This photo shows a ST165 front (and centre) differential. This example is out of a 1987 Gearbox (without viscous coupling) although the later gearboxes will have an assembly effectively identical. Note that the 16 axial bolts holding the assembly together are not fitted. This photo also shows the location of the ring gear, one of the parts swapped to change the final drive ratio. The two taper bearings for the unit are visible as well as the splines for the diff lock mechanism (which viscous gearboxes don't have)
This photo shows the differential unit partially separated. Visible is the front differential (ie between the front wheels). This differential directs drive to the front left wheel via the gear visible in the housing on the left, and to the right wheel via the long thin shaft extending out to the right.
And with the front differential pulled forward you can see the centre differential squeezed in behind. This is really tight packaging! The centre diff drives the front diff assemble (as seen here) and the splined shaft extending to the right (which goes to the transfer).
As you can see there are quite few components in this section of the gearbox. However with the correct grade oil (changed as required) there is no reason why the gearbox (except the synchros ;-) won't last the lifetime of the car.
These photos show the Torsen (Torque Sensing) rear limited slip differential. This was fitted to all Japanese spec ST185 and ST205 models, while all ST165 models were fitted with an open diff. It has been reported that *some* US spec ST185 also came with the Torsen diff, however that is pretty hazy as to which.
You can't tell which type of diff you have by jacking up a rear wheel and rotating it (like you can with a clutch type LSD). A Torsen diff acts exactly the same as an open diff. If you jack the rear of your car up and turn a wheel, if the opposite wheel spins in the same direction you have a TRD (or other) clutch type LSD.
Note that *all* GT-Fours use the same rear diff ratio and casing, therefore the diffs are a direct swap.
Also the Torsen diff does not use clutch plates therefore no special LSD oil needs to be used. Just use normal diff oil, they don't give too much trouble.
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