Is it AWD?

[discopotato03]

From an L Series convert , yep these boxes are good things because FrWD is pretty hopeless . Its quite rare for my RX L to spin wheels and if it does its over roads where a water run is diagonally under the car and it gets a very slight slip of one front wheel . Mind you my car has large anti roll bars which to a degree resist wheel travel . The rest of the time open center diff AWD is brilliant . I think the only reason the lock was provided is because if you lifted a front wheel all the drive would go to it and you go nowhere . Oh and to give positive 4WD BTW .

AWD does zip for handling in a std early Subaru , driving all four still lets you understeer into the scrub when the caster and camber are as standard .
To be good you'll need power steer neutral camber and if possible less negative caster - positive caster preferably .
Probably modified control arms and properly made caster/radius rods which will increase the front track and luckily L Series front shafts are a bit longer .

The bits most often damaged or missing from those early AWD boxes are the rear exhaust hanger and the steady mounting bracket and arm .
Also the pitch stopper and the box end bracket can be hard to get .

Make sure when you fit it some kluts hasen't left a broken off bit of the speedo cable in the box , in an L undo the vacuum can gadget off the box so you can get it up in the tunnel .

These boxes should have been an option on ADM L's but in that era it was hard to impress upon people the advantages of AWD road cars . They'd rock up to a car yard on a fine sunny day and try both round the block . They'd come back claiming they couldn't tell the difference and certainly didn't want to pay any more for it .
To be honest most cars that had the option didn't already have the extra diff and shafts in the 2wd version so the price difference was significant .

If Ls were new today and AWD was a $300 option you'd jump at it wouldn't you .

A .

[El_Freddo]

cant ya tell by the 4wd selector?

ie youd only have the two notches when shifting it by hand, awd hi range and awd low range?

part time box should have three notches? fwd/4wd hi/4wd low?

just guessing but

In the 4wd selector lever this is true. The AWD dual range gearbox only has a lever near the bell housing for the high/low range selection, there is no rod that passes THROUGH the rear of the gearbox under that flat plate.

To identify an AWD dual range L series gearbox: On the driver's side of the gearbox on the rear casing there will be a lever for the centre diff lock. IF its a true awd L box the pivot for this lever will be near the middle of the rear case. If it pivots at the bottom of the rear casing its a part time single range gearbox. You can also remove the top plate (the flat one held by 4 bolts) to reveal either a centre diff (wet pants time) OR a mechanism that engages the rear end for the single range gearbox. Both use the vacuum actuation diaphragm.

Unfortunately I don't have any pics handy for this gearbox and the shed its stored in is some time away from me at the moment

yeh that's what I meant, just pointing out that it's just a normal open-diff in the middle, which isn't quite the same as what most people know as "AWD" - ie, a VLSD centre as per Libs, WRX's etc.

Yeah... ah, I don't agree with this statement - it is AWD until you really start to push the box and somehow induce wheel spin on the front end, this is where the only difference is between an L awd and an EJ awd gearbox for on-road use. As stated the EJ has the centre LSD to put power to the rear in the event of front wheel spin - if you by chance get rear wheel spin it will continue to spin as the centre LSD only operates in passing power/torque to the rear wheels when there's a loss of traction.

Best of luck dave, I hope for you that its an AWD gearbox for the L - should've put that in Hatchie (and KEPT IT! Or at least sent it over here for "storage").

Cheers

Bennie

[sublime]

AWD does zip for handling in a std early Subaru , driving all four still lets you understeer into the scrub when the caster and camber are as standard .

These boxes should have been an option on ADM L's but in that era it was hard to impress upon people the advantages of AWD road cars . They'd rock up to a car yard on a fine sunny day and try both round the block . They'd come back claiming they couldn't tell the difference and certainly didn't want to pay any more for it .
To be honest most cars that had the option didn't already have the extra diff and shafts in the 2wd version so the price difference was significant .

If Ls were new today and AWD was a $300 option you'd jump at it wouldn't you .

A .

Yes an L with AWD handles like crap by today's standards but it still handles better than an L with only 2WD or PT-4WD!

I can remember when Subaru introduced the 'bubbleback' RX 3 door in the late 1980s, many journalists at the time commented on its better handling compared to the AWD Mazda 323. Rather telling of Subaru at the time Mazda beat them to market with an AWD car!

My 1987 RX Turbo cost around $21 000 new and it was estimated at the time the RXII 3 door (with AWD and dual range) would have cost more than a Vortex at over $30 000! Not economically viable for Subaru at the time and I suppose they knew the Liberty was just around the corner.

[El_Freddo]

My 1987 RX Turbo cost around $21 000 new and it was estimated at the time the RXII 3 door (with AWD and dual range) would have cost more than a Vortex at over $30 000! Not economically viable for Subaru at the time and I suppose they knew the Liberty was just around the corner.

Such a shame that it didn't make it to our shores from the factory - I would LOVE one of these coupes - a WRX sleeper would be out of this world!

