border_boxer Posted February 12, 2019 Share Posted February 12, 2019 (edited) Any hiccups with this swap? Is the Forester rear Bias? I'm on 27" AT's and could really use the extra gear. Edited February 12, 2019 by border_boxer Link to comment Share on other sites More sharing options...
matt167 Posted February 12, 2019 Share Posted February 12, 2019 Both are 1:1 center diff so identical.. However if you have a manual it is still 4.11. Auto only is 4.44 Link to comment Share on other sites More sharing options...
border_boxer Posted March 1, 2019 Author Share Posted March 1, 2019 (edited) No modern Subarus are 1:1 nor do they have center diffs? It is 5-spd, bummer on the ratio if that is accurate. Edited March 1, 2019 by border_boxer Link to comment Share on other sites More sharing options...
border_boxer Posted March 1, 2019 Author Share Posted March 1, 2019 I just did a little more research, the 2004 FXT appears to be a 4.44 5-spd. I will have the seller double check the sticker on the diff but I think you are incorrect on this. Link to comment Share on other sites More sharing options...
FerGloyale Posted March 1, 2019 Share Posted March 1, 2019 17 minutes ago, border_boxer said: I just did a little more research, the 2004 FXT appears to be a 4.44 5-spd. I will have the seller double check the sticker on the diff but I think you are incorrect on this. ???? Getting confused. First let's address, when we say the "center diff" ratio we are actually talking about transfer ration Front v. Rear. Not actually the diff but the transfer gear set behind it. There were some models that have "odd" transfer ratios in the trans ...some WRX's....1.1:1 or something.......so those models have 3.7 front diff and 3.54 rear for example You did not ask about FXT ratios, you just said "forester" and NA foresters have 4.11 manuals, and 4.44 automatics. TURBO forester yes will be 4.44 front diff and with 1:1 "transfer" front vs. rear......so rear diff is 4.44 also. JDM options are an unknown too......it's not always clear what they did or didn't get over there. Link to comment Share on other sites More sharing options...
border_boxer Posted March 1, 2019 Author Share Posted March 1, 2019 (edited) I did not mention the FXT part in my post, sorry. Did not have that info when I posted. My understanding is the GD-era LS, OBS are 60/40 F/R torque split. But the fun cars - WRX, RS, FXT - are 40/60 F/R. Basically some trannies can do donuts and some can't Also the horrid understeer which is confused with stability by most of the market. Edited March 1, 2019 by border_boxer Link to comment Share on other sites More sharing options...
FerGloyale Posted March 1, 2019 Share Posted March 1, 2019 2 minutes ago, border_boxer said: I did not mention the FXT part in my post, sorry. Did not have that info when I posted. My understanding is most GD LS, OBS are 60/40 F/R torque split. But the fun cars - WRX, RS, FXT - are 40/60 F/R No. Not for 5 spd manual trans. They are purely mechanical. There is no mechanism for altering the split. It's 50/50 all the time unless one wheel loses traction, then that wheel get's 100% Look up mechanical AWD and how it works. There were a few WRX's like I said with other than 1:1 transfer ratios, and different front/rear diff ratios because of it. But those cars still use a mechanical differential which can only send power to the path of least resistance...there is no way to give front or back "more" power thatn the other.....it's a rotational see-saw.....all about balance of forces on either side of the diff. Link to comment Share on other sites More sharing options...
border_boxer Posted March 1, 2019 Author Share Posted March 1, 2019 (edited) I understand full well how a mechanical differential works. I did not think any thing post-RX used one in the center. My understanding is the center viscous-coupling was essentially a torque converter, moving power around via valves. You are saying that is just in the Auto? My car has a FWD fuse slot, and I have driven it with a broken propshaft. These don't seem like mechanical diff features? Edited March 1, 2019 by border_boxer Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted March 1, 2019 Share Posted March 1, 2019 (edited) the autos have a wet clutch pack and 'bias' is adjustable by the ECU (or tuning I guess) the FWD fuse just turns-off the duty C solenoid so the clutch pack doesn't transfer any power out the back of the trans. Some folks have modified that circuit for manual switching. The system with it's fuse-selection exists primarily to allow use of the 'donut' spare without introducing torque bind. sti's got an adjustable center diff in their MTs. DCCD I think it was called? Edited March 2, 2019 by 1 Lucky Texan Link to comment Share on other sites More sharing options...
border_boxer Posted March 1, 2019 Author Share Posted March 1, 2019 Again, all the data I am skimming through shows the 5MT with a "viscous locking center differntial". If some one can disprove this, please do? Link to comment Share on other sites More sharing options...
border_boxer Posted March 1, 2019 Author Share Posted March 1, 2019 The FWD fuse is kinda the smoking gun in my mind. Could not exist with a mechanical diff. 1 Link to comment Share on other sites More sharing options...
