www.RX7fb.com

Apart from ship over a GSL-SE limited slip diff from the States, the other option is to fit a LSD from a MX5... does anyone have the lowdown on these?
Which model years of MX5 do they come out of?
Do they go straight into the axle or need machining of the diff or driveshafts??
Do they fit only s3 axles or s1 & s2 as well?
Which is better for road use, torsen or clutch type?

I can tell you a little about mx5 diffs.

The 89-93 1.6l cars came with a 6" diameter ring gear diff. This was available as open or as a viscous limited slip diff. The 6" diameter diffs are known to break with aggressive use even at stock 115hp power and most of the viscous ones have effectivly reverted to open with 20 years of driving on them.

In 1994 Mazda changed to the 1.8 engine, and to a 7" diameter diff. These were available in open and Torsen limited slip varieties. This 7" diff handles 250hp from turbo piston engines pretty reliably.

The Torsens are mostly found in the higher spec uk models, such as the 1.8iS, and imports. the 1994 and 1995 cars were fitted with a 'type 1' Torsen diff, which has a more aggressive lock up compared with the 'type 2' fitted to 1996-2005 cars.

The mk3 uses a different diff I believe, probably similar to rx8 seeing as so much of the rest of the car is!

AFAIK, and this is only what I've read, but the 7" diameter Torsen diffs are 'plug and play' as it were into the s3 axel, the standard s3 driveshafts should fit up into the diff and everything is easy. The s2 has the same size diff, but a different number of splines on the drive shafts.

Here's a not very well written, but handy guide to spotting the mx5 diff variants. http://www.miata.net/garage/diffguide/index.html

thanks Steve, that's a great guide to MX5 diffs.... I didn't know there were so many variants!
I'm thinking it might be a good idea to go with a posi-traction rear end but only want to do it the once so need to suss it out properly 1st.

ian65 wrote:Which is better for road use, torson or clutch type?

It is a long time ago, but as I remember it the "better" type of diff depends on what you want to do with the car.....

For absolute grip in a straight line, in any conditions, it is the Torsen. It is just a cleverer diff with a smoother, graduated transition of power delivery. This is the diff you want for mud and snow and desert to avoid getting stuck.... (and maybe for drag racing... never done that...)

To stop the inside rear wheel spinning on a bend and get the power down smoothly and without oversteer, the Torsen again.

However, to "get the back end out", as in drifting or loose surface rallying, the clutch type diffs locked up faster and harder, turning your diff into a "locked" diff sooner and more predictably, which is actually what you wanted/needed for controllable sliding. Much more fun.

In the good old days the Torsens were more expensive and used by people who wanted to win. Hooligans like me couldn't afford them and preferred going everywhere sideways anyway.

John

Steve-A wrote:
The s2 has the same size diff, but a different number of splines on the drive shafts.

Any suggestions what I coiuld do for Miss January? She is an S2 and I would love an LSD but I want to stay "standard" with 13" wheels etc. so I can't go to an S3 axle. Anybody heard of a kit? Anything in Australia/New Zealand?

John

The NA S4 FC had a clutch type diff that will fit - 26 spline same as the S3.

The S1 and S2 were 24 Spline, but are interchangeable with all the early RX stuff, pity that it is all so rare!

I looked into this a while ago too - the 94-97 1.8 Diff will bolt straight into a S3 housing. They come up on ebay every so often for between £200 and £400.

I was toying with the idea myself but not sure if it will handle the power and if I would just be chucking the cash away. My best bet is a clutch type for, but they rare over here - plenty in US/Oz/NZ and Japan.

I can tell you that in the mx5 world the guys blow the gearboxes at 270-300hp before they blow those 7" Torsen diffs. I guess it depends how much power you're looking to put down

RamoNZ wrote:The NA S4 FC had a clutch type diff that will fit - 26 spline same as the S3. The S1 and S2 were 24 Spline.

Back on my favorite subject again. Any idea if there is any other difference between S2 and S3 driveshafts ie. apart from number of splines? Is the diff housing the same size? In other words, could we put an S3 diff and driveshafts into an S2 Axle?

As I understand it the overall track was the same between S2's and S3's, the suspension mounts are all the same, Just the hubs and brakes we different (and of course the Diff and driveshafts...)

John

Johnnyboy wrote:

RamoNZ wrote:The NA S4 FC had a clutch type diff that will fit - 26 spline same as the S3. The S1 and S2 were 24 Spline.

Back on my favorite subject again. Any idea if there is any other difference between S2 and S3 driveshafts ie. apart from number of splines? Is the diff housing the same size? In other words, could we put an S3 diff and driveshafts into an S2 Axle?

As I understand it the overall track was the same between S2's and S3's, the suspension mounts are all the same, Just the hubs and brakes we different (and of course the Diff and driveshafts...)

John

i've just asked a similar question on MRC.... the lads with KIMI have a hole in their diff housing and it leaks oil.... I have a spare S3 axle and wondered if they could just transfer all the s2 stuff into the s3 axle casing...
Thinking about it though...

* the brake mounting points on the s3 axle are for the larger s3 brakes... I doubt whether an s2 brake carrier would fit and you can't use s3 brakes with the standard s2 wheel... dunno about the Elford sonic wheel though

* Would an s2 driveshaft seal fit the s3 axle casing?

* Didn't Mazda change the position of the rear radius arms on the s3? and if so, did they do that by changing the mounting points on the chassis or the axle?

I don't know the answer to any of these questions John, they are just things that sprung to mind. The best place to ask is on Exile Rotorsport.... the guys on there have loads of technical expertise at modifying Rotaries.... RX3's, 4's etc, etc... I bet some one on there will give you the sp on the lsd's...
here's the link...

http://www.exile-rotorsport.com/index.php

.

The drive shaft flange is different for a start