Cheers

Bennie

[Gannon]

As stated the EJ has the centre LSD to put power to the rear in the event of front wheel spin - if you by chance get rear wheel spin it will continue to spin as the centre LSD only operates in passing power/torque to the rear wheels when there's a loss of traction.

Um.....no.

The EJ centre LSD reduces a difference of rotation between the front and rear diffs (much like a rear LSD reduces a difference of rotation between the left and right wheels

If the front wheels loose traction, they will spin maybe one or two revolutions before the silicone fluid in the LSD starts to heat and thicken and the rear wheels will begin to turn at the same speed as the front. The same applies if the rear looses traction, the wheels will begin to slip, but the LSD operates and the front wheels turn as the rear wheels do.

It should also be noted that the VLSD provides an amount of static torque to begin with ie. it is partially locked when cold, but upon slippage, the torque increases to maximise traction.

[El_Freddo]

Um.....no.

The EJ centre LSD reduces a difference of rotation between the front and rear diffs (much like a rear LSD reduces a difference of rotation between the left and right wheels

If the front wheels loose traction, they will spin maybe one or two revolutions before the silicone fluid in the LSD starts to heat and thicken and the rear wheels will begin to turn at the same speed as the front. The same applies if the rear looses traction, the wheels will begin to slip, but the LSD operates and the front wheels turn as the rear wheels do.

It should also be noted that the VLSD provides an amount of static torque to begin with ie. it is partially locked when cold, but upon slippage, the torque increases to maximise traction.

Ever seen a centre LSD from a subaru EJ gearbox? The LSD is only built on one side of the diff - thus if you manage rear wheel spin it will be maintained until you gain traction. Its near impossible to induce rear wheel spin anyhow - when you accelerate the weight is shifted to the rear of the vehicle creating better traction of the rear wheels than the front, this is why the front of the vehicle tries to lift and the rear squats down.

I wish I had a photo of said centre diff - Gee showed me one the last time I was over there... This is how I understood it all.

Cheers

Bennie

[D3V1L]

if its a single range box, there is no selector lever. the single range 4wd box has a button on the gear shifter which activates the solonoid for the centre diff. brennyv had one of these boxes.... let me see if i still ahve a picture somewhere

very similar to the 4wd button on the L series autos


davo

[Gannon]

Im sorry Bennie, but the LSD operates both ways.

I have not "seen" the LSD, but i understand how it works.

Here is a picture of 2. Pre 98 on the left, post 98 on the right


From the FSM

Take note of the "Function" section



Yes the LSD part is at one end, but it couples both the output shafts (via the inner left shaft, and the right shaft in the diagram) so it operates in the way i described in my previous post.

If the front wheels slip, the diff binds and equalizes the torque between the front and rear (essentially locking it). The same happens if the rear wheels slip.

[discopotato03]

Yes Superoo you're on the money . You only have to control one of the two side gears because the planet gears are permanently in mesh with both side gears so they can't act independently . If you think about it the mechanical diff lock only locks one side and thats all it needs to make both sides turn at the same speed .
Its not unusual for plate type LSDs to only have a clutch pack on one side , some Nissan Patrols and all OE Nine Inch diffs were like this .

I have the Relevant 87+ L WSM here and it shows all the L transmission options .
People get confused over gearboxes with the vacuum/cable actuators on them . It means its either a lockable AWD box or the push button type part time 4WD box .
If you have a part time dual range transmission like most ADM wagons and all ADM RX's it won't have the vacuum actuator because the transfer selector engages 4WD and low range if desired .

This is how you identify the AWD L box .
Vacuum actuator with the cable curving to the middle height wise of the drivers (RHD) side of the rear extension housing .
Behind where the extension housing bolts to the drivers side of the main split gearbox case is a kind of triangular and angled bracket that supports the business end of the cables outer sheath , this bracket has three bolts mounting it to the extension housing BTW . Behind the bracket the inner cable goes to a turnbuckle kind of length adjuster and a clevis arrangement to the pivot arm . The actual pivot goes into the extension housing down low because the center diff is on the back of the lower or layshaft .
The flat outer side of the vacuum actuator is above and slightly behind the pass side stub and DOJ to look at .

Another way to identify them is that the rear cover plate has bearing to support the back of the center diff and lay shaft - which is also the back of the front diffs pinion in a Subaru .
Now because the rear cover has a lower bearing it needs an aluminium cover plate to seal the hole and in this case it bolts on the lower rear cover plate with five bolts . In other words directly below where the tailshaft slots in .i
Behind this bearing cover is an upside down triangular steel plate with two rearwards facing captive studs and these are for the rear exhaust hanger bracket to mount to with nuts and spring washers . This steel plate actually uses three of the five bolt holes that hold that rear bearing cover in place and you can see two corners of the ally bearing cover sticking out either side with their two extra bolt heads .

