Hi Everyone,

I've reached an impasse with my 1985 GSL. She was in decent condition when I got her but clearly needed some reconditioning. Engine had been rebuilt at 190xxx, and she's currently at 254xxx. My plan was to do steering parts (purchased), window seals (purchased), RB springs, dampers, brakes (disc & pads), front wheel bearings, and to replace the broken combination switch which had been bypassed, then maybe go ahead and start customizing things I didn't like (like the location & feel of the window switches, I'd rather have toggles). But I digress.

When I was shopping for an FB, I specifically limited myself to GSL and GSL-SE (later JUST GSL because I decided I preferred the way the 12A feels) because having a limited slip differential is a must for me. I didn't even go look at GS and S models in my area which I may have been able to get a better deal on, specifically because I was unwilling to deal with an open diff.

Well after I got new tires (& wheels, see previous thread), I finally had the rubber to start tackling hill climbs with glee . Down into second, throw her into the uphill hairpin, then roll onto the throttle and... the inside wheel spins & all forward acceleration stops. Serious, serious blue *****. At first I wasn't too worried. This car has a quarter million miles on it, and it has a clutch-type LSD (I have a newfound respect for viscous LSD's now). So sure, the LSD is worn out. No biggie, I'll rebuild it.

Well I've been on threads, on auto parts sites, on Mazdatrix, Racingbeat, Atkins, you name it. I called several local rotary & rear end specialty shops. Everyone tells me, I'm S.O.L.

The closest thing to a solution I can find is apparently there is a $1200 torsen diff which can be made to fit the FB. This is infuriating as rebuilding the clutch pack wouldn't be nearly that expensive, and at that rate I could have gotten a simpler FB without all the power goodies to break, and possibly found a lower mileage example. I might be willing to drop $1200 for the diff on a $3000 car IF I planned to keep it indefinitely, but I know I want to hop aboard a 09-12 RX-8 when the wife and I start a family, since (A) it will be less likely to kill me and (B) I can put a car seat in the back. My plan has always been to sell the RX-7 when I get to that point in my life, sometime in the next 3 or 4 years.

With all that in mind, I am having trouble justifying to myself dropping money on springs & shocks to get the car to handle the way I want, when I know I can never make it put power down the way I want. And if I can't justify making it handle the way I want, then what am I doing, and should I just sell her and move on to my next project? No. I'm not ready to live life without a wankel, and I'm not happy about the idea of going for an early RX-8.

SO... this is a cry for help. Does anyone out there know how to get my diff to lockup again? Where I can find the parts I need, or if there is some way to tighten it up so it works with worn clutch discs? And no, welding my diff is not an option . Not only is that dangerous but it will cause absurd tire wear with the number of corners I drive around on a daily basis. If I wanted a drift missile, I'd have started with a car with a rack & pinion steering setup.

 

You can have the clutch pack shimmed:

https://forum.miata.net/vb/showpost....2&postcount=21

https://www.rx7club.com/2nd-generati...-trick-942835/

 

85 GSL so you have the larger axle. You can use a Miata Torsen type 2 from a mid 90's car, you can also use the gear set as well so buying a complete diff is not a problem although you will need to swap it into the GSL carrier. This is what the T2 torsen will look like

https://www.rx7club.com/2nd-generati...-type-1118373/

If you have no drive it sounds like you have broken the inside lugs on the clutch plates inside the lsd and they should just need replacing as well as a bit of shim to tighten it up if you want to keep the clutch pack lsd. Viscous lsd's are generally a lot harder to shim up and get working again so better to stick with Torsens or plate type LSD's.

Your other options would be

NA S4 or S5 LSD..... not Turbo
Miata LSD's mid 90's..... can include all aftermarket types..... Kaaz, Cusco, Giken etc

I rebuild the earlier type Mazda LSD's in here in Aust as a hobby and carry parts so if you need Mazda part no.s when you have yours stripped down let me know.

 

 

Hi All,

Thanks so much for your replies! I just discovered a small pool of rainwater in the driver's side footwell so this has dropped on my priority list, but this is a lot of good information!

This looks like it's specifically for the FC diff. Is this kind of hack universal across all clutch-type LSD's? It seems odd that the rear end shops I've talked to didn't seem to think they could help. If all it takes is shims you'd think they'd at least want to look at the diff.

I didn't know the third member of the IRS diffs from the Miata and FC were compatible! I will definitely look into that. Do you know of any threads which show this being done? I'd like to be certain the splines on the halfshafts will fit into the third member properly.

A torsen diff would be lovely and worth a $500 upgrade, though I'd still be frustrated that I bought a GSL for nothing (I prefer manual windows and cloth seats). Although, I guess having rear discs instead of drums is nice.

- When you say "buying a complete diff is not a problem" do you mean I shouldn't take the ring gear off my clutch pack and install it on the new torsen third member?

- When you say "If you have no drive" what does that mean? The car drives fine until I try to accelerate around a sharp corner, and the inside wheel spins as if the diff is open. I suppose that the lugs which attach to the clutch plates could have broken, but I'd think they'd roll around in the diff and jamb things up. I guess the bottom line is if I really want to know what's going on, I've got to get in there and take a look.

Another thought occurred to me today (after I was done freaking out about having a puddle in my footwell). What happens in a clutch-type LSD if you put regular diff fluid rather than LSD fluid? I know that's a big no-no but I don't know what the prior owner did. Does putting regular diff fluid make the clutches slip/not lockup? If that's the case then maybe I should try changing my diff fluid after I inspect the diff?

 

Really depends on what you want to do with the car.

