How To Install A Aftermarket LSD (not for faint hearted)

Welcome to Chrispy's guide to mucking about with the rear end of your Zed part 2 of 3 I was very hesitant to install the LSD myself and couldn't find any good writeups on the net. The instructions that came with mine where entirely in Japanese But I gave it a go and it all worked quite well This is up the slightly more tricky end for the DIY-er and requires tools that aren't found in the typical shed. If you want to shim your standard diff then you will have to do most of this, so pay attention. I may strip down my old diff centre for a how to on that too. I've got a Nismo 1.5Way clutch pack LSD to suit the R200 diff. It came with the diff centre, new driveshaft bearings, oil seals and cover gasket. I would recommend replacing all of these while you have it apart. If you diff didn't come with them go and buy them from Nissan. If you have a different diff it should all be largely the same. This particular diff has been discontinued and are getting hard to find. They have been replaced by Nismo's new GT range which is very nifty (but very pricey) as you can adjust the breakaway torque while it's in the car and if you so desire pull it to bits and covert it to 2 way or 1.5 way.

List of tools and stuff: Usual 1/2" socket set with 14mm, 17mm, 19mm sockets 1/2" breaker bar Cheater pipe if you are skinny like me Torque wrench that will go up to 140 ft/lb Dial gauge with magnetic base Engineers Blue Slide hammer Normal hammer Assorted punches Screwdrivers for levering Small crow bar/pinch bar Shop press or blowtorch Rubber mallet Big bench vice, I used a 6" offset. Rags Loctite New diff oil, make sure it's to suit the type of LSD you have. Normally a LimSlip type, around 75/90, see what it says in the manual or what others have said on the net (ask drifters, they love diffs) The workshop manual available in the tech section, exploded views can help. First up remove your diff from the subframe. No piccies or anything. If you need piccies you probably shouldn't be doing this Remember to undo your ABS sensors and don't drop it on your fingers as it's heavy.

Drain all the oil, you should probably have done this when it was still in the car as it's quite awkward otherwise. Remove the rear cover. Just undo the 8 bolts and pop it off with a screwdriver. This is what you will see.

Mark the bearing caps to show left and right, and orientation. They are line bored so need to be put back in the same spot.

Now is the time to measure ring gear to pinion backlash, it should be between 0.05mm and 0.15mm. Mine was about 0.14mm. Write it down if you can't remember. Just gives a figure to compare at the end. Also measure the runout of the ring gear, it should be under 0.05mm. Mine was 0.04mm. There are some nice piccies in the workshop manual if you want to know where to stick the dial gauge. Grab the input flange of the diff and give it a spin by hand, it should take around 1-1.3N.m to turn it. I don't have a gauge to measure this, so I just tried to 'remember how it was'. This isn't quite so critical IMO. I'll explain more later. Remove the driveshafts using a slide hammer. I don't have a slide hammer so I used a bit of threaded rod, few nuts and washers and a bit of plate I had and made one. Sorry no pics of this.

Remove the bearing caps and put somewhere safe.

Here you can see the preload and locating shims next to the bearing.

Remove the centre of the diff. This can be a bit tricky. I GENTLY levered with a crow bar against the old centre and the housing. There is a fancy special tool that Nissan sell, but that's probably not worth it I've heard of people using the slide hammer to get them out. Put the bearing shims in little bags labeled 'Left' and 'Right' THIS IS SUPER DOOPER IMPORTANT! DON'T DO THIS AND PREPARE TO CRY LATER ON. Tada!

Undo all these bolts that hold the ring gear on. These are on REALLY FRIGGEN TIGHT. My rattle gun wouldn't budge them and that apperently does 400N.m of torque The bolts are stuck in with thread locker.

This is what I used to undo them.

Once that is done gently tap with a rubber mallet equally around the edges of the ring gear and it should slip off. Noice!

Put the ring gear on your new diff centre. Gently tap it down and put in 4 bolts to hold it in position. Do them up cross pattern like a wheel and a bit at a time so you don't bind one side. Then put the rest of the bolts in, drown them in thread locker, you don't want them coming out! Torque them up to 70ft.lb or so in a cross pattern, then torque them all the way up to 140ft.lb (190N.m). It doesn't say to do it staggered like this in the manual, but I thought it best. I marked the heads of the bolts to know where I was up to. 1 mark for loctite, 2 marks for first torque setting, 3 marks for full torque setting. That way you won't forget

Clean the mating surfaces for the new bearings with a clean rag. Then press them on using a press, or you could probably heat them with a blowtorch and just slip them on. We used to use inductance heaters at work, same principal just a bit less even. I used one of the driveshafts with the press as it fit the bearing perfectly and gave a even spread. The bearings are taper roller bearings, so they come in 2 pieces. I used the outer piece in conjunction with the inner while pressing them on, seemed the best way to do it. MAKE SURE YOU PUT THE BEARING ON THE RIGHT WAY! Small tapered end goes OUT. If you do it the other way it will be a PITA to get off. There is no left and right by the way.

