Holdfast

Im in the middle of swapping a 4.11 ring and pinion out of a 95 miata into my stock 85 lsd rear end. I need some advice from someone that has done this before. Which pinion spacer do i use? Miata or rx7? or do i need to order other spacers because its a custom combination. The spacer im referring to is the one under the rear pinion bearing. I have all new bearings and crush tube.

GSLSEforme

You will “start”with the pinion spacer from the original Miata ring and pinion and install-new bearings- and assemble differential and adjust ring gear backlash to spec and then use gear marking compound to check tooth contact pattern on ring gear and adjust shim(pack)as needed to adjust tooth contact pattern.

Mazda gearsets,carriers,chunk housings are made to much tighter tolerances than domestic diff parts.
Have done what you’re doing many times and the amount of times the original pinion shim was reinstalled under bearing and put into another chunk and diff assembled with proper backlash,the tooth contact pattern came out perfect @70% of the time.

It is likely you’ll need other shims to get proper pinion depth. You should measure the shim you’re using with a micrometer before installing under pinion bearing so you know what you’re starting with to allow calculations for shim adjustments to move pinion in/out to get correct tooth pattern as necessary.
I keep an assortment of shims on hand to minimize downtime. Keep in mind you have another shim(s) under lower pinion bearing in pinion you removed from your chunk with original gearset.
A combination of what you have mix/match wise between the two may give you what you need.

Shims are available thru Mazda dealer and they usually have a selection in stock as Mazda third members used same size parts for a lot of years.Driveline shops should have them too if they do an amount of import work.

Once you measure what you have and determine you need other shim(s),calculate thickness you need and post here or pm me and i’ll tell you Mazda part # for shim you need. Recommend getting several,both sides of what you think you’ll need so you can assemble without waiting on more ordered parts. Shims are only couple dollars apiece.

Especially since ring and pinion are used and run together previously,you must duplicate prior tooth contact as noise/premature wear will be a result.

Also use the original crush collar from the Miata gearset while setting pinion depth. Crush collars are a one time use.
I have setup bearings for lower and upper pinion bearings I use to assemble ring and pinions with to check/set pinion depth to allow easy separation of parts to adjust shimpack as needed as pressing bearings off ruins them.

Assemble diff with setup bearings,used crush collar and no pinion seal and tighten til pinion is snug in housing. Don’t worry about pinion bearing preload,you’re only trying to check pinion depth/tooth contact pattern.
Once you have desired contact pattern,disassemble diff and press new lower pinion bearing on with selected shimpack and install new pinion seal in housing and new crush collar on pinion and assemble with yoke and tighten to proper pinion bearing turning torque for new bearings. There is a different spec for used bearings.

Accept the fact to do this right,you will potentially assemble/disassemble diff several times to get tooth pattern correct. You may get lucky on 1st assembly but don’t assume that will happen.

You can make setup bearings by purchasing cheap upper and lower pinion bearings and honing out their id with a small brake caliper hone til they install on pinion with very little force.
You don’t want them to slip on with a loose fit. You want to be able to remove them easily without force that would damage a new bearing.
You’re not using cheap bearings for anything other than for their dimensions for diff setup. Dimensions on cheap and quality bearings are near identical,it’s materials they’re made from that determines the quality

You may wish to consider a crush collar eliminator in place of crush collar if using car hard/high power/autocross/road race conditions where a lot of acceleration/deceleration events occur. The crush collar will slightly further deform and pinion bearing preload goes away and premature gearset/bearing wear/noise occur.

Crush collar eliminator will give a properly set up diff assembly a much longer life under aggressive use.

peejay

I'd have just used the whole Miata pumpkin and swapped the diff into it. Saves effort setting up the gears.

Holdfast

Thanks GSLSEandme. Thats exactly the kind of info i was looking for. I was also looking into the solid spacer because the crush spacer i had removed from the rx7 was too short. Wearing out the pinion bearing and wearing just the outside edge on the ring gear. I do drive it hard and plan on track days in the future. Its pushing 200hp na, so i think im going to protect my investment by getting a solid spacer.

Holdfast

I dont think the miata pumpkin will bolt up to the rear axel of the rx7. If so all u would have to do is swap drive shaft flanges. Plus most 4.10 miata differentials are open.. No lsd. Ive seen them in other ratios 4.30 and. 3.9 torsen lsd from the 6speed . they want big bucks for those.

GSLSEforme

Crush sleeve eliminator comes with selection of shims that are used to adjust pinion bearing preload to a specific turning torque value.

peejay

It does bolt up. All Mada 7" pumpkins have the same bolt pattern.

Flange is different, yes, but on the other hand, if I remember right the spigot is the same as the '83-85 (which is also the same as 1.6 Miata) which means you just have to reclock it 45 degrees and drill new holes. If you didn't want to swap the flange.

Diff swap is suiper easy compared to setting up pinion depth, you just have to change backlash.

I've wanted to do this because it looks like an easy way to make a torque arm conversion on the 1st-gen.

j9fd3s

iTrader: (3)

the 94-97 cars are 4.10
99-05 5 speed is 4.3
and the 99-05 6 speed is 3.9.

Kenku

Dammit peejay, stop having my ideas!

Holdfast

Problem setting the pinion bearing tension. I have way too much play in the pinion. I think i got the wrong bearings from rockauto. I have timken 32207M. 32206M not sure what the M is for? The original part numbers are the same but with no "M". I cant get any tension on the pinion bearings at all. Too much slop. I compared the new and the old bearings on the bench. The 32206M and 32207M have a deeper fit in the bearing race. The cone is different.

j9fd3s

iTrader: (3)

so you are saying your crappy aftermarket junk is crappy aftermarket junk?

