6MT Centre Differential Rebuild Project

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Re: 6MT Centre Differential Rebuild Project

Postby Kimmo » Sun Jan 24, 2021 10:22 am

BillyCorgi wrote:
Yowie wrote:It's a viscous circle.


https://www.amazon.com.au/Viscous-Circl ... 1497637716


Hah! Instead of a rimshot we get our minds blown; love your work.

Read heaps of SF but never much Piers Anthony, been meaning to check him out more.

BTW, while we're pimping SF, Liu Cixin's Three-Body Problem trilogy is an absolute masterpiece, of the most epic scale imaginable. Although I actually gave up for a bit at first; it took a couple of hundred pages to really get going... but definitely worth the initial slog, after that I couldn't put it down. Reading it as an epub on my phone, putting it down was bloody impossible.

I hope the Netflix series does it justice...
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Sun Sep 12, 2021 4:32 pm

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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Sat Feb 12, 2022 1:21 pm

Not all Centre Diffs with gearset clearance are good......
However all Centre Diffs without gearset clearance are bad.


Okay, time for an update.
Recently, Gavin contacted me with the question "Is there a simple way to see if (my centre differential) is ok?
The only definitive way is to pull it apart, by which time it requires a rebuild anyway?

The viscous coupling centre diffs fail in three basic failure modes, all associated with the degredation of the viscous silicone damping fluid.

The most common failure mechanism is failure of the viscous fluid with expansion.
In this failure mode the viscous fluid goes "off" due to overheating and the fluid expands in volume in the process.
The expanding fluid causes the differential side gear to move axially and close up the gearset clearance.
The lack of gearset clearance binds up the diff.
BANG-BANG-BANG-BANG goes the failing centre diff on slow tight turn when hot.....

Another failure mechanism is pure failure of the viscous fluid.
The fluid just goes bad due to overheating and the centre diff binds up when the fluid gets hot.
The fluid begins to vulcanise into silicone rubber and separates into heavy and light fractions.
The heavy fractions bind the diff when the temperature gets hot.
BANG-BANG-BANG-BANG goes the failing centre diff on slow tight turn when hot.....

The last failure mechanism is by vulcanisation for the silicone fluid.
In this mechanism the forming silicone rubber plates onto the viscous plates and does not allow the plates to slide past each other within the fluid.
The rubber coating on the plates acts as a brake and causes the centre diff to bind up.
BANG-BANG-BANG-BANG goes the failing centre diff on slow tight turn when hot.....

The centre diff can exhibit one or more of these failure modes.

This leads to the comment.....
Not all Centre Diffs with gearset clearance are good......
However all Centre Diffs without gearset clearance are bad.


One day, while I was stripping centre diffs for rebuild Mrs Wife came out and asked "what is that peculiar smell?"
To which I replied "that, my dear, is the smell of money......."
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
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Re: 6MT Centre Differential Rebuild Project

Postby Ric » Tue Feb 15, 2022 2:23 pm

BillyCorgi wrote:...
One day, while I was stripping centre diffs for rebuild Mrs Wife came out and asked "what is that peculiar smell?"
To which I replied "that, my dear, is the smell of money......."

Love it :rotfl:
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Re: 6MT Centre Differential Rebuild Project

Postby bigBADbenny » Wed Feb 16, 2022 9:37 am

Adding some boron nitride aka white graphite to the silicone fluid might be a weird and unnecessary experiment?
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Sat Apr 02, 2022 3:45 pm

Someone is going to win the CorgiWerx Golden Ticket!

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Last edited by BillyCorgi on Wed Apr 20, 2022 3:06 pm, edited 1 time in total.
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Wed Apr 20, 2022 3:05 pm

Someone has the CorgiWerx Golden Ticket!

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Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
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Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
Want a custom built Brake Cylinder Stopper? viewtopic.php?f=6&t=31321
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Re: 6MT Centre Differential Rebuild Project

Postby nvmylh » Thu Apr 21, 2022 9:58 am

What did they win? Ticket to the mysterious diff factory filled with magical midgets?
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Re: 6MT Centre Differential Rebuild Project

Postby Yowie » Thu Apr 21, 2022 9:07 pm

:lol:
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Thu Apr 21, 2022 9:43 pm

nvmylh wrote:What did they win? Ticket to the mysterious diff factory filled with magical midgets?


