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Old 02-13-2018, 04:01 PM   #26
mrsaturn7085
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Center diff. changes are as follows:

2000-2005 - Early Style
2006-2007 - Late Style, Oil Pump Drive Gear - 38913AA190
2008-2017 - Late Style, Spacer (no oil pump) - 38913AA210
2018 - new mystery part number (and I would love to crack one of these open)

38913AA210 was installed on *some* 2008 models to deplete remaining parts. In this application, the oil pump drive gear just sat there spinning all by it's lonesome self. Otherwise, the 190 and 210 parts are identical.

Hopefully someone can upload some images of the 2018 model diff. soon! Unfortunately, pictures of the 2006-2017 diff. aren't even easy to find online... so we shall see!

Knowing Subaru, the original post stating Subaru gutted a performance part and marketed it as a benefit is probably true. Generally, the FSM or dealership tech. notices will have some cross-sectional views of the diff. - maybe someone on the inside (or with $300-400 lying around) can source the dealer documents or FSM soon!
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Last edited by mrsaturn7085; 02-13-2018 at 04:14 PM.
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Old 02-13-2018, 04:47 PM   #27
jamal
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Aside from the oil pump there are some differences between the sti center diffs.

The 35:65 spilt in 04-05 compared to 41:59 in later cars is the most well known one.

But the 06+ diff added a "torque cam" to the center diff. What this does is acts kind of like a clutched lsd, where a speed difference pushes the cams out and brings the clutch plates closer together. However, this mechanical system can not force them all the way closed like the electromagnetic clutch does and it only operates in the "0-30%" lockup range.

So basically what it does is let the electromagnetic system not do anything until more than 30% lockup is needed. Maybe the cammed mechanical operation works smoother at low speed differences and input torques like in a parking lot or whatever where the previous dccd would start giving lockup when it's mostly not needed.

It sounds like maybe they got rid of that for the 2018. Makes the diff simpler to make and cheaper and they've probably improved the control strategy a bit too.

I could also see the only 30% lock causing wear issues if you manually set the diff to the lower/open settings a lot in slippery conditions. Like going and doing donuts in the snow with the diff open would have those plates slipping against each other.


I have not ever seen any numbers quoted for the torque capacity of the diff when fully locked but I would guess it's a good portion of what the engine can do if not more. So at full lock it is mechanically about the same as a 4wd truck.

Last edited by jamal; 02-13-2018 at 07:07 PM.
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Old 02-13-2018, 05:06 PM   #28
mrsaturn7085
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Quote:
Originally Posted by jamal View Post
Aside from the oil pump there are some differences between the sti center diffs.
Yes, this is correct - I abridged the pre-2006 notes above but the largest change took place between 2005 and 2006. The entire design changed from a diff. that could turn fully open (pre-2006) to one that always had a passive mechanical stage (2006+).

FWIW - if anyone wants to have a 2018 diff. disassembled, photographed, and reassembled, I've got the oddball snap ring tools to do it (for science!). Preferably local - but I'm happy to pay return shipping to document this.
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Old 02-14-2018, 04:35 PM   #29
Sparc
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I still haven't found a wrecked 18 yet for a reasonable price to disassemble and swap if there is any actual benefit. I would love for someone else to foot that bill... I'm certainly not going to pay 2.6k for a new one.
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Old 02-26-2018, 06:59 PM   #30
04stigeorge
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Quote:
Originally Posted by mrsaturn7085 View Post
Center diff. changes are as follows:

2000-2005 - Early Style
2006-2007 - Late Style, Oil Pump Drive Gear - 38913AA190
2008-2017 - Late Style, Spacer (no oil pump) - 38913AA210
2018 - new mystery part number (and I would love to crack one of these open)

38913AA210 was installed on *some* 2008 models to deplete remaining parts. In this application, the oil pump drive gear just sat there spinning all by it's lonesome self. Otherwise, the 190 and 210 parts are identical.

Hopefully someone can upload some images of the 2018 model diff. soon! Unfortunately, pictures of the 2006-2017 diff. aren't even easy to find online... so we shall see!

Knowing Subaru, the original post stating Subaru gutted a performance part and marketed it as a benefit is probably true. Generally, the FSM or dealership tech. notices will have some cross-sectional views of the diff. - maybe someone on the inside (or with $300-400 lying around) can source the dealer documents or FSM soon!


Honestly it's almost identical to the 2017.
Your not missing anything.
Took me a bit to see a difference but nothing to write home about.
So the dccd Center diff 38913aa210 part number
Stops after 2017
Becomes 38913aa260
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Old 02-26-2018, 07:07 PM   #31
04stigeorge
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Quote:
Originally Posted by 04stigeorge View Post
Honestly it's almost identical to the 2017.
Your not missing anything.
Took me a bit to see a difference but nothing to write home about.
So the dccd Center diff 38913aa210 part number
Stops after 2017
Becomes 38913aa260


First pic is bottom of 210 07-17
Next is the 2018 260
Only difference...
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Old 02-26-2018, 07:26 PM   #32
carnz-pj-410
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Heres an excerpt from the 2018 STi "New Car Info" FSM about the DCCD.

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Old 02-26-2018, 08:10 PM   #33
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Thanks!

So, basically back to the 04-05 diff.
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Old 02-27-2018, 04:36 AM   #34
mrsaturn7085
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Quote:
Originally Posted by jamal View Post
Thanks!

So, basically back to the 04-05 diff.
No. It's still 41:59... but good lord - they took the ramps out but left the entire plate/disc assembly intact. The only reason I can fathom they did this is to prevent warranty claims on center diff. wear.

This change will negatively impact late corner and corner exit traction. As expected, they're trying to sell a cost-cutting measure as a benefit. There's a lot of moving parts to juggle here... but I *think* this will make the car feel more like a RWD car on the corner exit.
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Old 02-28-2018, 01:01 PM   #35
jamal
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If you generate x amount of lockup does it really matter if the plates are being pushed together by a cam or not? more throttle and less steering = more lockup, so at corner exit dccd is probably already well over what the mechanical part can do.

But maybe braking on loose surfaces the mechanical bit would add some stability since that is when the electronic diff is mostly open.

But now when I think about what's happening in an 06-17 when you get a lot of wheel spin with the diff all the way open (hey it's snowing- lets do some drifts and donuts!) I kind of cringe.
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Old 02-28-2018, 02:27 PM   #36
mrsaturn7085
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2006-2017 DCCD Enhancements

Start at page 14 and then ask yourself why Subaru took the time to write 8 pages explaining why the mechanical diff. stage improved the DCCD in 2006 and then a single quick note in 2018 FSM telling you the mechanical stage was abolished "to improve turning performance in turning acceleration".

Here's another possibility - in the FSM 'turning performance' = less customers complaining about low-speed center diff. binding (which is more often than not, regular stick-slip phenomena and not an actual problem).
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Old 06-22-2018, 02:34 PM   #37
linkubus06
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Any updates on this? Have people actually felt the difference with the new gutted DCCD?
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Old 06-22-2018, 03:02 PM   #38
mrsaturn7085
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The difference you feel will entirely be in parking lot U-turns. There is a silver lining to this change - Subaru left the mechanical diff. intact so you can swap the ramp sections and re-activate it...

The downside? You can't buy the guts of the DCCD separately. My gut feeling says that STI will offer these parts in the near future through their competition parts dealers (much like they've offered TGV deletes, diff. rebuild kits, etc. in the past).
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