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Discussion Starter #1
Ok so I have seen two '13 Outbacks, both 2.5 models, one looked to be a white premium and the other was the cool BBP with SAP model. Anyway I know it's crazy I notice minor details like this when I see other Outbacks but when did they change the rear differential housing to a " finned " casing?

The one on my '11, 2.5i CVT is smooth aluminum looking. The two cars I've seen had little fins or ribs for additional cooling? Useually this is seen on higher end performance cars fitted with a limited slip differential to aid in cooling the fluid.

Example, my '13 WRX has the smooth diff housing like my Outback, understandable as both are open differentials. However the finned unit that I've seen so far on the '13 Outbacks looks like the same finned diff housing on the WRX- STi model??

Does anyone know when they switched? or what exact models of Outback get this differential? I've seen '13 Outbacks with the smooth one too like my '11 Outback so it appears there is no rhyme or reason for it, but I'm sure there is. Purhaps manual Outbacks get it? But I didn't think you could get manual and BBP/SAP either? I thought you could only spec a manual trans up to a premium model so who knows. Not a big deal just a curious car/ techy nerd wanting to know exactly.
 

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My neighbor has a '13 2.5i Limited and the rear diff housing is finned.
My '12 is smooth.
 

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2013 OB 3.6R SAP
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Yes, my '13 3.6r has the cooling fins.

Looks like Subaru decided that the rear diff needed a bit more cooling.
 

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Discussion Starter #5
Ok weird. So I was just behind a brand new '13, what looked to be a premium and it had the smooth diff housing. Then saw a white 3.6R probably '10-'12 and had the finned. Neighbor a few houses down has a white '13 in the driveway, has single tailpipe but has the finned diff, here's something even more strange is that it's a 2.5i with no pzev badge. All 2.5i's in California are pzev so that's why it's weird.

Are manual 2.5's pzev? or just CVT? Ohh BTW in my town Outbacks are so common I see one about ever 60 seconds, it's the new Camry/Accord around here lol. Anyway I'm over due for servicing on my car so I will go to the dealer and poke around and see what's- what with this differential tomorrow. Will report what I find out.
 

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2011 Outback limited 3.6
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The finned housings are for strength, makes the rear end housing stronger! At least thats what we do in the hot rod world. some do it just for aesthetics.
 

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Discussion Starter #7
The finned housings are for strength, makes the rear end housing stronger! At least thats what we do in the hot rod world. some do it just for aesthetics.
Yeah we know what it's for, just wondering why some Outbacks have it, and why some don't. It's not like there is a 400hp beast under the hood of this car.
 

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2018 Outback Limited 2.5i Dark Blue Pearl/Ivory w'Eyesight
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Ok weird. So I was just behind a brand new '13, what looked to be a premium and it had the smooth diff housing. Then saw a white 3.6R probably '10-'12 and had the finned. Neighbor a few houses down has a white '13 in the driveway, has single tailpipe but has the finned diff, here's something even more strange is that it's a 2.5i with no pzev badge. All 2.5i's in California are pzev so that's why it's weird.

Are manual 2.5's pzev? or just CVT? Ohh BTW in my town Outbacks are so common I see one about ever 60 seconds, it's the new Camry/Accord around here lol. Anyway I'm over due for servicing on my car so I will go to the dealer and poke around and see what's- what with this differential tomorrow. Will report what I find out.
Two possibities for "non" pzev gen 4's in CA. First, someone took the PZEV tag off. Second, and more likely, the OB came from out of state. With used vehicles, transporting between states is common. Many of the former rental cars offered for sale in CA are from out of state. The current state of emission controls makes it somewhat easier to move cars from states other than CA into CA.
 

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2012 Legacy 2.5GT-L
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So how "finned" are the rear diff covers? There are a bunch of different versions - it looks like the T-type rear differentials (for 2012, the 6MT or the CVT in the outback) should be smooth, but the VA1 or VA2 type (in 2012, the CVT in the Legacy is VA1 and the 5AT is the VA2 (in 2013, the Outback CVT has the VA1 as well) - both are sort of finned (the VA1 has the drain/fill plugs on the rear cover, but the VA2 has them on the side of the rear diff housing) - the VA1 has vertical fins, and the VA2 has vertical and a couple of horizontal ones (sort of like a grid))
 

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2018 Outback Limited 2.5i Dark Blue Pearl/Ivory w'Eyesight
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My '11 3.6 has vertical fins
 

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My 11 2.5i CVT has a smooth one IIRC. It's likely just a product of different suppliers, as I can't see why else this range of years has both.
 

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Discussion Starter #13
I'm driving a middle of the road 2013 2.5i, Pzev, CVT service loaner while I'm getting the 30K done on my '11 Outback. Here is the new differential housing I'm talking about. It actually looks like the ribs are for strength and not necessarily cooling as they arn't deep fins like on performance cars. Weird I just wonder if Subaru did this becuase there was a problem with the early design breaking? or did they do it for added off-road protection. The latter is odd as the butt-end of the casing is relatively protected from rocks and such while the underside is still smooth & flat??

 

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2019 Forester Sport. Love the Orange.
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.... Weird I just wonder if Subaru did this becuase there was a problem with the early design breaking? or did they do it for added off-road protection. The latter is odd as the butt-end of the casing is relatively protected from rocks and such while the underside is still smooth & flat??

And they can't back up over a curb to run into anything anyway......:rolleyes::rolleyes::rolleyes:
 

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2016 Carbide Gray Limited with Moonroof, Nav, and Eyesight
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Perhaps a weight saving design, thinner with ribs? I also agree with a different supplier making a slightly different design that meets specs.
 

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I'm driving a middle of the road 2013 2.5i, Pzev, CVT service loaner while I'm getting the 30K done on my '11 Outback. Here is the new differential housing I'm talking about. It actually looks like the ribs are for strength and not necessarily cooling as they arn't deep fins like on performance cars. Weird I just wonder if Subaru did this becuase there was a problem with the early design breaking? or did they do it for added off-road protection. The latter is odd as the butt-end of the casing is relatively protected from rocks and such while the underside is still smooth & flat??

The differential cover isn't likely to provide any protection. If you want protection, do what I did and install the Primitive skid plate package. I went with triple protection (engine, CVT, rear differential) for $390 and I'm confident it will protect against darn near anything! :29:

LEGACY
 

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2013 OB 3.6R SAP
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Yes, the cover on my '13 3.6 is different than the one shown above - mine has deeper fins/ribs in a both horizontal and vertical pattern. The cover design on my car seems more believable as cooling fins than the pic shown above, but yes, could be for strength as well. I suppose the greater torque output of the 3.6 could demand both.
 

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2012 Legacy 2.5GT-L
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As I mentioned above, for the 6MT and 2012 CVT in the Outback, it has the T-type rear differential, which is smooth.

For the 2012+2013 Legacy CVT, and the 2013 Outback CVT, it has the VA1 rear differential, which has vertical fins.

For the 2012+2013 Legacy and Outback with the 5AT, it has the VA2 rear differential which has vertical and horizontal fins.

 

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2013 OB 3.6R SAP
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Thanks for making that clear.

Do you know the difference between these differentials? I did some quick searching and found some comments on the Legacy forum that the VA1 is a limited slip diff, as is the VA2 but a little more sophisticated than the VA1. Not sure if that's true given the comments on this board that all recent OBs have open rear diffs.
 

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The type seems to refer to the housing, then there are specific identifiers - none of the USDM 10+ Legacy/Outback rear differentials are limited slip. Here's the chart for 2012:


And here it is for 2013:
 
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