DNMakinson

iTrader: (3)

In addition to changing the differential ratio, you may consider:

This if you are using EBC with MS

And, the thought that you do not have to use all the gears, every time. I sometimes go 1, 2, 5. 2nd takes me to 55mph, which may well be speed limit, then row right up to cruising (I have a 5-speed). I also often skip just 4th, depending on how traffic is accelerating.

DNM

hks_kansei

My understanding was that the SE/MSM diff used the same 7inch Ring gear as the rest of the NA8/NB diffs.
But as mentioned, it had thicker half shafts, and a different diff centre to suit them (the diff centre may appear larger, but it's the crown/ring gear and pinion that's the important part)


Also look into the Mazda B series/Ford Courier ute diffs.
I can't remember if they used the 6.5in or 7in diff, but pretty sure they often came with taller ratios than the MX5/Miata, so they might be an option to grab cheaper gears (you'll need to confirm yourself that they have the same gear centrelines etc)

Mudflap

DNM I've definitely got the boost by gear setup and it is a lifesaver. That and the boost by throttle position together and it excellent. It is a must in my mind.

I've got a 3.63 ring and pinion that is slightly worn and I've got all the bearings and gasket coming in the mail. So my next move it to try the swap myself. I'm searching for a shop to handle the swap, but 5 phone calls in, and no one really wants to do it. It is funny how often that is true these days. I had a hell of a time getting all the various shops for my engine rebuild machining work.

hks_kansei

Slightly worn should be fine, assuming the crown and pinion are a matched pair (ie: both came from the same diff)
If so, they'll have worn together, so should be fine (assuming it want whining in the original diff)


As far as doing it at home, gaskets are easy.
Crown and pinion swap, less so, but certainly not impossible, it's mostly just slow annoying work setting the lash and crap.

You'll need a decent dial gauge to properly set the backlash, and from memory a micrometer.
a press is pretty much a must have too, since the pinion wont want to move without it

Plus the usual degreaser and loctite to clean it, and make sure the bolts don't shift over time.

(you probably know all that already, since if you're looking to DIY you've probably read up on it already)




edit:
if you havent ordered them, try and replace the bearings too, especially the pinion ones. They sometimes get damaged in the removal process, and saves you a headache later on once it's all bolted back up.

themonkeyman

Having done a diff rebuild and regear in my basement, it’s not that bad. The pinion shim that is on the current 4.10 pinion should be reused with the new 3.63 gear set, the logic being that the bearings are ground to extremely tight tolerances as are the gears, while the cast housings have some more variance. So keeping the pinion shim wed to the housing (not the old pinion) keeps the engagement pattern consistent. I found this to be true with mine. Is that clear as mud?

PM me if you have questions. My diff has ~12,000 trouble free miles on it and has seen...illegal speeds shall we say.

I also bought a massive 7-8” micrometer for setting the carrier side bearing preload, you’re welcome to borrow it for the cost of shipping to and fro.

Mudflap

Thanks for the advice guys. I can get the micrometer from work. I did finally find a shop willing to look at it. They quoted somewhere around $300 to do the work. So if they look it all over and feel good about it, I'm going to pull the trigger on that option. As much as I like doing the work myself, without a press, various gear pullers or experience, I fear putting this much HP into it just to damage it all.

themonkeyman

Yeah, $300 is decent, especially if that includes pressing all new bearings. You can reuse your pinion bearing crush sleeve, but a new one would be a good idea. Or for proper bulletproofing you could get a solid pinion spacer from Weir Performance. Gotta call em though, theyre not much for email.

sixshooter

iTrader: (12)

I went to a guy well-known in Jeep circles who did lots of ring and pinion set ups and he did a very nice job.

shuiend

iTrader: (24)

I paid a little over $200 to have a local spec miata shop do in mine. So your price for install is not out of line.

hks_kansei

This is always a good option.
4x4 guys and drag racers are always blowing diffs apart, so most shops that do work for them will usually have decent diff skills.



The $300 sounds ok if you're bringing them a fully assembled diff and getting the C&P swapped.
I think the assembly for my diff was about $150au when it was done, but all the shop needed to do was put it together since the housing/centre/C&P were already separated.

Bs_nb1

You can buy a 3.63 ring and pinion from mazda for $500 i beileve

shuiend

iTrader: (24)

Then you have to pay $200-$300 to have someone install it. The ones from the UK are already in the housing so you just have to swap the diff out for your old one.

Newaza

Hey Mudflap you mentioned in another thread recently getting a dragy. Did you get a chance to test with that before pulling apart differential? If so were you able to get any validated data?

Mudflap

interesting idea. Main problem is the temps. It is hard to get heat into the tires and i just spin like mad. Thus the 3.63 swap..

Mudflap

I'm back looking for more advice. Really just a shoulder to cry on.

I got a reputable shop to install some used 3.63 gears I bought into my MSM diff. I bought all new bearings, seals, crush washer etc. Got it in today and it has a horrendous whine.

1st gear, no whine. 2nd gear and up the whine gets really loud and 4 gear it sounds like it is going to self destruct.

So now I have to decide.

1. Could it be something in the installation. Anything I can check?
2. Buy new 3.63 gears ($700) and get the same shop to install those ($400).
3. Consider other possibilities? 8.8? Put the money towards a BMW arrangement?

This is painful. I'm $1000 in and have a large red paperweight in my garage..

curly

iTrader: (25)

check preload and back lash as a start. If it's not right, give it back to them. You just need some harbor freight 12" digital calipers, and a dial indicator on a mag base.

Mudflap

Update: I paid a local shop to put in my used 3.63 gear set and it whined like a third grader on the way to the dentist. So I pulled it, found it to have way too much lash, tightened it up, put it back in and WHINE WHINE. Terrible noises. So the gearset is a bust.

So I now want to push the easy button. Someone help me find that button please. I want to ship it to someone who knows what they are doing (nobody in the Colorado front range area knows how to do the swap?) and use all new parts.

Lesson learned so far: $250 used gears + $250 misc bearings, washers, etc + $400 labor = useless paperweight.

QUESTION: Would you go with the 3.308 MFactory set or the 3.63 Mazda set? I would be happy if they 3.3 is a good choice, but I certainly do not want to end up with a noisy *** end (again).

Ted75zcar

iTrader: (2)

Once this Covid business is over you can come and listen to a 3.308

Newaza

Well that bites. Any chance to get something back fro the seller for selling worn out gears if they are in fact worn that badly? What are you mainly using this car for? Street, drag, track or combination of all?

sixshooter

iTrader: (12)

Find a guy who sets up diffs for jeeps and rock crawlers like I did, maybe. Someone who only does diffs all day will do better than someone who knows how but only does a couple a year. My used 3.63s are quiet.