How To Shim a LSD

[Saki Steve]

Well The plan for tonight is to pull the Rear Diff Out of the rx7. Now, I have never rebuilt a diff, or even shimmed one for that matter. I have been reading up on it and it seems like it is pretty easy to do as long as you mark and measure everything correctly. Now I have read many different ways to do this. Some add more clutch packs, and others just shim the thrust washers. Well. I believe that what I’m going to do is shim the thrush washers, and replace some of the bad clutch packs with new friction disks. After Reading, it looks like about 2 shims, will make the diff behave similar to a Kaaz 2 way depending on how thick the shims are and how good the clutch packs are. I am guessing this will cost me about $30 if I just need shims and $90 if I need all new clutch packs. The Nissan R200 are supposed to be quite simple also and cheap, around $35 in Parts. But I think this will be good for a write up. I will Post pics as I work through the process.

[Silvia Surfer]

u have an r200 rear end? cool.

[Saki Steve]

So I finished rebuilding my rearend, I was going to shim it, but, shims are really hard to make. well with the tools that i have. But on the otherside, I did buy all oversized fiction plates and Conical springs, So.... My diff is almost totaly lock, it is pretty agressive, I can hear it squak the out side tire every so offen, but only after, i had made sure it was locking. And it spin MUCHO better, but i only have gotten to drive in the rain.

[Dori Ninja]

i will be modding my diff shortly after i get the fucking thing running again!!! lol but i will be doin this......http://forum.teamfc3s.org/showthread.php?t=52983

[Saki Steve]

It is basically what i did.

[Saki Steve]

I'm doing anther Rear End On A Rx7 for Brian Peters Friend.

[Saki Steve]

A quick guide to what you need to do (now with pictures!). If you're not confortable with pulling apart a diff or don't have the tools needed then find somebody who can, i.e. a diff specialist.

In saying that, I'll do the whole job drive in drive out for $400, or $220 if you bring the diff to me. You think my prices are too much? do it yourself .


Step 1:
Jack the rear of the ol' beasty up nice and high so you have plenty of room to move around. Make sure you put some Metallica on to get you in the right mood for it - none of this Reload crap, some Master of Puppets or Ride the Lightning!

Step 2:
Drain Diff oil. There is a plug on the bottom of the diff housing that you can use to drain it into a suitable container. Make sure you do the drain plug back up tight so you don't forget about it later. It's a good idea to wipe the metallic sludge off the magnet with a rag (you'll see what I mean). Also, if you want to re-use the oil, drain it into a clean container. It is a good idea to change it though. I'm not sure on how much oil it takes exactly but you just have to refill it until it starts comming back out of the checker plug, located about halfway up the diff housing.

Step 3:
Make sure handbrake is on firmly. Loosen the 4 bolts holding the driveshaft to the diff flange. If you can't reach them all put the gearbox in neutral, remove the handbrake and rotate driveshaft to suit then repeat.

Step 4:
Once you have loosened the 4 driveshaft bolts, its time to tackle the half shaft flanges. on either side of the diff there will be a stub with either a 5-bolt pattern (gts-t, factory turbo a31/c33) or a 6-bolt pattern (3 lots of 2, regular a31/c33 etc etc). Once again if you can't reach them all remove handbrake and rotate wheel etc. Some CRC won't go astray either if this is the first time the diff's ever been disturbed. The reason you do this last and the driveshaft first is that if you unbolted the 2 halfshafts first you couldn't utilise the handbrake to hold the driveshaft still while you undo the bolts.


Step 5:Now we're ready to remove everything. Before you do this make sure all the little bolts are removed that you're cracked off. the driveshaft will 'lever' out of the way with a screwdriver but the driveshafts will be a bit tricky. the 6-bolt driveshafts have 'lumpy' things in them that sit in a 'cup' on the halfshaft stub and are difficult to lever out of the way. 5 stud flanges are just 2 flat faces and are easy to slide out the way. There are 4 nuts above where the hicas rack is (if you have hicas) and 2 bolts towards the front by the driveshaft flange. remove these all and the diff will fall on the swaybar and sit there. Then it just takes a bit of dicking around to get it out. It will be quite difficult if you have a gts4/aftermarket swaybar installed. If you cant get all the doohickeys out at once, try removing a half shaft. Apply handbrake and remove the 36mm nut in the center of the hub. then u can remove halfshaft to give u more room.