FerGloyale Posted March 1, 2019 Share Posted March 1, 2019 2 hours ago, border_boxer said: The FWD fuse is kinda the smoking gun in my mind. Could not exist with a mechanical diff. it's only on AUTOMATIC trans cars. those use a hydraulic transfer clutch. the have a TCU the manuals have a purely mechanical, non-electronic, differential that is essentially open. 2 hours ago, border_boxer said: Again, all the data I am skimming through shows the 5MT with a "viscous locking center differntial". If some one can disprove this, please do? Bad translation or wishful thinking. The viscous center cannot "lock" it does transfer some force to the non-slipping end when opposite end slips (wheelspin)......but cannot "lock" And if you have a no traction situation for just one wheel, all the force will go there. the viscous unit cannot transfer anywhere near full force when one wheel has no traction, to drive out of a ditch or sunken in snow. It does not "lock" It's also again not electric and there is no FWD mode or fuse or TCU. 1 Link to comment Share on other sites More sharing options...
border_boxer Posted March 2, 2019 Author Share Posted March 2, 2019 (edited) You are getting hung up on the word lock. It's just what the Subie brochure says. Obviously it is not a 4WD system. If the center could lock I would have a switch wired to my dash to make it do so. 1 hour ago, FerGloyale said: it does transfer some force to the non-slipping end when opposite end slips So you agree it is not a traditional mechanical differential. Edited March 2, 2019 by border_boxer Link to comment Share on other sites More sharing options...
border_boxer Posted March 2, 2019 Author Share Posted March 2, 2019 The RX was the last Ru with a non-viscous traditional center diff, anybody want to concur? After doing a little more research, clearly the extra 10% of available torque to rear end comes from one end of the viscous coupling being... more viscous. So to answer my own question, the 4.44 5MT both exists and is rear biased. I guess the FWD drive fuse slot is a dummy in my car? Link to comment Share on other sites More sharing options...
FerGloyale Posted March 2, 2019 Share Posted March 2, 2019 4 hours ago, border_boxer said: You are getting hung up on the word lock. It's just what the Subie brochure says. Obviously it is not a 4WD system. If the center could lock I would have a switch wired to my dash to make it do so. So you agree it is not a traditional mechanical differential. I do not. It is purely mechanical differential and can ONLY ever transfer a 50/50 split. viscous coupler is a mechanical device. I've held them in my hand numerous times, replaced them etc....I know what they are, and what they aren't. And what they are not is a variable torque distrubution device in any conventional sense. they are a LIMITED SLIP, not a locker and not capable of transfering any more or any less power than the balance of traction on the ground allows. The viscous coupler only works to limit some power LOSS, not to add any MORE bias to the front or rear when all 4 wheels are on the ground. When you loose traction it's more like 95/05 % split to whichever wheel gas least. Regardless of front or rear. DOES NOT MATTER THE MODEL if we are talking 5mts with the 1:1 transfer gears. it's "limited slip" abilities are negligable. it's a mechanical open diff and yes the fwd slot on your car is vestigial. 1 Link to comment Share on other sites More sharing options...
FerGloyale Posted March 2, 2019 Share Posted March 2, 2019 58 minutes ago, border_boxer said: .......... rear end comes from one end of the viscous coupling being... more viscous. ME > "FACEPALM" That's not how it works. That's not how any of this works. Link to comment Share on other sites More sharing options...
el_freddo Posted March 2, 2019 Share Posted March 2, 2019 10 hours ago, border_boxer said: No modern Subarus are 1:1 nor do they have center diffs? It is 5-spd, bummer on the ratio if that is accurate. Is this a statement or a question? As stated, all 5mt gearboxes have a mechanical centre diff that has a weak LSD built into it, rated at “5kg”. I’ve heard of a 12 and a 20kg unit too. How they get this weight rating I don’t know. 9 hours ago, border_boxer said: Again, all the data I am skimming through shows the 5MT with a "viscous locking center differntial". If some one can disprove this, please do? When ever you hear/read “plated” or “viscous” with “locking” you know they’re talking about a limited slip differential. There is the DCCD centre diff that’s electronically manipulated through some voodoo stuff that I don’t understand. This device can bind the centre diff to equalise the transfer front to rear and vice versa. 2 hours ago, border_boxer said: The RX was the last Ru with a non-viscous traditional center diff, anybody want to concur? Which RX model are we talking here? There’s more than one and I’m 99% sure they all had a mechanical centre diff with some sort of LSD build in. The L series RX didn’t have a centre diff as it was a PT4WD box, but there are some models that had the dual range AWD mechanical locking centre diff. Rare to say the least. My qestion to you @border_boxer that’s not a statement: Are you after a response to someone that’s swapped from 4.111:1 diff ratio to the 4.44:1 diff ratio? While I haven’t done this exact ratio change, it will all drop in as per factory. You will need to do the usual diff settings in the preload and backlash departments. And possibly look into a different 5th ratio to maintain decent cruise revs. If not you’ll be pulling high revs with the diff ratio swap. Cheers Bennie Link to comment Share on other sites More sharing options...
FerGloyale Posted March 2, 2019 Share Posted March 2, 2019 2 hours ago, el_freddo said: There is the DCCD centre diff that’s electronically manipulated through some voodoo stuff that I don’t understand. This device can bind the centre diff to equalise the transfer front to rear and vice versa. IIRC both the DCCD 6MT AND "VDC" type automatics use a planetary set rather than a spider/pinion differential (or wet clutch pack) Locking/unlocking of the sun gears is how the transfer is changed to be ACTIVELY MORE power to one end vs. the other. these are the only trans Capable of transfering MORE to the rear than the front. Link to comment Share on other sites More sharing options...
el_freddo Posted March 2, 2019 Share Posted March 2, 2019 1 hour ago, FerGloyale said: IIRC both the DCCD 6MT AND "VDC" type automatics use a planetary set rather than a spider/pinion differential (or wet clutch pack) Locking/unlocking of the sun gears is how the transfer is changed to be ACTIVELY MORE power to one end vs. the other. these are the only trans Capable of transfering MORE to the rear than the front. There you go. All I know is they can be the nearest thing to the mechanical lock AWD L series system. There’s a few fellas over here running the dccd in their off-roaders. How long they last is yet to be seen though. That said I guess you don’t run them at 100% duty cycle for lock all the time while offroad - only as you need to. Cheers Bennie 1 Link to comment Share on other sites More sharing options...
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