GSLSEforme

Not helpful. Having used Timken products often in my trade of 45+ years i have not found a pattern of quality issues with this product in use on Mazda or any other make vehicle and have substituted them for original bearings many times.

OP the M suffix in Timken bearing line denotes medium duty which is appropriate for use in your application. The part number appears to be correct for your differential. Did you observe bearing/race fit at unpackaging,compare new/old bearing/race before assembly? This is always good practice to catch a bearing/race mismatch before proceeding. I am wondering if this is what you have here. Can you clarify?

Holdfast

The bearing races and bearings have a different angle or cone shape to them. The bearings sit deeper in the race. Ive used timkem bearings for years on my car and at work ( im a mechanic at beverage plant ) Never had a issue with them. But the 32206M and 32207M i got from rockauto are made in poland and the quality sucks. They cost more than the other Timken bearings 32207 and 32206 too. If the "M" means medium duty thats bs. Im getting skf or oem now. I will try to get some pictures of the bearings to show you the difference in the bearing races.

GSLSEforme

Skf bearings every bit as good as oe Koyo. Shame you didn’t see the mismatch before assembly.
You don’t need to source Koyo bearings thru Mazda dealer and pay their markup. They can be sourced from several drivetrain shops that advertise online.

j9fd3s

iTrader: (3)

Timken used to make nice stuff, however in the 1st century they do not make anything, they just buy random stuff and put it in their box.

you also need to be careful of fake Timken and fake SKF, they exist

Holdfast

.I think the Timken name was probably bought by big corporation that doesnt give a **** about anything but the bottom line. These were genuine Timken bearings that i got. It has the hologram seal on the box. The chinese knock off everything now. Even spark plugs.

j9fd3s

iTrader: (3)

https://en.wikipedia.org/wiki/Timken_Company

Holdfast

I learned Timken is a US company. Always thought it waa japanese. SKF is Swedish always thought it was a German company and all skf bearings are made in India. Thanks Wikipedia. Makes me feel great about the skf bearings i had just ordered.

j_tso

iTrader: (2)

I'm also putting rear gears together and just checked my bearings.
The carrier side bearings are marked SKF and INDIA, but the inner pinion bearing is marked KOYO and JAPAN. The box is SKF branded but with a barcode sticker that says MADE IN JAPAN.

Holdfast

i just received my "SKF" bearings today and the quality is a lot better than the Timken. The others had real loose cages with lot of play and guess what? i have one skf pinion bearing that is a koyo made in japan. The other made in CHINA!! Still waiting on the skf diff side bearings.
Both my stock rx7 pinion and the miata 4.11 had the same size spacer 3.14 mm. So im hoping that a good thing and wont have to adjust the pinion highth. Will see. Got the races in the freezer now.

j_tso

iTrader: (2)

I just went through a pinion spacer episode this week. I'm putting together a GSL-SE rear but the ring and pinion were pitted so I used a spare 12A pumpkin and put the LSD unit into that.
I thought I had put it together years ago, but now I'm not so sure. This is my 3rd time putting a gear set together and they went together by the book the first 2 times.

On high mile gear sets the pattern on the coast side is supposed to be given higher priority so that's what I show.
I've read other people say you can't really the trust the pattern on well used gears so this all could have been a waste of time.

Below is the pattern from the spacer that (as far as I know) came with the diff. It's 7th out 14 sizes for spacers listed in the parts catalog.
It looks a little too deep (pinion too close).
I think I could have run it, but if it made noise I'd be super annoyed since pulling a diff is not my idea of fun wrenching.


The spacer that came with the GSL-SE diff measures close to the 2nd thinnest spacer.
I tried it for giggles and obviously the pattern is too shallow.


So I ordered a 3.20mm spacer that's a couple of sizes thinner, 5th out of 14.
I'll see how this runs.

Holdfast

When u have the pinion in without the diff and everything on to set the tension. I can move the pinion up and down about 1.25mm. Thats normal right?
j-toa if u want my 3.9 12a r&p you can have mine for $50 plus shipping from 94578. The weight is not a issue shipping if you use USPS medium flat rate box. Not much wear. It has little under 100k on it and i always used synthetic gear oil. I was lucky enough to find a 4.10 r&p from a low milage miata. Looks almost new.

GSLSEforme

No. Describe everything you have in place.

Holdfast

the pinion spacer (3.14mm) the 2 bearings, the crush tube that is 56mm , pinion flange, washer, and nut. No seal. I didnt torque it down completely because i knew the crush tube was already at the shortest allowable limit when i installed it with the timken bearings. The crush tube is not the original one. Its new. The original one was out of spec 55mm. Has a lot less play now with skf bearings compared to the timken bearings. I got the GSL rear end out of a 84 automatic. My car is a 85. Not aware of any difference between auto and manual rear axle housing. Both pinions look identical when side by side.

peejay

No. There needs to be preload. The purpose of the crush sleeve is to be a crushable spacer to hold the outer races apart, while at the same time allowing enough preload.

What you need to do is torque the nut down until the pinion preload is correct. This might take 300-800ft-lb of torque the first time, and 0 ft-lb the second time after the sleeve is crushed to the correct depth. It is not something you can do by rote, it is something you do by feel.

This is 100% why I have a shimmed spacer in my pinion bearings instead of a crush sleeve. It's a little more fiddly to set up the first time, but that's it. Crush sleeves are a pain in the *** and usually take more torque to set than impact guns can provide. I used to use a tool that was more or less a 8' long piece of iron bar welded to a flange in order to get enough leverage to crush a sleeve.