LET'S TALK ABOUT CASING MODIFICATIONS
Modifications can be a headache — we’re here to help.
Clearance for the differential carrier, crown wheel and crown wheel bolts should be checked by progressively fitting each part to the right-side case. Its finished appearance should be similar to the left side case when complete.
If you’re using the transmission in its 4WD state, that is the extent of your case modifications — move on to fitting the Subarugears ring and pinion and differential set up.
clearance the case
Shortening the AWD case to a 2WD case for Beetles, Kombis, Vanagons
As we are only using the 2WD part of the transmission, the casing can be shortened to 565mm length (plus 80mm length of shifter support tube that is placed over the top of the torsion bar). This should be performed on the later style center differential housings from 1999 onwards ( 8 bolt or TY754/755/758).
Earlier style centre housings (4 bolt TY752) are difficult to shorten effectively. These are identified by their square panel on top of the centre differential case. Newer centre differential casings are interchangeable with older style casings.
Alternatively, you can purchase our Subanose — one piece cast nosecone compatible with all 5 speed Subaru transmissions. No need to use a grinder or TIG weld, simply transfer the parts from your donor center differential housing and bolt it all on. The shape has been optimised to give the shortest possible shifter support length and maximum clearances.
Mark the cut-out line
9cm (3 1/2 inches) from the end with the cast bosses for the mounts. Do not mark all the way around — leave the base of the shift rod support tube unmarked and uncut. Carefully mark above and below the shift rod support tube. The castings are thin there and are easy to cut through.
Be very careful — there is a bolt just to the right of this round plate (gearshift interlock) that holds a ball and spring in place. Do not grind off the bolt. Do not grind down the flat mounting surface for this bolt or the tension that the ball and spring places on the interlock will be incorrect.
Note there are three holes to fill:
- Large hole with Subaplug.
- Hole on inside of shifter support shaft, filled with TIG weld, threaded plug, Devcon or Silicon.
- Weird-shaped hole on right hand side, filled with TIG weld, Devcon or Silicon.
After some finish grinding and flap disc work plus holes filled with Subaplug, threaded plug, TIG weld.
Complete shortened Subaru transmission casing
The casing needs to be welded in three areas :
- On the shift rod support.
- On the outside of the threaded hole that holds the oil splash catcher on the inside.
- In the area where the steel welch plug from casting has been removed.
Shorten the casing
The Subaru transmission has a small case breather built into the dipstick. Since the dipstick is no longer able to be used and the dipstick tube is sealed, a case breather should be built into the transmission in order to relieve pressure build up.
Subarugesars supplies a dipstick cover with each kit. This is a hi-temp silicon cover that ensures the oil flung up by the reversed ring gear does not get pumped out of the transmission. In order for the transmission to ‘breathe’ once the oil gets hot and expands/aerates, a breather hole in the casing is required.
The ideal location for the case breather is in the rear of the transmission case, as far out of the way from flinging oil as possible. The suggested case breather consists of one hole just above where the nosecone joins the main case — on the starter motor side. This area is a hollow casting area protected by the horseshoe.
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 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.
2. Install the collar
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.
Before re-assembling, you will need to swap the stub axle seals over from left to right. The factory stub axle seals are designed as a one-way seal to effectively keep oil inside the transmission case. You can see this in the image below with the diagonal ribs.
Failing to swap these over will cause the seals to ‘push’ oil out of the transmission case. You can either screw out the bearing cups with seals intact, screwing them back into the other side, or carefully pry the seals out of the cups and install them in the opposite side.
3. 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 and thus will need shims with thickness adding up to 0.5 or just below to bring the pinion depth to zero. A Subarugears Pinion Depth Tool is included in every gear purchase.
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 to zero.
4. Set the crownwheel mesh into the pinion gear
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.
5. Disassemble, assemble, disassemble
Disassemble the case again and smear bearing blue or yellow gear marking grease onto all surfaces of the pinion bearing. Smear bearing blue onto four 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.
6. Check the meshing pattern
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.