AWD lockable vs AWD viscous gearboxes .

discopotato03 · Post by **discopotato03** » Thu Apr 03, 2008 6:46 pm

Hi all , I think I know the answers but this much I know from people I trust .

I am at a fork in the road and can go either way , the pros and cons are as follows . BTW my box is EA/DR/FT but yet to be used .

The L type AWD box is good for an RX because it fits straight in with virtually all the std bits ie linkages tailshaft etc and has the std diff and gear ratios .
Mine will be getting the 92 Lib DR closer 1-4 ratios but keeping the std 5th for highway use .
The drama is that the open centre diff is good to a point but can lose all the drive at either end in some circumstances . The rally people tell me that with AWD Turbo Lasers (plate rear LSD/open center/open front diffs) traction is reasonable except for uphill hair pin bends in very wet slippery conditions where they spin the fronts only and can't steer . Locking the center diff is a big help except when on hard surfaces .
Stuart Wilkins rallied an RX in the late 80's and he mentioned that the very last of the RX's had a viscous center diff like an EJ AWD car but in the short L FT style box . Never heard of that one . I think he prefers the viscous center diff type and I don't know which way to go .

The little voice is telling me to stay with the locking box and close ratio gear set because if all else fails I can lock the diff .

The pluses on the viscous box is that parts are more readily available read easier to find if they break anything . Also depending on which rate of viscous hub you use in theory it will always drive both ends to varying degrees torque split wise . Also pinions are mostly available unlike the unique L AWD ones .

If any ones had experience with both types of gearbox in an RX Turbo can you lets us know the pros and cons from you point of view .

Cheers A .

vincentvega · Post by **vincentvega** » Thu Apr 03, 2008 6:49 pm

you have never really said what you want this thing for. is it a road car or a rally car?

discopotato03 · Post by **discopotato03** » Thu Apr 03, 2008 9:35 pm

Road mostly , plus the odd explore of service vehicle tracks .

A .

Matatak · Post by **Matatak** » Thu Apr 03, 2008 9:40 pm

i say viscous. especialyl when its going to be driven on road more.

Ben · Post by **Ben** » Thu Apr 03, 2008 11:32 pm

I've had a L series constant box in a mildly worked RX (exhaust IC, 11psi Boost) and it didn't even take a hairpin to get the inside front to let rip. Any mild uphill especially corner that had a bit of camber to it would see the tyre on the inside breaking loose.

I was also able to lock the handbrake on hard, dump the clutch and get smoke from both back tyres.

For onroad go the STi 20kgm centre, for offroad go the lockable, but only if you don't already have part time box as that is sooo much easier and cheaper.

I think there was some talk a few years back (when I was playing with these things 8 years ago now) that the Liberty viscous housing would work on the EA box. Or the EJ internals and centre diff housing on the FWD EA box or something like that - can't recall fully.

Gannon · Post by **Gannon** » Fri Apr 04, 2008 5:29 am

Yeah there was a thread not all that long ago about it
EJ AWD into EA 4wd gearbox

discopotato03 · Post by **discopotato03** » Fri Apr 04, 2008 8:01 am

Its hard to know which way to jump because both options have advantages and disadvantages .

I don't want to lose the 3.7 diff ratio and I don't think there is one for the EJ type gearbox .
I also don't want wheelspin issues and I don't know if a Torson or clutch front LSD will stop it with an open center diff . Tyres would make a difference and are at least easy to change .

If what has been suggested is true there must be 4 different grade viscous centre diffs ie 4/8/12/20 for Lib/WRX and two competition/STi types .

Thoughts , cheers A .

vincentvega · Post by **vincentvega** » Fri Apr 04, 2008 8:47 am

Gen2 dual range boxes are 3.7

discopotato03 · Post by **discopotato03** » Fri Apr 04, 2008 3:30 pm

Yeah ? Thats good news . What gear ratios do they have .

I'd say those would not be a cheap thing to buy .

Thanks for the tip , cheers A .

Phizinza · Post by **Phizinza** » Fri Apr 04, 2008 6:01 pm

FT4WD open centre diff is bad:
Dirt roads,
rallying.
Good:
Onroad,
Offroad 4x4.

AWD EJ is good for:
Onroad, better then FT.
Sand, not quite as good as as FT lock.
Rallying.
Bad for:
Offroad 4x4.

