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Subaru Gears Product Review and assembly procedure

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Setting Pinion Depth:

I covered this before, but this time its a little more in depth.

This is one part of this project that is a lot of repitition. Its not hard, just a lot of rinse and repeat.

This is one of your pinion shim. The ones I have only come in .010", and .005"
pinion depth (1).jpg

Here is where they go. They only fit one way, and they are fragile. They must be handled with care when the pinion shaft is placed into the right hand transmission case half. The split in the shim will be facing down when it goes into the right case half.
pinion depth (3).jpg

These are the two bolts (12mm) that must be snugged down each time the pinion depth is checked.
pinion depth (4).jpg

The process goes like this. Place the pinion shaft into the right hand case half without any shims installed. Tighten at least one of the bolts down. Use your pinion depth tool provided by either Subaru, or by Subarugears (comes in the kit). Measure the pinion depth with the tool. This is total thickness of shims you will need.

Use a pair of dial calipers (not digital ones; The digital calipers can read with a lot of error when they are off, or have low batteries. You wont know until its too late.) Measure all of your shims. Combine your shims to equal the total depth read on the pinion depth tool.
Now carefully install them onto the pinion shaft and place the shaft with the shims on it back into the right hand case. Re-tighten the two bolts (make sure the bolts go through the shims), and take another reading. If you've zero-ed out the pinion and get a zero reading it will look like this:
pinion depth (2).jpg

If you get this result, your done with setting the depth. If you get a plus or minus reading from zero, repeat this process by adding or removing shims until you get zero.

Next, Ill cover adjusting the the backlash.
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New member
Just a note:
I just received a response from Todd @ subarugears. Another thing I was not aware of, is by going with a Subaru Transmission, and Subaru engine you get an additional 2.5" of oil pan ground clearance, as compared to using a VW transmission and a Subaru Engine with an adapter plate. (EJ series engines).

Brett Proctor

Well-known member
Just a note:
I just received a response from Todd @ subarugears. Another thing I was not aware of, is by going with a Subaru Transmission, and Subaru engine you get an additional 2.5" of oil pan ground clearance, as compared to using a VW transmission and a Subaru Engine with an adapter plate. (EJ series engines).

If your getting an additional 2.5" ground clearance that means the engine will be 2.5" higher in the engine compartment ,Right?

looking at how my engine sits,your going to have a big hole in the top with the engine sticking out of it, or I'm I missing something.


New member
Im not sure, It could be due to the angle, and or where and how it sits on the frame horns. There are also two different locations on the mount. one is for single cam engines, and the other is for dual cam. If it becomes an issue, I may be able to use the other hole.
But then again, I have already planned on redesigning the rear deck anyway.:D







New member
Setting the backlash

This is the part of the build that isnt hard, but is tedious. It involves a lot of assembling and dissassembling of the transmission and repeating steps until your results come out correctly.

Setting the backlash (1).jpgFirst the retainers must be backed out until the base between the ribs is flush with the case. Remove the bolt and retainer and back them out on both case sides.

Now, the transmission must be assembled on its left (starter hole) side.
Setting the backlash (2).jpg Setting the backlash (4).jpg Here in this photo you can see the pin(s) in the case bearings, and the hole in the bearing(s) on the input and pinion shafts.

Setting the backlash (3).jpg This is another tricky little guy. On the back of the input shaft there is a piece of metal with two bent tabs on it. When you insert the shaft make sure this is free of the shift shoe (looks like a big C). Otherwise it will get messed up.

Setting the backlash (5).jpg Here the input and pinion shafts are now installed. The pins have been aligned with the holes in the carrier bearings.

Setting the backlash (6).jpg The shafts are in their proper place, and the metal end on the input shaft (left) is free of the shifting shoe.

Setting the backlash (7).jpg
Install the lower two bolts through the shims and plate of the pinion shaft. Snug them down tightly.

Setting the backlash (8).jpg The input shaft bearing is properly seated and there is no clearance between it and the case. Do a visual check after you feel it snap in.

Setting the backlash (10).jpg Once the input and pinion shafts are installed, install the ring gear and central diff into the case teeth side down. Be careful to not pop out the spring retainer in the output shaft seal.
Now install the other case half. Be careful and place it rear down first to ensure you dont crush the shims at the back. when the output shat is poking through its seal, and the shims are in place and havent been smashed, wriggle the case halves together, and start installing all of the bolts. Tighten them down just like you would for a final installation (though you dont need to torque them).

Setting the backlash (16).jpg Using your wrench, follow the proceedure in the manual, but remember to reverse the directions. Since the diff is on the other side now what is up, is down, what is right is actually left in the directions.

