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Rear LSD for 2.0D

('09-'13) 
16K views 36 replies 9 participants last post by  delta5150 
#1 ·
Hello everyone,

I'm about to make a final decision on purchasing a new Forester, however I am lingering, because of three items. I searched this forum and found some answers, but not all. Hope you can help (esp. with the first one):

a. Do you know whether Cusco LSD fits into the rear of 2012 2.0D 6MT Forester? The manufacturer seems not to be sure, as gasoline Foresters are more popular in Japan. If not, maybe Kaaz?

b. From reading various posts, I understood that "DSC off" button doesn't completely turn off traction control and interferes with sideways fun. It seems, that there is a an option to remove one fuse, which deactivates ABS, together with interfering electronics.

c. I read some posts indicating that there are pretty straightforward ways to tune the 2.0D from 147AG to 170AG. That would be nice.

Insight is appreciated a lot.

Thank you!
Oxy-
 
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#2 ·
Well since the Diesel Forester's aren't available here in North America, I don't know specifics on how they are equipped from the factory.

I would suspect that they come with a factory R160 LSD setup similar to the XT Foresters. If this is in fact true then any R160 aftermarket LSD should work on them. If the diff casing is different then a WRX case would suffice with your ring and pinion gears swapped over and fitted along with the upgraded LSD.

Best of luck.
 
#5 ·
Yes, 09-13 model has no LSD in front or rear.

What I found so far is:

http://www.cusco.co.jp/pdf/P205-209.pdf

For the 2012 Forester and 1.5way LSD, it seems, this fits:

SH5 (07.12 〜)EJ20T
Front: LSD 180 C15
Rear: LSD 183 L15

Incidentally, I received the following reply from a tuning company:

Most Forester?legacy models seem to be DBF2015 when open diff<...>
For Cusco it's model LSD183 Viscous/Open
Which corresponds to what the Cusco catalog is telling.

It seems, it all boils down how to double check whether stock diff is DBF2015.
 
#11 ·
Yeah but at what rpm is it reaching 450nm? my diesel has 350nm from 1400rpm that means there is alot of load put on the diff to work hard when it under max load already just trying to accelerate.

Subaru are very concerned about the torque load and stress put on their drive line, this is why they didn't bother with a 5 speed manual also why they fit temperature monitoring to the rear diff which isn't even lsd at all. From what i'm told only STI's and diesels have this setup. the issue isn't total torque it's that as soon as you start letting up the clutch it having to cop 300 odd nm.
 
#12 ·
Which is odd since the 6MT they threw in the diesel is a re-geared version of the new Outback and Legacy/Liberty split-case 6MT based off the 5MT.

My peak torque isn't until 3000RPM.
for how cheap you can pick up a used FXT VLSD, why not try it and see if it pops. Then you still have the old rear diff to switch back to instead of possibly breaking your stock diff with the installed LSD.
 
#15 ·
for how cheap you can pick up a used FXT VLSD, why not try it and see if it pops. Then you still have the old rear diff to switch back to instead of possibly breaking your stock diff with the installed LSD.
I know that Kaaz, and am pretty sure that Cusco too, LSD is a full differential. It's not like Phantom Grip "add-on".

You open up the diff case, remove the stock diff, remove the ring gear, put the ring gear on the new one and put inside the whole clutch-plate LSD diff. You are left with the stock diff (without the ring gear) on your shelf.

Moreover, as these diffs are designed for racing, I'm sure they can cope with more load than the stock one. I have installed Kaaz on my other car a few years back. It's the best LSD I had. Viscous LSD is like open diff compared to clutch-plate's locking performance.
 
#13 ·
Mate that is great news, so the diesel 6speed is no stronger then the 5speed? do you have any doco for this? I really want to swap to the 5speed as there is a company in here that make custoom gearsets for them better suited to offroading but they insist my diesels torque surge will destroy the 5speed.
 
#21 ·
Mate that is great news, so the diesel 6speed is no stronger then the 5speed? do you have any doco for this? I really want to swap to the 5speed as there is a company in here that make custom gearsets for them better suited to off-roading but they insist my diesels torque surge will destroy the 5speed.
It is merely a belief at this point in time since nobody has had the balls to push the envelope with the smaller 6MT. The STi gearbox uses an 85mm internal shaft spacing while the split-case 6MT and 5MT have a 75mm shaft spacing.
My understanding is that they narrowed the gears on the 6MT to squeeze a sixth gear in a similarly sized transmission case. The 75mm transmissions are known for their case flex partially due to the split-case design, but compared to the larger 85mm 6MT the 75mm units aren't considered strong.

There are also some companies that are making blast plates for the 5MT which help to drastically reduce the amount of case flex. From what I've seen though the new case with the 75mm 6MT has a lot more structural reinforcement to prevent flex compared to the 5MT.
 
#18 ·
So there is alot of torque managment in first gear. is this able to be tuned out? i find the foz very easy to stall in first gear off road. in fact it can be damn annoying as i'm sure the amount of stalling the can happen in some situations i've been in, i'm sure leads to more clutch wear then might be saved by them limiting the torque.
 
#19 ·
Subaru have been fine-tuning the off-idle response of the diesel since it's introduction. Trust me, they were much easier to stall when first introduced, my own Forester has had three or four software updates and they've all felt slightly different at the clutch biting point.

Problem is you've got conflicting requirements- driver need, DPF loading, DMF longevity. Increasing fuel before the turbo spools makes soot which the DPF then has to deal with. Torque at too-low rpms overloads the DMF, bouncing it off it's endstops and reducing it's life. It's a fine balance and the "best" solution is slipping the clutch at slightly higher revs. But sadly the diesel's clutch is rather grippy and doesn't like that...
 
#20 ·
Well i don't know about the older ones but ours is very good on road never really stalls even in traffic it deals very well with just letting the clutch up with no throttle and just creeps forward slowly even on slight inclines. but offroad on steep hills or on losse road or dirt, or when it has to drive up over something it just stalls so easily. turning off traction controll helps a bit but yeah end up having to really work the clutch.

I'd really love to be able to convert the traction control button to a switch as when it stalls it doesn't come back on.
 
#23 · (Edited)
^interesting... it appears the diesel 6MT has less bracing than the Legacy/Liberty Turbo 6MT.


Here is the Legacy's 75mm split-case 6MT:



Compared to the diesel 6MT you referenced:



Here is the split-case 5MT for comparison:




*NOTE*
The obvious difference that I can see is that they have also gone to a sealed cable-type shifter arrangement compared to the older rod system. This new system won't feel as direct as the old system, but will have fewer seals to maintain.
Also the Legacy/Liberty gearbox doesn't have the downpipe clearance of the other two setups. Ignore the extra cable on the farside of the 5MT photo, that is the VSS cable which doesn't exist on the new transmissions.
 
#24 ·
Back to LSD... Maybe someone has clutch-plate LSD installed in the rear of 6MT or 5MT 3rd gen Forester?

After you have a fully locking LSD installed, is center viscous differential strong enough to direct power to the now-demanding rear? If it were not strong enough, it would just turn front axle and no power to the now-two-power-asking wheels in the rear...
 
#25 ·
i've called a few places here, seems no one has done an LSD in the rear of an SH yet. I've been thinking of buying a cheap second hand SG FOZ auto diff as they are 4.44 ratio and just bolting that in with the VLSD.

Reports on offroadsubaru is these do perform ok in mud snow and sand. they don't help with one wheel in the air situations but for the price they can be had and the install is much more diy.

Just need to see if my tail shaft CVs etc will mate up.
 
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