Pretty obvious, yes. But you should be able to make up your mind on what you want just by thinking what you want your car for and this list.

PeeJay · Post by **PeeJay** » Fri Apr 04, 2008 8:43 pm

My opinion is the L AWD box is useless compared to my new 2004 Forester one. With one front wheel in the air I can still easily spin the rear as well despite only having the standard viscus centre. Even driving up the side of a mountain I still can't get the thing to loose grip.

But then again the 2nd time I actually locked the centre on the L AWD I got it jammed in first and broke 2nd, 3 kms from the main road, 30 kms from the nearest town, and during a snow storm in the late afternoon... Not a fun day.

discopotato03 · Post by **discopotato03** » Fri Apr 04, 2008 9:23 pm

Damn Subaru , if they'd made the viscous version with a lock it would have solved 95% of the issues . No wonder Mitsy went from the viscous to the active hydraulic in the later Evolution Lancers .

Out of curiosity has anyone used higher rated viscous center diffs than the (I think) 4Kg rated Liberty one ? I have some feedback on what the 20 Kg rated STi one is like and its a bit over the top by the sounds of things . Possibly the 8 or the 12 would be a little less harsh when driven sedately .

BTW Stuart Wilkins mentioned that the very last of the L AWD type may have had a viscous center diff - as inside the L AWD type extension housing . Anyone know anything about this or if there is a viscous centre around for the short extension box ?

Also LR/HR detent aside are there any issues with linking up the selector rod to the selector handle ?

Cheers A .

Gannon · Post by **Gannon** » Sat Apr 05, 2008 6:52 am

How much power are you expecting out of your EA82T? If you are gonna be running stock boost, you are looking at 120hp, maybe 130 with a few mods if you are lucky. Id just go with the FT4WD with the open diff.

If you are planning on pushing 10psi or more, go the EA82 5 speed with a liberty rear transfer housing to give you the VLSD.

Why do you wanna change your gear ratios?

YouTube · Post by **El_Freddo** » Sat Apr 05, 2008 7:01 am

Suparoo wrote:Why do you wanna change your gear ratios?

From what I've read Adrian's after an everyday car that's a bit of fun, handles well, a little unique yet still gets the best performance out of the old '82 turbo. And a car that's capable of an odd day on the track.

I'd love to see what he's done to ellie, it may be a lot of money but everyone's different and have their reasons.

As suparoo has mentioned you can use the vicsious centre on the EA housing with EJ rear extension. I dunno if you'll need to fab a crossmember but the linkages will need to be changed as will the length of the tail shaft.

Cheers

Bennie

discopotato03 · Post by **discopotato03** » Sat Apr 05, 2008 7:02 pm

Suparoo I don't know what it will ultimately make but I do know that it with breathe better with modified heads and a bit of fettling in its spider inlet manifold . The static CR will be 8.6 instead of 7.5 and the header designed to vent the engine and power the turbo - not just be an over sized EGR pipe .
ATM the flywheel is being lightened because they weigh a tonne , far too much for a short stroke 1800 .
The aim is to have a broad spread of torque and be hopefully free revving for the dinosaur water cooled dak dak that they are .

A close ratio gearbox is always better than a wide ratio one for any performance application . It allows you to keep the engine revs in a narrower band wherever in the engines rev range you like . For example if you drive around at lowish revs using low down torque changing up/down often you can get good fuel economy and sedate manners .
If you want it to stay around its torque peak that's easy to .
If your going balls to the wall you don't need to go right up into the red because the revs don't fall as much after the up change .
Also close ratio gearboxes are much easier on their baulk (syncro) rings because the speed difference between adjacent gears is less so they don't have to brake or accelerate the next gear as much . By this I mean drag the idling gear up to or down to the same speed as the coupling sleeve to synchronize their speeds and make a smooth quiet engagement .

All wide ratio gear sets do is widen the total spread between the lowest and highest ratio ie 1st and 5th . I'd say Subaru did this to the RX Turbos because they knew they would develop more torque than the Carb or N/A version and so would pull these wider spaced ratios without too much fuss .
I'm keeping the 3.7 diffs (no choice with L AWD) because with larger diameter wheels the total gearing goes up . What subie did was make the upper ratios shorter in the close box so with the wheel size increase what I hope to achieve is same top gearing with taller 1-4 , just skinning the cat from the other end .
Anyway because its possible to run the engine in a narrower rev range its possible to keep it closer to its torque peak and traction will be more of an issue .