For normal street driving all of the LSD's are good options. The plate type lsd's will eventually wear out and allow slip. The torsens are a very good option as they are always consistent with their lock up and generally never wear out. I have installed some Miata T2 Torsens into a mates Group NC RX2 circuit car ( custom 26 spline axles in a floating diff ) and he loves them, basically comparable lap times with a tight plate diff but he feels the car is much more stable.

Race cars using plate lsd's generally need to have them tightened up regularly due to the higher speed cornering which creates different wheel speeds and the plates then start to very quickly wear down, different wheel speeds equals axles/lsd internals spinning at different speeds unless they are extremely tight, but then that creates understeer because the axles are not allowed to spin independently. Its a find balance to try and get the perfect balance.

The aftermarket lsd's are better, if they fit your budget, than the OEM units as they have later design and material options allowing for more wear plates per side meaning longer lasting preload inside the LSD. The Trax Tomei and Giken's are generally set very tight and can create wheel skip and understeer issues for standard road cars unless they are reset before installing.

I have a liking for Torsens due to the nature and reliability of them for road cars because you set them up and never really have to worry about them again unless they get treated badly. Race cars are generally being pulled apart every year so diffs can be reset while they are apart.

 

[QUOTE=ThirdPedalNirvana;12244496]Hi All,

Thanks so much for your replies! I just discovered a small pool of rainwater in the driver's side footwell so this has dropped on my priority list, but this is a lot of good information!



This looks like it's specifically for the FC diff. Is this kind of hack universal across all clutch-type LSD's? It seems odd that the rear end shops I've talked to didn't seem to think they could help. If all it takes is shims you'd think they'd at least want to look at the diff.



I didn't know the third member of the IRS diffs from the Miata and FC were compatible! I will definitely look into that. Do you know of any threads which show this being done? I'd like to be certain the splines on the halfshafts will fit into the third member properly.A torsen diff would be lovely and worth a $500 upgrade, though I'd still be frustrated that I bought a GSL for nothing (I prefer manual windows and cloth seats). Although, I guess having rear discs instead of drums is nice.

- When you say "buying a complete diff is not a problem" do you mean I shouldn't take the ring gear off my clutch pack and install it on the new torsen third member?When you say "If you have no drive" what does that mean? The car drives fine until I try to accelerate around a sharp corner, and the inside wheel spins as if the diff is open. I suppose that the lugs which attach to the clutch plates could have broken, but I'd think they'd roll around in the diff and jamb things up. I guess the bottom line is if I really want to know what's going on, I've got to get in there and take a look.
Another thought occurred to me today (after I was done freaking out about having a puddle in my footwell). What happens in a clutch-type LSD if you put regular diff fluid rather than LSD fluid? I know that's a big no-no but I don't know what the prior owner did. Does putting regular diff fluid make the clutches slip/not lockup? If that's the case then maybe I should try changing my diff fluid after I inspect the diff?

 

 

Have you tried to contact any Australian shops for the clutch pack? Maybe UK?

 

Alright, this thread is gold - I'll be the first to admit.

 

 

Nope, not for sale. And if I did, I'd be looking for someone who wants to drive it. Unless you are interested in buying a LSD third member that doesn't work?

I've got to get into the diff but I've got so many other things to tackle. Glad to know I'm not S.O.L. so it's worth tackling them. If I end up buying a used torsen I will probably pick up some 4:10, 4:44 or 4:77 gears. This guide for adjusting the ring & pinion tooth pattern looks useful: https://www.ringpinion.com/Content/B...h-Patterns.pdf

P.S. No clue how the car filled with water, but she's successfully dried out. Towels + Patience + hair dryer.

 

A dehumidifier is your friend when water gets in. I used to have water splash through the cabin air fresh air intake and also through a hole on the floor in car washes. Now i have a Miata that leaks in new ways. If you are interested, I've made offline copies of everything needed for an lsd rebuild. I have my 84 big bearing rear apart now if you need any measurements. The clutch discs are still out there new, just need the part numbers and persistence to ignore those who say otherwise. Would you set it up as a gsl or -se clutch pack? I can post that word doc tomorrow if you want, plus a few other resources I've been collecting...

 

I am not claiming credit for this, that would be for steve84GS TII. I merely collected the info from different sources, edited it and condensed the useful information. If you find errors, omissions or better info, I can add it to the original.

 

 

Alright, if you are interested in buying the clutch pack LSD third member that isn't locking up, I'd be willing to talk to you about selling it so I can replace it with a miata/torsen third member. Are you interested in the ring & pinion too or just the third member? Go ahead and PM me. Shipping is probably going to be ugly. Out of curiosity, why are you interested in a posi clutch pack that isn't working right?

The only thing is I can't make any promises regarding timing. I've got higher priorities at the moment than fixing my diff, but I am absolutely willing to open a dialog and sort this out. I'd probably want to agree on a price, then I'd get the Torsen and install it, and then do the transaction and ship the unit after I confirm that I won't have my car up on jack stands looking for a diff that fits. Open diff is better than no diff.

 

Thanks, I don't think I'll have my diff out while yours is. Do you know what the part numbers for the 84/85 clutch discs are? I never searched by part number, just looked for rebuild kits.

 

Open up the word document I posted, everything needed should be there: parts diagrams, bearings, clutch disc PN's, sources for some of them. Scroll to the bottom. If I missed something please let me know.

If any mods want, I can create a thread that has all of that info in a couple posts. Don't want to steal Steve's credit, I just added to it, that's all.

 

I cannot open it up. Every time I try, I get an error.

 

Try saving it locally, then opening it. Otherwise, I'll save a copy to the older .doc format. The .docx is 2013 word + (I think)

 

Double Post

 

Try either of these, the formatting on the .doc got a little messed up when I back dated it. The pdf should be good though.