club.liberty.asn.au

Questions to support Change-Over Program

Okay, the determine the size of Thrust Washer there will need to be a procedure to go through on an exchange unit.
http://imgur.com/a/DaPLn

The first image exploded view (LHS) shows the Item 7 being the Thrust Washer Shim that needs to be selected when servicing the Centre Differential.
The first image (RHS) shows the standard factory procedure for selecting the shim thickness required.

The second image shows the installed position of the Centre Differential up against the nut on the Driven Shaft.
Following the procedure on the diagram a correct thickness thrust washer can be selected.
If the EXACT size could not be selected, a washer that would be +0.025mm to -0.025mm should be okay.

Now Question Time
An answer from the audience would be appreciated.
On the 6MT Centre Differential is a gear held on by a circlip.
See third image.
I cannot locate what this gear may mesh with?
The best that can be determined is that it forms a "paddle-wheel" type oil pump system to get oil up to the oil guide system shown in the lower RHS inset on the picture?
If anyone has had one of these diffs out, are you able to confirm the purpose for this gear?
Thank you!

"What is the Cost?"

There are four new seals per Differential Unit that need to be custom made.
(I have to buy a minimum quantity to support the project)

Presently, this is for the 38913AA112 Centre Differential.
The transmission code of the vehicle needs to be provided for confirmation.
I have not seen a 38913AA200 differential yet. If you require one of these I need to see one of these to confirm the details (first)

The Centre Differential will be rebuilt to a nominal 5kilogram rating.

An exchange rebuilt Centre Differential will be $325.00
There will be a refundable $100.00 shell deposit that will be refunded upon receiving your differential back in refurbishable condition.
Mailing will be by 5kg Prepaid Satchel both ways.

Customer would receive two Invoices (2 PayPal payment requests)
One would be for $360.00 (for $325.00 plus 2 x 5kg prepaid satchel $35.00)
Second would be for $100.00 shell deposit.

Customer would receive
Refurbished Centre Differential at 5kilogram rating, plus an unused return addressed prepaid satchel.

After the centre differential is fitted, the original diff would be repacked in the shipping packaging and returned using the return addressed prepaid satchel.

When the differential is received back in refurbishable condition the $100.00 shell deposit is refunded (Paypal deposit payment reversed)

Other ratings available upon request.
Mailing charges are as of the date of this post and based on prevailing AUSPOST rates.

For anyone reasonably local to you, could there be the option of a drive in, drive out service? For some extra cash of course...

Flat6Estate wrote:For anyone reasonably local to you, could there be the option of a drive in, drive out service? For some extra cash of course...

Drop off the diff and pick up next day, 24 hour turn-around, yes.

However, if you mean for me to perform the diff change, then sadly NO. Unfortunately I am not a licenced motor mechanic who may charge for such a service.

Then again, maybe for McDoof, if he drove all the way over? LOL

I plan to bring the first rebuild unit to the Olympic Park Meet on Sunday 29th November.
You can all take a look if you like.
Cheers!

I, and many others are set to appreciate your hard work and research. I may be in need of this in the near future.

A couple of questions:

Is there a difference in the internal damage problems with a CD that is only bining, compared to one that is binding and cluncking as well?

As the problem mostly occurs when the CD is hot, how did the shop you took it to test this?

Flat6Estate wrote:
A couple of questions:

Is there a difference in the internal damage problems with a CD that is only bining, compared to one that is binding and cluncking as well?

As the problem mostly occurs when the CD is hot, how did the shop you took it to test this?

Thank you, these are good questions.

First Part.
The damage is restricted to the fluid losing its properties and its temperature stability. Once the fluid overheats, the fluid becomes overly tacky, with too high a viscosity.
The viscosity then increases with temperature, hence the binding of the Centre Differential becoming more problematic when the gearbox heats up.
As you note in the second question, "the problem mostly occurs when the CD is hot".

When the Centre Differential is dismantled and cleaned. All the plates are inspected for damage, etc.
While I have seen pictures on the internet of other makes of viscous couplings where the internal plates are bent, I have not seem damaged internal plates on the Subaru Viscous Diffs, albeit that I have only torn down a few.

The Subaru viscous coupling design has an inbuilt flaw (my words) in that the circlip at the end retaining the coupling together will fail by dislodging under pressure before the internal plates become damaged.
At this point, the internals of the gearbox get damaged.

Only "binding" is a failing centre differential that is on its way to becoming worse and becoming "binding and cluncking as well".

Second Part.
Even though the "problem" becomes evident on the car when the CD is hot, the base level cold coupling torque already has increased above specification.
It should be noted that the CD unit provided by Brunsy3.0 was measured on my equipment when cold and before disassembly, to establish a base line.
The torque, measured cold, was about double that of the same diff once reassembled, and reassembled back to the same weight as prior to disassembly.

So, the Subaru gearbox specialist that the diff was taken to, were given the diff to test without telling them what it was.
The shop also sell "used differentials" that they have tested. So I trust that they are able to distinguish between a serviceable viscous coupling and a failing/binding differential unit.

Additional Part.
The design of the standard 5MT Viscous Coupling Centre Differential and the 6MT unit are essentially the same (one minor difference noted)
The internal components and working parts are the same, no difference, interchangeable.
So one question that I have been considering is "why the apparent difference in Spec-B 6MT Centre Differential failures compared to the 5MT units"?

My only response to date is to consider that the Spec-B cars can produce more power, have better suspension, more grip and can transmit more power through the centre differential on turns, as well as more likely to be driven spiritedly. There is nothing is the construction of the viscous coupling that would lead to differing service life?

Awesome write up man. Sadly i'm fairly sure mines starting to fail too. Been noticing a few clunks when turning after long drives.
You actually a mechanic or just a pro handyman? Feel like I could almost make my way theough a rebuild myself, only hard part would be the seals.

I started my trade as a Fitter-Machinist.
I have degrees in Mechanical Engineering and Electrical Engineering.
Along the way I have acquired Electrical Trades qualifications and Refrigeration & Air Conditioning Trades qualifications in addition.
Oh, and an MBA.
Cheers!

Seem like a bit of a life long learner. Got HVAC trade myself, and most likely starting a part time mechanical diploma next year.

BillyCorgi wrote:
My only response to date is to consider that the Spec-B cars can produce more power, have better suspension, more grip and can transmit more power through the centre differential on turns, as well as more likely to be driven spiritedly. There is nothing is the construction of the viscous coupling that would lead to differing service life?

I'm pretty dubious about this - plenty of pre-facelift GTs are caned regularly.
I'm more inclined to think it's related to the size and strength of the gearbox - and the heat retention. Large, thicker gearbox retains more heat and the centre diff wears more as a result? The environment it's in is different, so causes different results.

BillyCorgi wrote:There is nothing obvious (ed) in the construction of the 6MT(ed) viscous coupling that would lead to differing service life?

HardwareBoB wrote:The environment it's in is different, so causes different results.

Maybe?

Im surprised that there haven't been comments from anywhere in the world about a recall, or warranty extension on this part.
Seems that the average is around 150,000km. Seems like an unexpected life expectancy to me.

I have just ticked over 140,000km.
I am watching your words?

There are plenty of reports of 5MT centre differential failures on US forums.

Any scope for upgrades?
Eg cryo, peening, micro surfacing etc?