Because I'm probably an incurable petrol head , toned down on what i used to be , I like cars to have a bit of flare and the lure of the giant killer is too much to resist . Back in the Mini days this was called the wolf in sheeps clothing thing and can be very entertaining - provided you don't go silly on public roads .

I think this little white lightweight lamb chop should be a quick way to get around Sydney's crowded burbs without attracting undue attention from unsuspecting victims or the constabulary .

If I get out of it all for around 10G its less than half the price of an Evo 6 and I've learnt so much along the way . The 6's will fall in price and get more affordable as the 7/8/9/10 gain popularity . By then I can just buy one and have most of the goodies out of the box .

One of these days I'll own a std factory car , maybe ? Dunno .

Anyhow the final decision is to run this L locking box in close ratio form and see what happens .
The better suspension is on the way and if I can get around Subarus @#%&* tendency to stand up on its front wheels like bloody praying mantis under acceleration I may just get the front to stay down a bite a bit better . To do this means altering the height of the radius rods to give it more front anti climb geometry . The less anti dive by product won't be an issue when it gets higher rate front springs .
Gee tells me this L AWD box is the best one his gearbox expert has ever opened up and quite tight (tolerance wise) for its age . That fellas gonna laugh when he opens it up for the 4th time but he knows them well and runs one himself . Its had EA and EJ SR casings on it , then back to EA and converted to DR for me and now another gear set to go in .
If there is ever a next time it would be for the alternate extension and an early WRX 8 kg viscous center diff change - but only if I can't get this car to work suspension and tyre wise around the L AWD open center diff characteristics .

Cheers A .

BlackMale · Post by **BlackMale** » Sun Apr 06, 2008 11:02 pm

A, its sounds like its all going well and i have been/will continue to follow with interest. You said

discopotato03 wrote: I'm keeping the 3.7 diffs (no choice with L AWD)

Just be aware that they were also released in a 3.9 L AWD (i have 1). This will prob not help you at all however technically there is another L series AWD option.

AndrewT · Post by **AndrewT** » Mon Apr 07, 2008 12:57 am

Hey Jaffa can you post up the gearbox identification number on that gearbox? It's near the starter motor.

discopotato03 · Post by **discopotato03** » Mon Apr 07, 2008 8:59 am

Hi BlackMale , yes the 3.9 was std on the Vortex XT6 and they are a pretty rare imported bird in Australia . By no choice I mean finding the L AWD 3.9 pinion (and its matching crown wheel) would be very difficult .
I'm not really fussed about the 3.7 FDR and would actually prefer one a little taller ie 3.5 or 3.6 . With the shorter close ratio gear set this would bring the overall 5th ratio up to std for an RX if not a little higher . If 1st was a little high at times then the taller turbo low range has that covered . If you multiply 3.7 by 1.192 you end up with an effective 4.41 final drive ratio . The overall 1st low is 15.6 to 1 .

What some people do is have the pinion gear removed from the L AWD's unique shaft (these are the longest of all the 5MT box pinion shafts) and have a 3.9/4.1/4.4 one welded (properly) in place and use its matching crown wheel so any option is available if you have an L AWD box to start with . I believe the pinion mod costs ~ $400 .

BTW what's the 3rd option ?

Cheers A .

bluesteel · Post by **bluesteel** » Mon Apr 07, 2008 9:52 am

hey discopotato,
do you know anyone who hase done the pinion swap on and what sort of success they had?
also do you know where it was done?

discopotato03 · Post by **discopotato03** » Mon Apr 07, 2008 11:24 am

Not personally but Gee does . From him the story is that the gear mob doing that mod reckon other things in these boxes would fail before their front pinion would .

When I mean cut and weld the items need to be softened (can't machine or cut hardened steel without destroying the component) and then machined (both gear and shaft) so they mate together accurately . I don't know which welding processes they use but Gee said the finished pinion is re hardened and X rayed to check for any faults in the process .

From memory the fellow doing my gearbox has a locking box in a brumby (or an L ?) and his is either 4.1 or 4.4 .

Cheers A .