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The V8 Soarer was only available with an automatic gearbox and so they all came with a 3.916:1 diff ratio. Rumour has it that some came from the factory with a Torsen LSD (as everything was optional) but the only real way to tell is to check the axle code on the manufacturer's plate in the engine bay which will most likely say A01A which means it's an open diff and a Torsen LSD will be an A01B.

If you want slightly shorter gearing for quicker acceleration the Manual TT Soarer diff is perfect. It may seem like a small difference (actually 4.26% compared to the V8 diff) but you don't want something that's going to have you revving at 4000RPM on the freeway. When I swapped my standard V8 diff to a TT Soarer diff the change was subtle but noticable.

If you change diff ratio it will affect your speedo reading. In this case your speedo will read fast by 4.26% eg. if your speedo says 60km/h you're only doing 57.55km/h (57.55 x 4.26% = 60) which is cool as you'll be less likely to speed.... yeah right :-)

Everyone knows that open diffs suck when it come to getting power down because 1 tyre will usually lose traction and spin uselessly. Open diffs suck for another reason too - they break more often. Whenever anyone has broken a diff it's usually an open diff and more often than not it's what people call the spider gears that go bang after a long single spinner burnout.

My theory on this is that when 1 wheel is nearly stationary the spider gears are driving the spinning wheel whereas they're normally not turning that fast.

Here you can see the 2 little spider gears top and bottom which seem like the obvious weak point.

If you've got another theory on the weak open diffs feel free to let me know but no-one really cares about these ones.

What we really want is an LSD! Most people know in principle what the difference is between an open diff and an LSD but not many have come across a Torsen LSD. Torsen means Torque Sensing and is a mechanical piece of art that looks like an MC Escher concoction.

Here is the guts of a Torsen LSD. It works on the principle that a worm gear can drive but not be driven (ie the worm gear can drive another gear but it doesn't work in reverse). In a nutshell it acts like a regular open diff when the torque going to each wheel is the same, however if the speed differential between each side increases, the worm gears will lock and a proportion of the torque on the spinning side will be transferred to the non-spinning side by a fixed ratio. For example if the Torsen diff has a Torque Bias Ratio (TBR) of 4:1 then 4x the torque going to the spinning wheel will be transferred to the wheel with grip.

This all happens so smoothly and quietly that under normal circumstances you wouldn't even know you had an LSD unlike mechanical LSD's which can shudder and clunk.

The only downside is that if the spinning wheel is completely in the air there is zero torque so, multiply that by the TBR and you get 0 torque going to the gripping wheel. This is why the Torsen II was produced which has an internal preload so some torque will always be applied to each wheel enabling the TBR to be effective.

Normal mechanic LSD centers using clutch packs can be obtained from the likes of Cusco, KAAZ or TRD among others. These can be noisier but those that have one swear by them:

" I Love my Cusco LSD. For Track Days it is an essential tool; no more wheel spinning coming out of corners under full throttle, which obviously makes the car feel a lot more sure footed. I don't find it noisy at all for street driving; it only chirps and crunches when I'm doing tight turns in carparks and such. No where near as bad a Fully Locked Racing Diff' but very similar. It's strong as an Ox, loves to do Big Loooong Burnouts with both wheels and doesn't mind going from 60kph in top gear, BANG into 1st and away !!!! How I got by without my Cusco for all those years I will never know"

YES - The non-turbo JZA80 Supra (SZ) diff (for auto or 5 speed manual) is identical to the TT Soarer 5 speed diff which has a 4.083:1 ratio. This ratio is labelled as 01 for Supras so a compatible Supra Torsen diff is an A01B.

MAYBE - Auto TT JZA80 (RZ) diff. This has a ratio of 3.769:1 so is taller than the standard V8 Soarer diff but if you're going for forced induction (supercharging or turbo charging) the extra engine torque may warrant a taller final drive. If you find a Torsen diff but the ratio is not what you want, you can always have a diff/gearbox specialist swap the pinion and ring gear with your existing diff.

NO - The diff from the 6 speed JZA80 Supra (RZ) is NOT a bolt in option. Firstly, there is a huge gearing difference as the 6 speed supra diff has a 3.2 ratio so would be far too tall to use with a Soarer gearbox. However, if the V160 6 speed gearbox is going in then this diff should be fitted too but if that's the case extensive work will be required anyway.

Secondly, it's physically too big. Below left is a B-series 6 speed Supra diff that has a larger ring gear and a Soarer diff on the right. It is so big the Supra has 1 drive shaft shorter than the other because it is offset to the side. Here you can see how much wider the Supra diff is compared to a Soarer diff.

It's not hugely apparent but the right side of the Supra diff (black) in the bottom shot is offset to the side requiring a shorter drive shaft on that side compared to the other.