If you prefer I have written out a pre-flipped set of directions taken from the manual.

Here they are:
[FONT=&quot]6) Tighten the RH retainer until contact is felt while[/FONT]
[FONT=&quot]rotating the shaft.
[FONT=&quot]Then loosen the LH retainer.[/FONT]
[FONT=&quot]Keep tightening the RH retainer and loosening the[/FONT]
[FONT=&quot]LH retainer until the pinion shaft can no longer be[/FONT]
[FONT=&quot]This is the Zero state.[/FONT]
[FONT=&quot]7) After the zero state is established, back off the[/FONT]
[FONT=&quot]RH retainer 3 notches and secure it with the lock[/FONT]
[FONT=&quot]Then back off the LH retainer and retighten[/FONT]
[FONT=&quot]until it stops.
[FONT=&quot]Rotate drive pinion a few times.[/FONT]
[FONT=&quot] Tighten the LH retainer 1-3/4 notches further.
[FONT=&quot]This sets the preload.
[FONT=&quot]Finally, secure the retainer with its lock[/FONT]
[FONT=&quot]Turning the retainer by one tooth changes the[/FONT]
[FONT=&quot]backlash about 0.05 mm (0.0020 in).[/FONT]
[FONT=&quot]8) Turn the drive pinion several rotations with ST1[/FONT]
[FONT=&quot]and check to see if the backlash is within the standard value with ST2, ST3, ST4 and ST5.[/FONT]
[FONT=&quot]ST1 499787700 WRENCH[/FONT]
[FONT=&quot]ST2 498247001 MAGNET BASE[/FONT]
[FONT=&quot]ST3 498247100 DIAL GAUGE[/FONT]
[FONT=&quot]ST4 499787500 ADAPTER[/FONT]
[FONT=&quot]ST5 498255400 PLATE[/FONT]
[FONT=&quot]0.13 — 0.18 mm (0.0051 — 0.0071 in)[/FONT]
[FONT=&quot]9) Adjust the tooth contact between front differential and drive shaft. [/FONT]
[FONT=&quot]<Ref. to 4AT-105, ADJUST-[/FONT]
[FONT=&quot]MENT, Drive Pinion Shaft.>[/FONT]

Setting the backlash (19).jpg Here the backlash has been adjusted, and within tolerances. Technically, its good, but its always a good idea to get your backlash somewhere in the middle of the tolerance in this case between .013, and .018mm.

Think were done? Nope,... now its time to take the whole thing apart again!

Now that the pinion depth is set to zero, and the backlash has been adjusted, Its time to check the gear mesh with prussian or gear blue.

Take apart the transmission. Only take out the right case half two bolts for the shim retainer.
conversion step (8).jpg as seen here in an earlier step.

Leave the shafts in the left case half. Take out the ring gear and diff.

Using prussian blue paint the blue grease on the teeth of the ring gear in the 12, 3, 6, and 9 o-clock positions. Paint the front and back of 4 consecutive teeth.
20150129_183935 (800x600).jpg

Next paint the prussian blue on the tip of the pinion shaft.
20150129_183945 (800x600).jpg

Now reassemble the transmission, just like before.
Once all the bolts are tight, spin the back of the pinion shaft (suba-sleeve is on it) several full rotations in both directions. Then take the transmission back apart. and check the mesh contact pattern.

20150129_185858 (800x600).jpg
Here you can see that my pinion is too deep, and only grabbing at the fron of the teeth. You can tell by the thinner grease that looks like a mich brighter blue. It can also be seen partially on the non greased teeth. The excess grease was wiped off only at the front of the teeth, not in the middle, or the back.

So at this point, rinse and repeat.
In this case I need to add a shim to the pinion shaft. The back off the side retainers and reset the back lash. Then recheck the mesh again with prussian blue.

Each time you adjust the shims on the pinion shaft it will change the backlash. So those steps must be repeated until you get it worked out. Its can be a pain, but necessary to ensure the transmissions life.

20150129_185819 (800x600).jpg The marks left on the teeth should be along the majority of the center of the teeth, not their edges.


Excellent writeup. Could I trouble you to circle items that you are describing in the photos. I can't make out which pin and hole needs to be aligned on the shaft. Also if you could point out the C-clip that needs to be positioned certain way?
Thanks for taking the time and generating this step by step instruction.


New member
Here ya go.

Setting the backlash (2).jpg
The pins are in the case in the bearing seats in the bulkhead between the main diff area and the gear set. You'll see them when you crack open the case. Also the pins can fall out while your working on the cases, so be sure to not lose them.
Setting the backlash (4).jpg

Setting the backlash (6).jpg

No problem*thumbs up*


New member
Today I spent most of it working on getting the gear mesh correct.