Heidi is not a midget, she is a normal size dog on short legs.

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Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
Get your Gear Shift Rejuvenation Kit viewtopic.php?f=68&t=31240
Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
Want a custom built Brake Cylinder Stopper? viewtopic.php?f=6&t=31321
Need to hire a Guard Rolling Machine? viewtopic.php?f=6&t=31899
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Wed Aug 24, 2022 8:11 am

"Is It a CorgiWerx?"

The Chief Corgi has recently retired from his day gig and is now concentrating solely on the CorgiWerx venture ‘Supporting the Subaru Enthusiast Community’. The CorgiWerx mission has always been to support the Subaru community with a better-cost replacement part alternative to the high-cost non-serviceable OEM part.

With an IQ somewhere between 145 and 150 the Chief Corgi has over 45 years of valuable engineering experience, of which 35 years have been in product design, product development, original equipment manufacturing in both the automotive Teir 1 supplier and precision machine manufacturing space. In that time he has gained degrees in Mechanical Engineering and Electrical Engineering, a graduate diploma plus a Masters of Business Administration, as well as trade qualifications in Fitting & Machining, Electrical Trades, and Refrigeration & Air Conditioning.

Being retrenched in 2015 the Chief Corgi spent two years unemployed during which time he commenced a study into Subaru Centre Differentials and launched CorgiWerx. After having a centre differential fail in one of the Subarus in the family fleet and reverse engineering the component this post commenced on Thursday September 24, 2015 to record and share the journey. The first rebuilt centre differential was shipped in December 2015.

CorgiWerx developed their own intellectual property which includes, among other things.....

The supply source for the silicone damping fluid used in the centre differentials
The grades of damping fluids for the various torque settings of the centre differentials
Sourcing of best cost components required for the centre differential refurbishment process.
Calculation of the damping fluid charge for each centre differential
The technology to measure the gearset clearances within the centre differential
Statistical process measurement to determine the statistical 'Mode' of the 'factory' clearance setting
The technology to adjust the clearances to desired clearance setting
The technology the ensure that the gearset clearances are maintained during assembly to guarantee the correct clearances through the assembly process
The technology for stacking the viscous coupling plates to prevent 'hydraulic-lock' during final closing operation (which prevents the closure cap from seating)
Design and manufacture of the special tooling used in the manufacturing process
plus more

CorgiWerx listened to their customers, interpreting what was the 'want' the customers were seeking, interpreting that into a specification, and engineering that specification into the design and process controls to achieve the 'desired' outcome.
During his professional engineering career the Chief Corgi remembers clearly the requirements from the experts; Guaranteed Design and Guaranteed Process.
These philosophies are used to ensure that every CorgiWerx Centre Differential is assembled to consistent quality and to tighter tolerances than Subaru's own product.

So, if you are fitting to your Subaru, or are offered for your car, a rebuilt/refurbished centre differential , ask yourself "Is It a CorgiWerx?"

Present rebuild level stands at 1.074 units as at 31st July 2022
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
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Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
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Re: 6MT Centre Differential Rebuild Project

Postby subyroo » Wed Aug 24, 2022 12:00 pm

Hi, from one Peter to another. :lol:

Congratulations on your milestone. :good:
Thank you for your support to the Subaru community.
Pedro

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MY03 XS Forester (owned for 13yrs.)
Man blames fate for other accidents but feels personally responsible for a hole in one.
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Mon Aug 29, 2022 6:32 pm

Well again, once more, in addition to the past occasions, we continue to find centre diffs where someone has attempted an overhaul of the unit and charged it with gear oil.
Using gear oil does not work. It cannot handle the heat and burns,; it does not have the required lubricity and chops out the metal components; it does not have the required extreme pressure properties and tears up the thrust washers; it does not have the required viscosity to provide the OEM torque rating,

Someone is out there providing a sub-standard workmanship creating a sub-standard non-oem specification product and relieving their customers of their hard earned money.