If you see a box with the vacuum actuator the other way around and the cable and linkage on the pass side of the box and up high on the extension housing then its a part time push button 4WD box . This is logical because the dog clutch that engages drive to the tailshaft is on the upper rear shaft so thats where is selector mechanism needs to be .

To sum up , vaccy cable low on drivers side of box - AWD .
Cable high to pass side of box - push button PT 4WD .
Mechanical linkage only , gererally part time dual range 4WD

ALL L/Vort and early EJ AWD boxes have the extra lower rear bearing and the triangular steel plate which in L/Vortex's mounts the gearboxes rear exhaust hanger .

A .

[D3V1L]

we have confirmed its a single range 4wd box


dave

[El_Freddo]

we have confirmed its a single range 4wd box

Bugger eh?

That's a shame - IF subarino dave still had hatchie that'd be the icing on the cake I reckon!

Cheers

Bennie

[El_Freddo]

Im sorry Bennie, but the LSD operates both ways.

I have not "seen" the LSD, but i understand how it works.

Here is a picture of 2. Pre 98 on the left, post 98 on the right


From the FSM

Take note of the "Function" section



Yes the LSD part is at one end, but it couples both the output shafts (via the inner left shaft, and the right shaft in the diagram) so it operates in the way i described in my previous post.

If the front wheels slip, the diff binds and equalizes the torque between the front and rear (essentially locking it). The same happens if the rear wheels slip.

Where do I find this file to read up on it more as the next column is cut short at the top...

Cheers

Bennie

[Gannon]

I'll have to copy the pages from the FSM and upload them. I'll try to do them later

Here is a coloured in diagram showing what the internal parts do. (just a quickie using MS Paint)

[El_Freddo]

I'll have to copy the pages from the FSM and upload them. I'll try to do them later

Here is a coloured in diagram showing what the internal parts do. (just a quickie using MS Paint)

That makes a pot load more sense, even if it is coloured in using MS paint!

By the look of that I can't see why a centre diff lock wouldn't be hard to manufacture... The hardest part I reckon would be getting it into the production phase!

Cheers

Bennie

[discopotato03]

They did with the AWD L trans . Manufacturers hate diff locks because the mechanically clueless often enough lock them then drive around on hard surfaces and do damage .

The real clue to how these things work is that the lower or countershaft/layshaft is hollow so it doesn't have to turn with the inner solid pinion shaft but is supported by it .
If you look at the coloured pic note the blue section , the hollow shaft , is driven by the gears on the mainshaft . It drives the would be center diffs hemisphere and therefore the centers planet gears by their support pins .
The blue planet gears drive the red and green side gears , the red being fixed to the solid inner diff pinion shaft and the green driving the transfer gears taking drive up to the shaft the rear tailshaft slides over .
All the viscous coupling does is try to limit the different speeds of each side of the diff center so you don't lose all drive to any of the four driving wheels .
In sedate road use viscous couplings are fine but don't cope very well in competition applications . Once the fluid is well and truly cooked it doesn't work any more . For pure mechanical diffs clutch plate or Torsen centers work better but have some minor side effects .

Anyway back at the locking type AWD boxes . These are different to EJ types in that the forward half or side gear drives the transfer gear and the rear side gear is splined onto the back of the solid inner pinion shaft .
To lock it you simply lock the hollow shaft to the side of the hemisphere with a sliding dog clutch so it direct drives the transfer gears to the rear tailshaft . So instead of the hollow shaft driving the planet gear pins making the planet gears drive the side gears the hollow shaft drives the transfer gear locking the center diff .
Naturally there being two transfer gears they change the direction of rotation so the front differentials pinion turns in the opposite direction to the tailshaft and rear diffs pinion .

Easy as mud , cheers A .

[El_Freddo]

Anyway back at the locking type AWD boxes . These are different to EJ types in that the forward half or side gear drives the transfer gear and the rear side gear is splined onto the back of the solid inner pinion shaft .

Hence why you can't use the locking L's centre diff in an EJ gearbox rear housing...

Subaru clearly decided it was going down the track route with the centre diff design for the EJ gearbox and the production of the RS turbo. Their design became less basic overall and well suited to the tarmac more than they used to be suited to both offroad and tarmac IMO.
As I said, I don't think it would have been too hard for subaru to add the dog "clutch" that locks the front diff's pinion shaft to the lower gearset as it is in the L AWD gearbox to the EJ centre diff... Anyway, that's history now might as well look forward

Cheers

Bennie

[discopotato03]

I don't so much think they went down the "track route" because Liberty's were never what you'd call a good track racer , suspension geometry and weight balance hardly ideal and their gearboxes were a bit fragile .

I think they went to a longer extension housing so they could better support the rear shafts in additional bearings . Also these Subaru gearboxes being split aluminium cases means they don't have much rigidity and with turbo torque tend to twist and misaligned gears want to break teeth off .
Its part of the reason why EJ cars didn't get the shorter low range gears as well .

A .