I got some weird results last time, so I started from scratch and re-zero'ed the pinion depth.
I needed 3 .010" shims to reach zero.
3 shims 3x .010 (3) step one zero pinion.jpg 3 shims 3x .010 (2) step one zero pinion.jpg
The first test was with .030" worth of shims.
This test came back with too much depth, so according
to the book it said I needed to remove shims.

guide (605x393).jpg Seen here.

3 shims  .005 .010 and .010 step two (1).jpg 3 shims  .005 .010 and .010 step two (2).jpg
Next at .025" worth of shims.

2 shims .010 and  (1) step three.jpg 2 shims .010 and  (2) step three.jpg
Then at .020" worth of shims.

proper contact.jpg
This is an example of proper contact on both the
front and the backs of each tooth.

So you can see in the last set, that .020" worth of
shims is still off a tad. Perhaps tomorrow Ill have the
gumption to get out there and finish it.

Each time the pinion depth is changed, the backlash
and gear blue must be redone, and a full dissassembly and
reassembly of the transmission is required each time.

Rinse and repeat until you get it right....*thumbs up*
Tedious, but necessary.


Would be interesting to know how your final shim stackup compares to the zero set point predicted by the tool.


New member
Im pretty sure the zero point is only there to get you into a starting position.

Especially since you can only use no more than 3 shims at any time.

*A note from Subarugears.com The gear backlash must be checked without the subaspool installed. Only the nut on the end of the pinion shaft. Otherwise, a false backlash reading will result. This is due to the 1-5 gearset giving conflicting results in the reading.*

The manual shows a tool called ST
498427100 stopper (page 26) This does the same thing as the subaspool, however you will be reading the backlash of the 1-5 gearset as well, not just the pinion and ring gear. By removing the subaspool and putting the lock nut on the shaft when you test the backlash it will be between those two components only, making the reading very accurate.

Im finding out now if removing the input shaft and gearset will do the same thing as removing the subaspool. Id prefer not to undo what I have already had done if possible.
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New member
OK its been confirmed. At this point if you need to adjust your backlash, do not install the input shaft during the check. It is equivalent to removing the subaspool, and using only the nut on the pinion shaft. This way the true measure of the backlash can be verified.

When everything is correct it is time to seal it up, and finish the project.*thumbs up*


New member

I took a trip to the local transmission shop in attempt to see if I could rent the pinion adjusting tool from them for this job. Turns out they do the same thing I was having to do,.... Make one.

They handed me a scrap servo valve from a pile of auto transmission parts, and after paying homage to the blood gods (see blood gods thread), my pinion adjusting tool was finished.

I simply ground off the oring slot around the lip, then marked the notches with a sharpie and ground them out. The pinions dont need to be really wrenched on, so this worked out perfectly.
pinion adjusting tool (3) (648x614).jpgpinion adjusting tool (4) (800x733).jpg

I found my contact patch was always coming out the same, despite many tries to get the gear mesh correct. Finally I went to the local tranny shop and took my phone to show them the photos. My backlash was spot on at .005" or about .15mm.
I have been keeping them aprised of this project, and they have been very interested. After seeing this contact patch, they said it was spot on. Despite the contact patch being a bit toe'ed (coming off the inner edge of the tooth) it isnt starting on or beyond the inner edge. Once the load is transmitted it will shift the contact patch further to the middle of the tooth. So the shop owner gave me a thumbs on it, and off I went to finish up the assembly.
final gear mesh (1) (605x800).jpgfinal gear mesh (2) (666x800).jpg
NOTE: when doing backlash, do not put gear blue mesh grease on first. Get the backlash, then do the mesh check.

Getting the shift rod in correctly can take a bit of fiddling, but once the nose cone was on, I verified all gears shifted. All sealed up, torqued, and waiting to be attached to an engine now.
fini (1) (800x763).jpgfini (2) (399x800).jpgfini (3) (800x456).jpg

In the photo on the right you will see two open bolt holes to the left of the stub axle. They do not go to anything, So the lower one can be drilled through and a 10mm (14mm wrench size) bolt and washer can be added there for a fluid level inspection hole.

Anyway, this concludes the SubaruGears product review, and procedure. I hope this in some way helped you visualize how this is done. Todd's a great guy, and has endured hundreds of emails from me. Hopefully, there will be a test drive soon.

Now Im off to start work on WRX 2.0 turbo engine....*rock on*
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Thread now locked since the how-to is complete, by request. Any additional questions can be asked and posted in the forum.
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