needed a torch to remove.

I'd use pimp juice to remove the 1/2 shaft from the hub but it may not help between the hub and the bearing. I'd try it anyway

Sometimes the hub has cooked itself into the bearing and a press is the only solution. Don't kill yourself before you try this.

Biggest tip- clean the shit out of the splines in the hub and on the axle. When clean they are NOT interference fit.
Be liberal in the application of anti-seize between these two parts.
Replace the axle nut, anti-seize here as well.

I polish the hub snout (yes, even on new hubs) where it goes into the bearing with purple scotch-brite and WD40. It should feel "soft" to the touch when finished. This helps installation.
I will use WD40 between the hub and the bearing during installation, also between the carrier housing and the bearing.
I polish the inside of the carrier housing same way and WD40 during installation of the bearing into the carrier. This doesn't usually feel soft as the ID of the carrier is pretty rough anyway.
Polishing the bearing itself is useless, the bearings are 10 times harder than the hubs and carrier and I've found nothing that will change the surface smoothness.
Be careful when detailing these parts. I've sliced the shit out of my hands doing this because of a tiny sliver of metal (usually near the snap ring groove).
When you do all this the parts come apart fine 10 years down the road (or every year for a tracked car).

The original Mazda parts were put together dry and not detailed. This and years of use/corrosion makes this job a bitch to do the very first time.
One nice thing to remember is that the first time is the worst. After doing the above the second time is freaking EASY.

Oh, I don't install bearings made in China either. For a Japanese car I prefer Japan, followed by Germany, followed by USA .
"North America" usually means Mexico and Mexico DOES NOT list country of origin for anything (this is something the auto makers use to hid Chinese content). It's common for them to re-box Chinese parts and label them "America" or "North America"
The bearings themselves usually have country of origin on the dust shields.

I'd give you more poscats if I could.

Thanks much!

Great post. Props for this.

I never heard it called "pimp juice", but I use the stuff all the time.

Agree, have a cat!

Alrighty then...

I have three junk knuckles, two lefts and a right. I got the parts to make a pair of spares. I didn't buy the most expensive parts. This was an experiment. I have access to what appears to be a WWII press, possibly of Nazi origin. Breaking down the knuckles went fine. I only had one knuckle prepped for install. Pressing in the bearing went fine. Unfortunately, I pressed the hub in too far and ruined a bearing, and now I have to get the frickin' race off the hub to reinstall it...

The Shop Manual has no info on exactly how to install the hub, other than "Press the rear hub component in using the SST".. How do I know when to stop the press? It really wasn't obvious, and I had the press on full SLOW.

Thanks,

By "feel" and the sounds/movements the press makes during installation.
I can see movement between the hub and the knuckle as the hub is going in and when the movement stops I'll go a tiny bit more.
Normally I'll start seeing "load up" and flex in the arbor plate at this same time.

I have an air over hydraulic press with a gauge on it. During slip in I'll see 200-400 psi and once it's seated I'll see a significant raise in pressure on the gauge (600+)
The arbor plate will load up at this same time.

It's watching what is happening overall that tells me when to stop.
Except when you have a pressure gauge which works best...

The gauge is inop on this press. A casualty of the war I presume...

(I should have titled this thread differently.)

I now have three OEM rear hubs to play with, all in obviously used condition. None with any apparent defects, but I have no idea how many miles are on any of them. Are these usually re-used when doing a knuckle rebuild?
Thanks,