This is what it should look like now. Press the bearing down until the bottom face of the bearing is in full contact with the machines edge on the diff centre.

Do the other bearing as above.

Now is a good a time as ever to remove the side oil seals. Mine where well and truly stuck in and required a love tap with a screwdriver and a hammer. Don't put the new seals in just yet. Please not there is no lip for the seal to bottom out on, so take care when installing the new ones.

Clean the bearing seats within the diff casing. Use a clean rag. If you leave them dirty you may have trouble with runout and alignment of the ring gear and this will cause crying. What it should look like:

What it looked like on the otherside untouched:

Also clean the bearing caps, but don't wipe off your locating marks on top

Next mount the diff casing in your big vice like so.

Now this is a little bid fiddly and awkward. You have to put the diff centre back into the casing while holding the outer bearing races in postion. The diff centre is pretty heavy and covered in pointy bits so take care. Once it is in position put the old bearing shims back in after giving them a clean. Just tap them down gently with a hammer. Again Nissan make a special tool, I found if you where careful with a hammer, and then a punch it was fine.

Just a note on these shims. The shims have 2 purposes. One is to locate the diff centre relative to the pinion to ensure proper meshing of the teeth (we will check that later). The other reason is to keep a preload on the bearings as they are taper roller bearings you don't want them flopping around within the housing as you get on and off the throttle as you have pretty big axial loads with hypoid gears. The service manual has this fantastic method for determining the size of the shims to ensure proper preload. It involves finding the stamped marks on the diff casing, ring gear, pinion and diff centre. So as we have replaced the diff centre we can't work it out (and I couldn't find the pinion marks, rest where there) There was no marks on my diff centre even though it was a Nismo and you would think they would have thought of that Put the main bearing caps back on and torque the bolts up to 70ft/lb. Chuck a good gob of oil into the bearings via the driveshaft hole. This is why we didn't put the oil seals in before. Give it a spin via the input flange. It will probably feel tighter than before. I found it was really tight at first, but once I got some oil on the gears and in the bearings it loosened up nicely. Still a touch tighter than before, but passable IMO. Brand new bearings, so they should wear in a touch anyway. Tap the new oil seals in with a bit of new diff oil around the outside. Please note that the new seals have grease to help them seal, so don't wipe this off This is the moment of truth! Measure the runout and backlash again, should be within the tolerances I noted above and you'd expect them to be VERY close to what you measured initially. If that is fine you can breathe a small sigh of relief.

Next is to get some of this stuff.

It's called Engineers Blue, or Mechanics Blue. It's Prussian Blue dye mixed with oil/grease. I got this from Repco, cost about $7 and is enough to do about 350 diffs. Gotta love the instructions on the back though "Use as required" It smells really nice too, reminds me of making model planes

Give 5-7 teeth on the ring gear a good clean with a rag. Then paint some of your lovely blue die on these teeth.

Then rotate the input flange by hand a full revolution. This will make the dye rub off where there is contact between the pinion and ring gear. You can see below how mine is pretty central to the teeth on the ring gear.

If it looks like that you can breathe your second sigh of relief If it's all towards the inside, outside, top or bottom, then you should cry. Major pain in the arse. In the service manual it goes through the proper way of fixing it, mainly involves mucking about with shims to move the pinion and ring gear in relation to each other to correct the meshing. Trial and error while maintaining the same overall width of shims to keep the bearing preload correct. If you just leave it wrong then your diff will be noisy or have short life span or both If it comes out like that then I would seriously consider taking it to a diff shop and have them do it. Put the driveshafts back in (depending on the LSD centre you might not reuse your old ones). I just pushed them in by hand, the retaining clip went in easy enough. Make sure your fingers are out of the way as when they go in they go in quick!

Last of all install the rear cover with the new gasket. Torque the bolts up to 35ft/lb or so. I went a fancy chinese GReddy copy high capacity diff cover. It was for a S14, but fits the diff and subframe perfectly.

Done And for interests sake, a piccy of the old diff centre (left) and the new Nismo one (right).

For the Nismo diff you discard the long drive shaft and use two of the short ones.

And this is why, the viscous unit uses a double spline for some reason...

...while the Nismo uses only a single.