Installing HexMods Center Differential Bulletproof Bushings

[tylerwade17]

Search for part 33257AA060. It's about $210 here: http://subaruonlineparts.com/oemparts/33257AA060

 

Thanks a lot!!!

[firehawk618]

Bumping up a GREAT how to thread.

 

ClimberD. Thanks for the detail and pics. Mine has blown *90% sure* so I will be pulling mine soon to see what all is damaged.

 

BTW, have you encountered blown up center differentials on these 5eat's? If so what normally gets destroyed?

 

I have sourced a good used center diff. Looks like it's all there except friction and steels. I am hoping mine are either re-usable or easy to source.

 

Also, since I will likely have to re-use my frictions do you know what the specs are because wouldn't my friction / steels with a different drum require different shims?

 

Thanks in advance!

[firehawk618]

I'm going to add one thing I battled with during this how to.

 

The tail shaft has a piston assembly that stays in it. On the outer ring of that there are teeth that MUST line up with the clutch pack housing *not sure what that part is called*. It's the part where you install the frictions and steels. Look in your tailshaft prior to install. It's the outermost ring of that piston. That ring rotates. Those teeth must magically align or you'll get the tail all the way on but the last 1/4". It'll give the illusion that the dowels are holding it up but they are not. I had to pull my tail off 3 times before I figured this out.

 

I rotated it at random and this time it all fell into place.

 

That part is a royal PITA!

 

Sidenote: I didn't have to pull my DP. Only the cat-back section. This allowed the exhaust to drop enough and I was able to do the work. I do have an aftermarket DP though.

[firehawk618]

Carnage pics and a pic of that piston to come.

[ClimberDHexMods]

Many of you have asked, yes I am still selling these

Unfortunately often times it is in response to a 5EAT center diff that has already broken

[whitrzac]

Bumping this up again. These pictures would have save ~2hrs of **** today.

 

IDK what the 'new style' one piece tailhousings look like, but if you have a 2 piece...

 

You can pull the diff by taking off 1 tail section or both.

 

If your trying to do both, like the fsm recommends, take ALL of the bolts out, not the 10 that the fsm shows.

 

Go slow on them, years of steel bolts in aluminum can cause issues....

 

 

This can be done under the car. Make sure to have a clean workspace setup to pull the bearings/install the bushings.

 

After doing one, I think I could have a car from running to running in ~2-3hrs...

[trini legacy]

After doing this mod has anyone carried their car to the strip and launched it a few times? What I'm trying to do is get a feel of how much of a difference will this mod make. I recently launched my car a few times, it worked well for a few weeks but on the last launch a few days ago I ended up damaging the transfer shaft that fits inside the center diff. A few teeth on the gear was partially stripped off but the bearings in the center diff seemed ok. Would the bulletproof bushings have helped to prevent this?

[ClimberDHexMods]

After doing this mod has anyone carried their car to the strip and launched it a few times? What I'm trying to do is get a feel of how much of a difference will this mod make. I recently launched my car a few times, it worked well for a few weeks but on the last launch a few days ago I ended up damaging the transfer shaft that fits inside the center diff. A few teeth on the gear was partially stripped off but the bearings in the center diff seemed ok. Would the bulletproof bushings have helped to prevent this?

 

Good question.

The bulletproof bushings flex less than the stock needle bearings, and have a tighter tolerance. The tighter tolerance produces a visibly tighter gear engagement. This results in an increase in the amount of abuse a center diff can handle before it fails. The mode of failure for the center diff is fatigue, not the common mode of shock.

The more permanent solution is to have the center diff gears treated with Cryo and/or REM-ISF. Cryo increases the gears' resistance to fatigue, and REM smoothes out the course tooling marks on the gear teeth, thus reducing hot spots. I sell these new OEM treated gear sets, but I only have the input shafts in stock. I am having new input shafts and planet gears treated through both processes, but they take a long time to complete, and delays are common. However, treated gears + bulletproof bushings are your best way forward long term if you plan to continue drag racing the cars.

 

Summary: Center diffs do rarely fail with bushings (though the failure rate is significantly reduced). Center diffs have never to my knowledge failed when the gears themselves are treated with a minimum of cryo.