Setting up a ring and pinion

So, I need to change out the diff in one of my cars. The replacement one I have is already set up, but has the wrong ring and pinion. I've never set one of these up before. This article on Miata.net makes it sound fairly easy, no worse than setting a set of bicycle bearings. Is it that easy? It is something I should tackle myself, armed with nothing more than a couple of measuring tools? Or should I take it to a pro and bow to his superior knowledge and ability?

So many questions. I've done just about everything else to a Miata, but never messed with gears.

I have never actually set up a ring and pinion set. I have watched it being done. On a used set I have seen techs use yellow gear marking compound, turn the R&P by hand to get the tooth contact pattern and also use a dial indicator to get the backlash BEFORE disassembling the diff. The guys in my shop have done so many they can do it by eye, but were I in your shoes I'd snap a couple of pictures of the tooth pattern.

Then disassemble and reassemble as neccessary.

The link you provided does not show anything dealing with the pinion. The correct pinion depth is what is so hard to set up. I also got a couple of generic articles on setting up a diff off the internet when I was going to do my Spitfire diff. I finally paid a professional to do it. The Miata should be easier since it adjusts the ring gear with the side adjusters. The Spit uses shims.

I'd say that since it's for the Targa, I'd let a professional that you trust do the job. Heck, they might be willing to teach you how, so that you can do it the next time.

Ask here: http://www.jeepforum.com/forum/forumdisplay.php?f=9

Nobody spends more time inside differentials than the Jeep guys.

That link assumes you'll leave the pinion in the housing and are simply swapping the differential guts out - as I am planning to do. Would it be necessary to set up the pinion depth in that case? I suppose if there's any difference in the bearing tolerances that could cause a problem.

Yes, it's for the Targa car. I've had them done professionally before. The first time, I had to have a brand new $1100 differential rebuilt after 4000 miles. The second time was lucky :) I should just take it back to those guys, but I was hoping to save a couple of hundred bucks. Oh well, it's only money...

Are you just swaping the open diff for a locker? If so you would not and should not disturb the pinion at all just the two caps and adjuster rings. Measure the back lash before you start with feeler gauges in the theeth. It's not to hard the hardest part is setting the preload and keeping the lash right. Many places just use a set number of knotches after no play is felt for the preload.

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Yes, just swapping out the differential unit. Maybe I'll have this one done professionally and try the next set myself.

There's a DVD/Video out there, i think by Paul Zank I watched it a couple of times it doesn't seem all that hard to do just takes time to setup, remove, check, repeat. I'm sure with your experience you can handle it and there's always the first time...ok maybe not when the car's going to Targa.

It's only money, but those Canadian dollars go so much further down here these days

Woodyhfd wrote: Ask here: http://www.jeepforum.com/forum/forumdisplay.php?f=9 Nobody spends more time inside differentials than the Jeep guys.

Absolutely. It was a 4x4 shop that did my Spit. He looked at it and said it was just like a Rover, which they do all the time. Most other shops wouldn't even talk to you when they heard "British car".

I'm a little confused, which is common. Your original post says you have the wrong ring and pinion, but now you say you are only changing out the diff part. It may not be too tough to do if all you are doing is changing out the diff part (sun wheel and planet gears or spider gears I assume).

Just as a caution, be aware that ring and pinion gears are a matched set. Shouldn't change one without the other. I'm sure you already knew that.

you could do it your self, then take it to the pros for inspection. If you have done buisness with that shop in the past and are in good trems with them they shouldn't mind, and probably won't charge much. They might even compliment you on your good work or offer you a job!

After doing a class at work where we tore down some sterndrives and put them back together, having to set lash, bearing preload, etc etc etc

I'd pay somebody to do it!

It wasn't super hard, but was very tedious, and you have to have a really good "feel" for what you are doing.

Here's the long story: I have three complete rear ends. Two have 4.3 ring and pinions, one has a 4.1. There are two Torsens and a Guru differential in there, with the Guru wrapped in a 4.3.

I want the Guru to be a 4.1. So I'll pull the Torsen diff out of the 4.1 R&P and stuff the Guru inside. At some point, I'll reinstall that Torsen in the now-empty 4.3. It's a pain, but that's racing. My original question wasn't well worded, but I didn't want to get into a more complex description of the little differential dance going on in my garage.

I don't do that much business with the local drivetrain shop, it's been a few years. This isn't something I have to do very often. I'll get the pros to do the Guru setup (that's the race diff) and I'll tackle the Torsen myself as it's less critical.

Sounds like a good plan and if you take enough pics and notes you can add a new project to the next version of your book which will help a lot of people out as the diffs and transmission internals are such mystery to most. I've been away from the boards for a while are you still working at FM or move back to Canada?

I think that I have have caused RussellH's confusion. That was a joke about Canadian dollars. For Keith and myself, going home is more expensive than it was a few years ago (we're for different areas of Ontario). He's still at FM.

I feel your pain. I just went through this with my SM car-

Original car was a 4.08 open diff

Installed a Torsen from a JDM S15 in that pumpkin, with the 4.08s and the S15 stub axles

Purchased an R32 diff with 4.36 gears and a factory viscous unit

Pulled S15 diff and stubs from 4.08 pumpkin, removed viscous from 4.36 box, install Torsen into 4.36 box and reinstall in S13

Sell R32 viscous unit for install in the S14 chassis with an open diff that I just sold.

Don't you love cross platform compatibility?

Still not happy with the lash, but it's the same as the factory fit. Will probably remove it and have a pro go over it at the end of the season.