JZX100 LSD Centre Install

Long time no post. I’ve got a lot to catch up on at a later date but for now here’s a guide on installing a diff centre.

I decided to use an FT86 Diff housing/gears as they’re a higher ratio (usually 4.08 though I believe 17+ is 4.3). The centre that’s going in is a used TRD 2 way that I bought. 

You’ll need the following tools/supplies:

- Dead blow hammer or rubber mallet

- Pry bars

- Chisel and punch

- Vice

- Torque wrench

- Ratchet and rattle gun (can get away with a breaker bar)

- 17 and 14mm sockets

- Razor blade

- Drill with wire wheel (recommended but not necessary)

- Sealant

- Needle nose pliers (recommended but not necessary)

- Red thread locker

- Marker or paint pen

- Brake cleaner and cloths

Drain the diff first if you haven’t already then zap off the 14mm bolts from the rear hat. Once they’re off, use your soft hammer to pop the hat off. 

Success. It’ll take a few decent taps to get it off.

Zap the 17mm bolts out of the threads for the bearing caps then wiggle the cap using the bolts to separate it. Place the caps on some marked cardboard to note the orientation.

Once they’re off, use a pry bar to start lifting the centre out.

Once you run out of range, just wedge something else under the pry bar.

And then find something thicker when you run out of range again lol.

You’ll reach a point where you can pry it out completely using two pry bars.

Place the centre down making sure you keep the shims on the correct side for reassembly later.

If your centre has locking tabs you’ll need to flatten them with a chisel or screwdriver.

Zap the 17mm bolts off and remove the locking tabs. Hand thread the bolts back in a few turns and start tapping with your hammer in an alternating pattern to start sliding the crown wheel off.

Once there’s enough of a gap, slide your pry bar in and keep prying around. Place a cloth or cardboard underneath to protect the ring gear once it pops off. 

Quickly wipe it clean then slide onto the new centre as much as you can ensuring that you align the holes.

Use the hammer to tap it on further.

Hand thread in two bolts once the ring gear is on enough. If the bolt won’t easily hand thread in, tap the ring a few more times till they will. Quickly hand tighten them to pull the ring up further.

Pop in another two and repeat.

Then pop in the rest and hand tighten till the ring gear is seated fully.

Pop the bolts back out and clean the threads with brake cleaner.

Then run a line of red thread locker along each bolt.

Pop the centre into a vice then pop all the bolts back in. The TRD centre doesn’t allow the locking tabs to be used. 

Here’s the torque specs from the factory 86/brz manual. 

The ring gear bolts take 97nm/71ftlb.

Tighten in a star pattern. Helps if your bench/vice is floor mounted too lol. You can get away with hitting the bolts for a few ugga duggas but always torque them if possible.

Double check that all bolts are torqued and mark them as you go.

Remove the old sealant with a razor blade. I recommend placing a cloth inside the diff housing to catch bits that fall off.

You can also carefully use a wire wheel on a drill at low speed to fully clean the surfaces as the razor blade may not remove it all due to the grooves.

Place the shims on the correct sides and pop the centre in. You might need to give the centre a few taps to get it in and you can use a flat punch to carefully tap in the shims level to the bearings. Also check that the ring gear is engaging on the pinion correctly.

Refit the bearing caps ensuring they’re in the correct order then snug them down with a ratchet. Also check for any excessive backlash by wiggling the centre to check how much play there is. If you have a dial gauge then now is the time to use it (I don't unfortunately but backlash was okay).

You'll usually get away with refitting the shims in the correct order unless you're changing ring/pinion or there's excessive wear.

The bearing caps take 85nm/63ftlb.

Pop it back in the vice and torque them down and check over once more. Mark to signal that they’ve been torqued. Once torqued, check that it all spins freely.

Give the mating surfaces a few wipes with brake cleaner.

Was taught by Phuong to use needle nose pliers to roll the tube of sealant. Makes it a lot easier to control and keeps it looking neat.

Run a bead along. Be careful to not use too much as it'll get squashed.

Pop the rear hat on and finger tighten the bolts till sealant starts oozing out. Let it sit for an hour then come back (this part is dependant on the sealant but most advise to do this).

Set your torque wrench to 47nm/35ftlb.

Snug it up by hand with a ratchet in a star pattern till you've felt it seat then go over with the torque wrench.

And that's it. Let the sealant cure for 24 hours before filling with oil. I also recommend writing a note in case you forget.