T2 differential swapped into FD

[dudemaaan]

Ealier this year (feb 18th 09) I destroyed my stock differential. I punched the gas in 3rd gear on the highway and a small uneven section of the road caused the tires to hop a little, I heard a strange noise from the rear end. It drove fine in a straight line, but any corners resulted in a terrible binding noise. I got it home, drove it over the pit, drained the fluid and had 2 chunks of metal on the magnet. I then decided to swap in a series 4 turbo 2 differential. Purchased one from a forum member for $250.

Pulling the differential took about 2 and a half hrs. It's pretty easy. Heres a couple pics of everything that needs disconnected for the axles to come out.
All images are thumbnails and can be enlarged.
Before:


After:


The drive shaft, has to be dropped, the ppf should be dropped, I left mine in place because my downpipe and midpipe are one piece and I didn't want to mess with that again. There are 4 large nuts holding the differential to the ppf and then 2 bolts that go through the differential bushings. Now is a good time to replace those if they are worn or you want to go with solid mounts. I made my own solid mounts awhile back that can be found in this Thread.

My solid mounts


Once the differential case is out of the car I pulled the cover off and removed the differential. Here's a pic of the case and the stock LSD. The small spider gears were all ground off on mine.

Case:

93' stock LSD:


When the T2 differential came in I decided to take it apart and check the clutches for wear and clean everything up. Here's a pic of the T2 LSD on some blocks to measure it, the next pic is of the cover plate removed (where the ring gear mounts), and the final pics is the LSD tore down for cleaning and inspection.

T2 LSD:

Cover plate removed:

Tore down:




The FSM for the 87 T2 differential says the specs for the clutches and disks are: New - 2mm and min spec according to the FSM is 1.9mm. THIS IS WRONG. The correct spec for new disks is 1.75 mm and min spec would probably be 1.65mm. New disks and oversized disks can be found through Mazda Motorsports or Mazdatrix I didn't need any extra parts because The T2 differential I got was practically brand new with very little to no wear.

You can also shim the differential out to have a harder lockup. People use all different kinds of things for this with coke and beer cans being popular. The mx5 forums have very good information on doing this. It can help restore a worn differential, or provide a new differential with a harder lockup. since mine was practically new I chose not to do this.

Next I mounted the ring gear from the FD differential to the T2 differential. I don't have any pics but its straight forward. Use some loctite on the bolts.

New carrier bearings should be installed, and then put the T2 lsd in the FD case. Rarely are 2 differentials the same exact size, so you'll need to use different shims to set the backlash. I got very lucky here, and my old shims worked by swapping left to right. I doubt it will work out that nicely for me again, and very unlikely for others. The shims are rather expensive through mazda and it will usually take some trial and error to get it right. Might be best to have a differential shop do this part.

Until discovering my shims would work, I considered using several thin shims from a different kind of differential.The correct size would have to be found. This would make setting the backlash cheaper and easier. If anyone ever finds anything that would work let me know for future reference. Something like This Is what you would look for. (without gasket) The shims have to be the right diameter though.

Pic of what I considered using:


That's pretty much it. Pinion is left alone, backlash is set. And also be sure if your spider gears were destroyed like mine to clean, clean, and clean. Those little gears get into everything. Hide around the pinion and all throughout the case. So get that stuff out of there before the new differential is in place. Put everything back in and fill with some good synthetic oil with friction modifiers for clutch style differentials. I used royal purple 75/140 if I remember correctly.

[TitaniumTT]

Nice write up! I did the complete opposite though, I took an FD Torsen and put it in place of my S4 TII rear Us FC guys are lucky for not having shims though, there is adjustment on the outer race which is nice.

I had an S4 N/A LSD that I shimmed and I HATED it. The lockup was WAY too much for anything but really drag. The shims speced out damn neart new as well, I should've left it alone like you did.

[dudemaaan]

Haha nice, do you autoX your car? The stock FD lsd is good for lots of turning, just not so good for launches and very high amounts of power.

