Assembly.

Here is the driven shaft after being pulled from the trans case :

On a front drive Subaru, or any other front drive longitudinal transaxle, the gears would be mounted directly to the pinion shaft.

This Subaru setup uses a concentric shaft layout and sends a slender front driveshaft through a hollow driven shaft to drive the front differential.

This shaft has the pinion gear on the end of it and is the one that will be replaced.

After the 27mm retaining nut, some washers and a bearing are removed from the end of the shaft so it can be pulled out.

Comparison shot between standard pinion shaft and reversed pinion shaft—note the reversed gear cut on the top one.

The main bearing that the driven shaft rotates on is mounted to the pinion shaft. If your bearing shows no signs of wear you can elect to re-use it.

The bearing itself is not a press-fit, the collar that holds it on is. The main bearing does not run on its own internal race, it runs directly on the shaft.

Installation of the collar can be done with an arbor and press. This shows a quick arbor made from aluminium pipe.

With the main bearing and collar in place, reinstall the smaller surface bearing that allows the vertical surfaces to move against each other.

For 2WD applications, install the Subaspool in place of the splined adaptor, 2 x washers & 1 x surface bearing at the rear of the pinion shaft.

Completed 2WD assembly with Subaspool installed, 27mm retaining nut torque and peened over.

If you have the Subaru factory tool available, set the pinion depth :

Fit the driven gear assembly to the right hand (modified) gearbox casing and torque the retaining plate up. Fit the Subaru factory tool over the gearbox casing with the dowels. Slide the gauge between the end of the crownwheel gear and the plate. This will show you how close your pinion gear depth is to ‘zero’. This picture shows that the clearance is 0.5. The tool can be ordered directly from here.

Adjust the pinion depth with various shims fitted between the shaft retaining plate and the housing. We re-fitted the two original shims to set the pinion depth close to 0.18mm, factory specs.

Next up, set the crownwheel mesh into the pinion gear by adjustment. Assemble both halves of the gearbox, with crownwheel and pinion in place. Screw both side bearing covers in and out as per the factory manual. The pinion shaft should turn easily with a tiny amount of slack when engaging the gears. Once you have met factory specifications, you need to double check the gear mesh with a physical test.

Disassemble the case again and smear bearing blue onto all surfaces of the pinion bearing. Smear bearing blue onto 4 teeth on each quarter of the crownwheel gear. Assemble the gearbox again and turn the pinion shaft a number of full rotations in both directions.

Carefully disassemble the case again and inspect the meshing patterns of the gears, using the factory specifications and illustrations as your guide. Make adjustments as necessary.

The meshing pattern on each gear should slide along the majority of the gear, engaging and disengaging before the ends where the teeth are weaker. Ensure the depth of gear mesh uses the majority of the tooth but doesn’t bottom out.