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Discussion Starter · #1 ·
This Is a basic tutorial to show what the basic steps are for swapping an LSD from an 86-89 supra into your IS's stock rear diff.

:note:

If you wish to retain your stock gearing, (3.73:1 or 3.91:1), you can, but if your not planning on boost, the 4.30:1 or 4.10:1 gearing may give you a free boost in performance at the sacrifice of top speed. In my case, I estimate that my top speed dropped about 10-15 mph. Thats 10-15 mph hour that my IS has seen maybe 3 times in nearly a year. I'll gladly trade that for lower 60' times or more power where i use it.


Ok. to start with, I'm assuming you know where the diff is, you have already bought your diff from the supra and are ready to remove your diff. I'm also going to assume you know how to use basic hand tools and a sledgehammer, and have the organizational capacity to keep shims separate and on the proper sides. you will be re-using the stock shims from the IS. keep the drivers side shim on the drivers side and the passenger side shim on the passenger side. so make sure you mark them.


What you need:

Stock IS differential.
Stock 86-89 supra LSD
either a cutoff wheel or another appropriate cutting tool that can cut accurately through the end of an axle.
a standard set of metric sockets with a 3 inch and 6 inch extension.
a 5-10 pound sledgehammer and the balls to use it on a potentially fragile part.
a pry bar
a claw hammer
an impact wrench.


What you do:

with both differential's out of both cars and drained, remove the axles.

using liberal force with a big hammer, beat out the axles i assume you'll know what direction to hit it. you'll have to hit it alot of times, really hard. it will eventually brake loose.

with the axles removed, remove the cover plates.

Open:


Clutch type LSD:


you can clearly see a difference. in the gears, but the internal part of the case is exactly the same.

remove the two bolts on either side which hold the ring gear in place, and simply pull out the ring with spider gears from the IS diff and the ring with the LSD from the supra diff. comparing the two, you should notice more gear teeth on the supra diff, and you should obviously see the lsd.


now, if you don't want to change gearing, simply remove the Ring gear from the lsd, and bolt on the ring gear from your IS. 130 foot lbs should be right about perfect. slide the assembly back into the case reusing stock shims. then read ahead for the last part.

if you wish to change your gearing:

remove the drive shaft mount from both diffs. you should have removed a 30mm locking nut. screw the supra nut back onto the supra diff. make sure 2 or 3 threads are still out on the nut. you DO NOT want an exposed end of the pinion shaft. now put the diff pinion side up, with the open end on the table or floor. take your trusty sledge and give it a good wack or two. the pinion should drop without damaging the pinion seal. remove the nut from the pinion, and slide the pinion out of the back of the diff. using the same supra lock nut, repeat on the is diff using extreme care! this is the diff that absolutely cannot leak. once that pinion is removed, put the supra pinion into the IS case, and use your impact to essentially press in the pinion properly, but be careful not to over torque. i used a 2X4 to keep the pinion from spinning while i used the impact. once the pinion is properly seated in the diff and has no side to side play or fore aft play, slide in the supra ring and lsd.

now for the cutting part. on the stock IS axles, you will see a notch at the end of the splined part. you need to cut off that 1/8th inch stub.


before cutting:


after cutting:



if you skip this step, you wont be able to slide the axles all the way in.


once thats done, slide in your axles, re-attach the pieces that hold in the ring gear, and test to ensure every thing spins freely.

now re-attach the cover plate, using black rtv sealant to form a gasket. apply liberally. next fill with 1.5 quarts of your choice of synthetic gear oils ensuring that they contain the standard lsd additive. mount it in the car and enjoy!!!


sorry if this isn't detailed enough, but i lost some of my pics. at least the crutial ones are there.
 

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Yea, you're gonna have to help me do mine when I get it, because while I do have the hammer I don't have the balls to smack my diff. with it....

Good tutorial BTW
 

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Glad to see you get his up Avernier. I was kinda regretting not doing a write up on this when I did my Mk3 diff in my car. Guys everything he has posted is 100% accurate. I have been running this setup for 40k miles at this point, and they have been hard track miles too. +rep to ya man.

-Joe
 

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Discussion Starter · #5 ·
thanks for the kind words guys.
 

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Hm this is interesting, I might have to look around some junk yards, but with boost coming up is the 4.30:1 or 4.10:1 (which ever is for auto) still worth it or should I keep the stock IS gearing (auto)

Edit: I searched for it and see 4.30 ratio locking w/o turbo is that ok?
 

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Discussion Starter · #7 ·
theres no correlation between trans and gear ratio. and if your going boost, just keep your stock gearing, you'll want it.
 
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Discussion Starter · #9 ·
i bought my lsd from a you pick it place. 46$ and it was mine.
 

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You forgot to add the 6mm or 8mm hex sockets to remove the axles, as well as the 12mm hex socket to unbolt the rear diff mount, or you can just unbolt the rear half and leave it in the car. And re-use all of the is300 shims, both of our cars are that way and no need to re shim it at all.

Also the turbo 5spd 90-92 models come with a 3.73 final drive if you want. Avernier's was an 89 n/a auto rear end, I believe.
 

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Discussion Starter · #13 ·
You forgot to add the 6mm or 8mm hex sockets to remove the axles, as well as the 12mm hex socket to unbolt the rear diff mount, or you can just unbolt the rear half and leave it in the car. And re-use all of the is300 shims, both of our cars are that way and no need to re shim it at all.

Also the turbo 5spd 90-92 models come with a 3.73 final drive if you want. Avernier's was an 89 n/a auto rear end, I believe.
mine was an 86, and i don't know for sure if the 90-92 ring wil fit our case. i'm not possitive they're all the same.


and i didn't mention how to get the diff out because i figured anybody could figure that out.
 

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That ring that we had from my mk3 diff was an 90-92 3.73 final drive and was the same size. Remember, that is why we swapped your ring and pinion as well.
 

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quick question:

Would this work on a rear diff of an IS300 that does not have LSD? Or would I have to pick up both an IS300 LSD and a 86-89 Supra LSD?
 

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That is half of the point of this swap, adding lsd. You do not have to swap final drive ratios if you do not want to. I just used the LSD out of my mk3 diff, while Austin used the ring and pinion as well as the lsd for his swap. both of our cars had open diffs to begin with.
 

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Another question just to make sure, to get the supras better performing final drive, that is the swapping of the pinion and rings
So do everything listed above to go from IS 3.73/3.91 to supra 4.30/4.10?
Just wanna make sure before I get a diff and do all the work and not mess up. I am planning on boost but that is long down the road. I'd keep the supra final drive in the car until I have a turbo ready to go in, then do work to the diff to put the IS final drive back in. Is that a good idea?
 

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using liberal force with a big hammer, beat out the axles i assume you'll know what direction to hit it. you'll have to hit it alot of times, really hard. it will eventually brake loose.
Just another trick for this part. You can use the axle bolts to pull the axle out by threading them down onto a scrap shim.

And for those that decide to keep the stock ratio and swap rings onto the LSD, you'll need quite a bit more tools - particularly a press. More info here: http://my.is/forums/f114/re-gearing-differential-399291/

And you really should use measuring tools to make sure the pre-load is set properly and that the ring and pinion mesh properly. Refer to the Toyota repair manual.
 

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Discussion Starter · #20 ·
can you say full counter steer donuts? i can. and its wicked easy. plus pulling in 4th instead of down shifting into third is way cool.
 
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