Is it possible to distinguish a standard 4kg centre diff unit from a 12kg unit? I have a reply to a "wanted" ad elsewhere on the forums but would like to ensure the parts are what we think they might be.

Cheers,
Jay Storm

 

I think you'll find the uprated Prodrive ones are 20 KG and it is written on the outside with etch pen. Quite a rare thing.

Never heard of a 12 Kg one. It's not a listed Subaru tension, to my understanding.

David APi

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12/20....

Autospeed centre VC article

I did some checks when MRT used to sell the centre diffs and at the time the 12Kgm was only available in the earlier 'openable' design not for 99MY on.

Further research (not sure where I found it now) suggests all non DCCD STi are 20Kgm.

You may find http://www.japanparts.com/db/partsli...maker=&volkey= handy as well, if it doesn't open my search just go through the selector picking diffs and STi

Simon

 

Thanks for the reply. I'm trying to source a 12kg center diff to put in place of the standard 4kg. I ran a Cusco Tarmac center diff this race season and really liked the way it transformed the car. However, I am losing a little too much time off the line due to wheel spin (with a non-turbo EJ22) so my AWD advantage has been pretty much reduced to extra weight and drivetrain loss. I'm hoping the 12kg will be a bit more solid off the line yet not push too much when it's time to pour it into the turns.

Jay Storm

 

Thanks Simon. I am currently using the phase I style trans case(s), so the 12kg diff would be a drop in for me.

I emailed japanparts about a possible trade (for the Cusco unit) ....language barrier may have caused mis interpretation, as I was told to simply order one and choose my shipping method....then wait approximately 2 months.

 

David,

Jay is asking about this diff:


I can read GK760 on this (flashlight of the camera takes out the 7)
If anyone can tell by this picture, or one from another angle, if this is a 4kg, 12kg or 20kg that would help!

 

japanparts don't sell used kit, so can't see they would be interested, besides with carraige cost just not worth it I think.

The Cusco has a nice torque split but no LSD element, so yes, not good, why not go DCCD, or use a DCCD diff (so rear biased torque split) with the LSD element rebuilt (more preload and make a 1 or 1.5 way) to act as a plate diff?, they can also be rebuilt to a sprag clutch type arrangement with perm RWD and only FWD when the rears starts to slip, although its a bit abrupt!

Otherwise the 12Kgm diff is a good option.

Simon

 

That looks like a standard 4Kg's viscous to me - that is some sort of Fuji Heavy batch number [ or whoever made it ] We have similar style numbers on all Viscous centres here in stock.

If it were an upgraded one, then it would have the Prodrive code and so on etched at 180 degrees to the batch number.

David APi

 

David, why would it have a 'Prodrive' code when (japan parts link above) STi market them (and as with a lot of parts are probably Prodrives source), and as they are probably made by Hitachi (who make the Subaru front and rear diffs and at a reasonable guess the stock centres), they will all have Hitachi markings on them, can't see why other than markings they wouldn't look identical as well.

I would imagine that with PD being the authorised STi reseller for the UK 'official UK' parts may have a Prodrive marking.

Simon

 

Dunno. Maybe Prodriive rebuilt them again in the quest for accurate parts. All of the ones I have ever seen are from Prodrive marked suitably. But they are marked 20 Kgs and I am not aware that STi sportparts had a 20 Kgs as an option.

David

 

Did you see the link posted above?

 

Yes I did, But the part numbers don't look like any STi Sports-part numbers that I have ever seen before. They are more usually the original Subaru part number with SA or SP added somewhere as a suffix or prefix. But maybe Japanparts are being cute and have renumbered them for their own purposes. Although the Subaru listed parts below have a right part number shown.

 

OK, can't explain that of course, but its clear they are an STi part, as such almost certainly made by the supplier of the original part to the production lines.

Simon

 

Perhaps I should be looking at a 5mt DCCD unit in order to have the best of both worlds. A quick search in the marketplace is coming up dry.

I appreciate the information learned through reading these forums.

PU., maybe the diffy you have won't be the answer I'm looking for. Thanks for the interest!

Jay Storm

 

I do know how to check if it's a 12 kg diff now. Just need to find the time to do so.

If you change your mind you can always send me an e-mail or pm.

 

Cheers! That would be great!

Jay