In the past month we openned a returnd Spec-B 6MT centre diff and found that someone from the blue & white apron brigade had performed a dodgy refurb and converted it to an open diff. The internals had been spaced out with a collection of dodgy parts from other centre diffs. Contacting the owner we were informed that the previous owner of the car had had the centre diff replaced in Albury and it was reported to be an "OEM-plus".
So an "OEM-plus" is a dodgy open diff conversion that will destroy the handling characteristics of the car and likely lead to a Spec-B that will pick up and spin one wheel uncontrollably mid corner or during vigourous acceleration. Well FMD.

There is only one CorgWerx.
CorgiWerx are 'The Subaru Centre Differential Subject Matter Experts'.
If you are going to replace your centre differential in your Subaru ask yourself "is it a CorgiWerx?"

STOP PRESS
Just openned up a 5MT unit just now (Serial Number RM255) which is engragve on the cap ATJP09/20. (or mabe ATJP 09/10) and found it to be filled full of grease. Well FMD^2
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
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Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
Want a custom built Brake Cylinder Stopper? viewtopic.php?f=6&t=31321
Need to hire a Guard Rolling Machine? viewtopic.php?f=6&t=31899
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Tue Aug 30, 2022 10:16 am

After overhauling over 1,000 Centre Differentials you get to see many things with sufficient quantity to detect issues and trends. On thing we have often seen is the centre diff with a whitish-green sludge in the differential gears. We believe that it is the brand of gearbox oil or an additive used in the gearbox oil. It is definitely not G70 additive, we believe that it is a brand of shock-resistant gear oil.

What we have found is that this particular oil has a high quantity of suspended solids intended to reduce friction or possibly lessen the effect of shock impacts. We cannot tell.

What we have found is that the solids get packed into the gear teeth of the centre diff differential gearset by the action of the gearset meshing. This causes the gearset clearances to close up leading to premature binding of the centre differential.

CorgiWerx DO NOT recommend the use of this type of gearbox oil with high suspended solids with the Subaru Centre Differential (manual transmission).
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
Get your Gear Shift Rejuvenation Kit viewtopic.php?f=68&t=31240
Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
Want a custom built Brake Cylinder Stopper? viewtopic.php?f=6&t=31321
Need to hire a Guard Rolling Machine? viewtopic.php?f=6&t=31899
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Re: 6MT Centre Differential Rebuild Project

Postby BillyCorgi » Fri Sep 02, 2022 9:53 am

There are three basic models of the Subaru Centre Differential.

Ths 5MT Model 38913AA10X of which there are three sub-varients 38913AA100, 38913AA101 & 38913AA102
The 6MT model used in Spec-B gearboxes of which there are two sub-varients 38913AA112 & 38913AA200
The 6MT model for Cable Shift gearboxes 38913AA230

For the 6MT Spec-B units 38913AA112 has the drive gear fitted for the internal oil pump & 38913AA200 has had the gear deleted for the updated gearboxes without oil pump

All the 5MT models are interchangeable, they will all work in any Phase 2 5-Speed gearbox application
38913AA100 and 38913AA101 has the 'spiral circlip' - which is reknowned for dislodging from the body of the centre diff and jumping into the transfer gears, usually at great cost to the owner.
The horrible spiral circlip was deleted with the 38913AA102 version and the 'C-type' circlip used in the 6MT centre diffs was introduced on the 5MT units.
Like with the EJ25 NA head gaskets, it took Subaru a long time to recognise that the design had an expensive failure mode issue and introduce an effective known countermeasure
See the pictures below.
The centre diff is fitted with the C-Type circlip and comparison between the spiral circlip (left) and the C-Type circlip (right) is shown below.

CorgiWerx only build their 5MT centre differentials to the 38913AA102 specification with the C-Type circlip.
All CorgiWerx centre differentials have the C-Type circlip.

Image
Get your Short Shift Adaptor viewtopic.php?f=68&t=30525
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Get your Centre Differential Rebuild viewtopic.php?f=6&t=31089
Want a custom built Brake Cylinder Stopper? viewtopic.php?f=6&t=31321
Need to hire a Guard Rolling Machine? viewtopic.php?f=6&t=31899
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