[TitaniumTT]

I do auto-x my car and HOPED to get about 1/2 dozen track days this year but my mistress had other plans. I'm a little concerned about the launching though and breaking the thing. It's not even mine, it belongs to a good friend of mine while mine waits to be fixed (Vibration, cause unknown as of yet.) At what RWHP do these start to have issues? I've heard ~450 - 500

[dudemaaan]

Yeah probably around that power level. But really just depends on how much launching is done. Wheel hop of any sort kills them, even much lower HP cars can break them with wheel hop. In my case I knew I would want more and more power, and since I already broke one, I would be destined to break it again and again. I don't like replacing the same thing over and over so I got the stronger T2 differential.

Where is the vibration that you're having? In the rear end? Was it after the swap?

[TitaniumTT]

Thanks for the heads up. My FC doesn't hop, just lights them up pretty well. She's an auto-x, track day, street car so I REALLY want to keep the Torsen rear end. We'll see how long she lasts. I'm with you, I really don't want to replace a part more than once.

Yes and sort of. I say sort of becuase I never drove with that rear end prior to the swap. I bought the whole thing used from a guy who used to race e-prod and was moving to the M3's. I got everything and promptly cracked it open for the Torsen. We moved tires around and it did nothing, swapped the driveshaft, it did nothing, it wasn't until we put my buddies Torsen in that the vibe went away. Interestingly enough the flange lines up with the bolt patern, but the ID of the flange is EVER SO slightly off. You have to beat and pry the DS off the vibrating one, but not the good one. So I need to locate a pinion flange I guess and see what that does. I didn't on this one, and I should have, press the pinion flange out and check all the tolerances. I figured if it came off a race car, it shouldn't be a problem. Not high on my priorities list right now based on where his PJ is.... hell, I even has his fuel tank in my car

[Garfinkles Motor Works]

Good info as usual .I have not broken my rear as of yet but I need to copy this to keep in my file .

[dudemaaan]

Thanks.

[proz07]

once again good to hear the diff worked out for ya.... that being said i hope i dont regret it later when i drop my kaaz in mine for noise purposes. lol clunk clunk clunk

z

[dudemaaan]

Yes and thank you for having one available in such good condition and shipping it out so quick. Worked out very well.

Even if your kaaz does make some noise it's not a terrible thing for a high performance car to be on the noisy side. Are you waiting for the stock one to let go before dropping the Kaaz in??

[proz07]

yes and no..... see i have most of a rolling spare chassis that i can take parts and swap to at my liesure makes down time on my car minimal so destroying a lsd isnt to big a deal for me but ill be doing it once i get back from this deployment as right now it has alot of slop in the backlash you can feel pretty good right now.

z

[Max777]

Hmm, would shimming the TII diff work well for drifting? Right now, my diff seems like it's doing it's job fairly well, but I want to try driving with more lock up to see how it feels, maybe I will go with a OS Giken 2 way some time in the future.

http://enjukuracing.com/giken-super-...91-p-7967.html

[dudemaaan]

Yes shimming the differential would work well in drifting applications. But if you also drive on the street and you make it too tight it might not be fun to drive around

[Max777]

I'm more worried about the fact that my S4 TII diff is stock and has 148,000 miles on it... I dont think I can afford to buy rebuild clutches right now, so if I can shim it to restore the lock up at least a little, it would be a huge benefit for me.

I'm not even sure, I think if I can get a set of rebuild clutches for a decent price, then I might not even bother going with the OS Giken. Any LSD is better than no LSD, and if the TII diff can handle over 500hp, then I think I'm set.

[dudemaaan]

Well if it's out of the car its easy to pull apart and check the disk specs. I'm not sure how the disks typically hold up, but i purchased a used differential from an 87 of unknown condition and it was like new inside. Also it's only the s4 t2 that have the clutch style lsd. Other then that, yes shimming it will bring new life into it if it's worn. You don't even need much to add more lockup. I'm sure rebuilding the t2 is cheaper then buying a new os giken if it came to that.