Now, with a bit of luck (and maybe a trolley jack too) you have the diff infront of you. It's quite a heavy f**ker yea?


Step 6:
remove the rear diff cover (the alloy piece). Before you do anything else tap the axle stubs out of the diff housing (the bits with the flange on them). tap them hard from behind and they'll come out (you know you love to tap it hard from behind). Make sure u mark them left and right. Now under the diff cover there are 2 bolts either side, undo these and remove the bearing caps (again remember which way around and what side these go on). You will then see some bearings and spacers and things beside the diff head on either side. Lever the crownwheel out with a big bar and make sure u keep all the bearings etc in the correct order and sides (a vivid is handy for marking everything with terms like "inside, outside, left, right etc).

Step 7:
Now you have an oily diff head funky lookin' thing sittin there. There are several (about 10?) large bolts holding the crown wheel on. They are FUCKING tight!!!!! I'd recommend a decent vice and large powerbar or something - alternatively a pneumatic gun will work. Once the crownwheel's off, you'l see 2 large phillips screws. Remove these and off comes the viscous center. You'll see once u pull it off a washer sitting on a flat surface. That's your original preload shim - See below for a rough indication of what it looks like in new form.

Now the original plan was to double that thickness and put more load on the viscous center, somewhat 'reviving' it to how a LSD should be. If you're me however (you wish!), 1 extra shim just isn't enough for drifting (it is great for everyday driving however). So go on, be a devil and chuck 2 extra ones in there if its mainly for the dr- ifting.



This is what I posted about them on another thread, be your own judge about how many extra to put in:




Add 1 new one to the existing one (total of 2) if you want a decent predictable lsd for driving that spins up 2 wheels with ease. Comparable say to a BRAND NEW viscous diff (i.e. not worn out, you've probably never driven on one).


Add 2 extra preload shims to the existing one (total of 3) if you want a very solid diff that's very tight but not quite locked (comparable to say a kaaz 1.5 way mechanical).


Add 4 extra preload shims to the existing one (total of 5) if you're a crazy c*** and see if it actually works.




Step 8:
Do everything in reverse, make sure you listen to Metallica again!

**VERY IMPORTANT NOTE:**
before you screw the diff center back together after inserting shim, take the 'longer' of the 2 stub axles and insert it through the center of the diff all the way. This splines the 2 different splined parts of the diff center together so that when you go to insert the diff stubs at the end they'll actually fit (easiest way to explain it). Otherwise you'll be screamin' your head off wondering what you did wrong.

Pour the diff oil in before you put the backing plate on. Hopefully the gasket for it is in alright condition, just use some high temp sillicon to seal it before u bolt it up so it doesnt leak everywhere.


Just a little more info on the shim - It costs aroundabout $17ish including freight from japan. Usually about a 10 working day wait, usually less. You'll need to order this from your local Nissan Authorised Dealer. You could also rob one from another lsd but not worth the hassle of pulling 1 apart. The part number for them is as below:






Hope this helps, if it looks a wee bit daunting for you (it ain't that easy) and you're in Auckland I can do the job for you, as little or as much of it as you like (as above). If you think I've left anything out or have any questions just post a reply so everybody can see it.

[Dori Ninja]

hey saki, where do u get the parts for the rebuild?? i was watchin some footage of my last drift event and it looks like my diff isnt locking both tires all the time....idk, the file is all shity on my comp so i gotta dig out the tapes again, but since i am gettin the motor i figure y not do up the dif too? lol

[Saki Steve]

The three ways to get the parts,
1.) You buy brand new parts from Mazda (What I did, and I oversized everything, the “right way to do it”)

2.) Get a old used Diff, and take it apart (nice because the worn pressure discs can act as good shims and come in sizes that are smaller because they are worn, that’s good depending on your tolerances ”still a good way of doing it”)

3.) You can make shims, out of old cans and old brake clean bottles (these are good cause they are cheap “I wouldn’t use unless I needed it for fine tuning”)

[Dori Ninja]

so do u have to hit up the stealership or do places such as auto zone or napa carry these??

[Saki Steve]

Stealership! Cost me like $250ish, but if you got extra rear ends can be really cheap

[Dori Ninja]

yeah itll be abot the same from mazdatrix....we'll see what i do when this motor is paid for!

[Saki Steve]

This works Great!