If you're after lower gears for that bigger rubber you've undoubtedly looked at different t-case gears.. but then saw the price tag

Shocked

not being able to justify the entry level £300 odd.... 

....you then find a rocklobster conversion! same entry level 4.1:1 gears, at a fraction of the price... but then you have trouble finding the now scarce 410 t-cases needed for the conversion...

...then you hear about Vitara differential ring and pinions... whats the big difference? 

In a Samurai you have a diff ratio of 3.727:1, in a SJ413 you have a slightly lower ratio of 3.909:1

In a 410 its 4.11:1 but the diffs are of a smaller size and cannot be swapped over

In a standard manual vitara its 5.13:1!! thats some reduction!

Just to get the most important point out the way - you need TWO FRONT VITARA DIFFS a rear Vitara diff has a much larger ring gear and will not fit in a Samurai/413 casing.

First question, is it a straight swap? No... well... thats only half true at least. There are subtle differences which mean its not exactly a full on straight swap, and a few things need to be done first.

On the left is the R&P out of a SJ413, the right a Vitara 

The ring gear of a Vitara (right) is much thicker than that of a Samurai/413... 

And the pinion a LOT smaller.

And a very important subtle difference - the Vitara ring gear has a much smaller step in the inside edge.

Also, once you have your two front diffs, you will notice the casings are made out of aluminium.

Front axle

For the front of your samurai you CAN just slide the whole vitara diff into the samurai axle and use that... the side gears use the same splines as the Samurai front shafts so theres no problems there. 

This method will work just fine! Unless you have a front locker, then you might find this happening, the diff is a lot weaker due to the aluminium casing. Not to mention the Vitara only has a 2-pin front diff as opposed to the 4-pin of a Samurai

The ali casing isnt strong enough for a locker.. plus it has no oil ways reaching the rear pinion bearing which doesn't help matters.

If you want to make sure nothing like that happens then the gears will fit in a standard samurai steel diff casing, this is what needs to be done for the rear axle which is all explained below.

Rear axle

The rear axle is slightly more complicated to convert.

The whole Vitara front diff cannot be put straight in as with the front axle of a Samurai.

The main reason is because the side gears are different and will not fit the rear shafts.

On the same lines, the samurai side gears cannot be swapped into it because, as already mentioned, there is no oil way to the rear bearing. And since Samurais are rear wheel drive, this will overheat and cause problems down the line.

You're going to have to bite the bullet and build up the R&P's into a SJ steel diff casing

Wink

This is the same method if doing it to a front diff, but obviously, you will need the carrier out of a front SJ diff for the side gear differences.

So you've got your front diff ready for the off.

Before Dissasembly measure the backlash and make a note of it.

Remove the pinion bolt, and the carrier mounts so you can get the bits that you need for the swap. Don't forget the pinion flange will be needed too!

Have your Samurai steel casing ready.

Along with the 4pin carrier out of the SJ.

I've used a non-crushable crush collar for the conversion to make things a little easier.

I would not advise using your old crush collar, this should be replaced with a new one so that the correct pinion bearing preload can be set; these are available from suzuki.

The pinion is now ready to go into the steel casing. Put the Vitara flange on the end, nip it up to make it stay in place.

Remove the ring gear from the Vitara 2-pin carrier. these are tight. And I mean TIGHT! Impact wrench at the ready!

Wink

Once off, it needs to go on the Samurai 4-pin carrier.

This is where you will notice the difference of the ring gears, shown in the 4th photo down on this thread.

The smaller step in the vitara ring gear means the pins are not held in place and are liable to slide out, this is what the "can" is used for in those kits sold in the US., just a thin piece of steel that sits over the carrier assembly stopping the pins from moving, my solution: tack weld the pins on the carrier. Enough to stop them moving, little enough to grind and hit off if need be.

Grind the blobs of weld down so the ring gear will fit over them.

This illustrates what i mean when i say the step isnt big enough to hold the pins in place.

Stand back and marvel at your 4-pin 5.13:1 ring gear assembly.

Wink

Offer it up to the pinion in the steel casing. it will go quite far to the side due to the small dimensions of the pinion.

You can see just how far to the left the carrier sits (look at the bearing races) due to the small pinion. this is where the "spacer" in the US kits is used - it sits under the ring gear so the carrier can be placed more central.

Once the backlash is set accordingly with the side bearing adjusters, bolt everything up as it was when you got the diff out of the axle and you'll be looking at a steel SJ diff casing with 5.13:1 ratio differential gears!

Now go stick it back in that zook and get crawling! 

Specs

Pinion bearing preload 7.8 - 14.7 lb-in
Bevel Gear Backlash (0.004-0.006")

Note: the above backlash is for new gears, use the backlash measurements that you measured before dissasembly

Torque Specs

Side Bearing cap bolt 51-72 ft lbs
Drive Bevel gear bolt 58-65
Diff. case bolt 27-32.5
Side bearing adj. lock bolt 7-10
Diff carrier bolt 13.5-20

Credits

This article was written by Andy B

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