Wheel bearing failure and diff failure related? Miata content

I'm in the process of swapping out the differential in my '90 Miata. I bought it with the diff broken. Found an used open diff, and am replacing the entire carrier assembly. When I was removing the old carrier, I noticed that the left rear wheel wouldn't rotate freely, it took both arms wrapped around it to make it turn. I figured that was caused by the bad diff. I proceeded to take the old one out and am currently bolting up the new one. While bolting the new one up, I had to rotate the wheel to be able to line up the holes from the axle (connected to the wheel) to the stub axle (connect to the diff). This was the first time I tried to spin the left rear since prior to initial disassembly. I figured that since the axle wasn't connected to anything, it would spin freely. Nope. Still took a lot of force to get the wheel to turn. E36 M3!!!

I have to take the wheel off and make sure it's not the caliper stuck or something, but I don't think it is. My guess is bad bearing? If it is a bearing, could that have been the cause of the differential failure? Would a bearing seizing up put undo stress on the diff and cause a failure? It would seem odd to have both failures at the same time.

That car was sitting for a while, get the caliper off and see how it spins then before worrying about the wheel bearings. I think I gave Jeff some extra Miata calipers if you need one. I have had to replace rear calipers on most of my Miatas as they would get stuck.

In my experience with the miata the rear wheel bearings start to make a lot of noise before they become that hard to turn. But the rear calipers tend to stick pretty easy.

Ditto that - I've even had a NA caliper seize while driving. A fix may be as easy as greasing the sliders.

Yeah, I definitely planned on taking the rotor off first, to check. Guess I'm jumping the gun. I didn't realize the Miata calipers were prone to sticking. The car has been sitting for about 6 or 7 weeks total now. Keeping my fingers crossed that's all it is. Weather is getting really warm here and I'm anxious to get it on the road.

My 91 Miata rear calipers seized up pretty easily. Try backing the adjustment bolt on the back of the caliper out and see if it is sliding freely.

Another thing they like to do is work perfectly - but the handbrake mechanism seizes up. It's easy to spot that because the cable will be a bit loose on the arm coming off the caliper, and you can usually just pull the arm back again.

Yep, I jumped the gun. The caliper needed a bit of "persuasion" to swing up once I removed the lower slider pin. But once I had it clear of the rotor, everything spun freely. The lower slider was pretty dry, haven't checked the upper. Definitely glad that at the worst, I need another caliper.

Grease te ever living snot out of the pins. If you get new calipers, still grease them, as they tend to come fairly dry.