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Ok, we are about to put the hi/lo box in the WRX soon but I want to retain the hydraulics as I can get a much stronger pressure plate (re-built MY09 3000 lb which will fit the WRX flywheel) which would kill a cable set up fairly quickly so has anyone adapted the later hydraulic slave cylinder to the early (92) box? Also much easier as everything is already there so no pedal change etc.
Pics diagrams would be nice too. Guess I should have searched....oh well, too late now, not wasting all this writing

Dunno f it helps at all Tom, but our 03 Foz has hydraulic clutch. It looks like the same set up as the rex but mounted the engine side of the clutch fork so it pushes toward the back of the car. Looks like it pretty much bolts to the engine. Welcome to come have a look if you want.

Yeah Corry, that's what we are thinking of doing, just be nice if someone had done it or maybe I'll have to find the Foz/Outback slave if it mounts better or has a different throw length, still got to wait for the LSD to come from the US before we can do too much, hopefully soon.

i have compared the cable clutch on my '93 Lib to the hydraulic clutch on my '98 Foz and they are interchangeable. To make it fit I had to move the pivot ball for the clutch fork, but the threaded hole is there in the gearbox housing. They are both non turbo so that means push clutch... I think?

the forrie hydraulic clutch pedal even bolts into the Lib too...

Hydraulic is push, cable is pull so the slave really needs to be mounted on the opposite side so it moves the fork in the same direction, I have all the cable stuff, I just don't want to use it for reliability, I'm sure we'll work something out remembering mine is turbo.

The "push" and "pull" terms refer to what the clutch fork does inside the bellhousing.
There are really three different types of clutch in EJ based Subarus.

You really need to use whatever setup suits the gearbox to ensure it works properly.

1 - Clutch cable setup (push type) n/a
Found in early Libs.
I think this is the best thing for you to use in this case. You can easily get the pressure plate clamping pressure upgraded by customising the springs and spring angle. I've had a standard L series push clutch (cable operated) upgraded in this way and it's held an EJ20 turbo no problem, so did Alex in Wanky Wagon.
Note - this clutch cable setup is essentially the same as L series overall, but the cable itself and fittings etc are all different and don't bolt straight into an L series.

2 - Hydraulic (push type) n/a
This is found in some Outbacks and I think maybe some Foresters. Pretty much the same as the clutch cable setup clutch/pressure plate wise but it's operated by a hydraulic master/slave cylinder setup. It's completely different to the master/slave setup in turbo cars though.

3 - Hydraulic turbo (pull type) turbo
This is found in all Turbo Subarus. The clutch fork works in an entirely different way. It pivots on a rod which passes through the fork. This is also operated by a hydraulic master / slave cylinder but the slave cylinder is mounted the opposite way around.

A quick inspection of the bellhousings of a turbo and non-turbo gearbox both removed from cars and sitting side by side on the floor will show the differences.

You can't use a pull type hydraulic system on a gearbox designed for a push type system (either cable or hydraulic-push) because the bell housing casting is totally different. Doesn't have the mounting facility for the pivot rod, or mounting for the slave cylinder etc. I've heard of a push-to-pull conversion adaptor of some sort but it was very very expensive and probably impossible to get hold of.

The general rule of thumb I've found to be tried and tested is always use the original clutch setup to suit the gearbox.

My advice is to use the standard cable system that suits the gearbox, with the standard clutch setup and get the pressure plate upgraded by AutoClutch in Osborne Park to a higher clamping pressure to suit the power of the engine. Get the flywheel (the n/a one) machined and get a new clutch disc at the same time.
This will absolutely work.

Note - a clutch cable setup should be perfectly fine for reliability, even with the modified pressure plate with increased clamping pressure. I recommend starting with a brand new clutch cable though just incase an older one might be worn.

Another way to go would be to put the contents of your gearbox into a turbo housing. This would allow using a turbo clutch setup, and hydraulic setup, which in turn allows you to use a 100% factory turbo clutch. Will hold the power of course, and nothing is being *customised* so should be the most reliable. HOWEVER....you will need some custom machining done, because of course the turbo gearbox housing will not accommodate the dual range system. This is pretty specialised work, I am not sure exactly what is involved, but it was chucked in the too hard basket for me. Perhaps AlpineRaven has some ideas about this.

It was the guy from AutoClutch who suggested trying to go for the hydraulic set up because he can supply a much stronger clutch doing it that way, we spent about an hour nutting out the best set up the other day, that's when he came up with the 09 Impreza clutch idea but using hydraulics set up on a bracket opposing the fork so it pushed from in front instead of pulling from behind like the cable, I'd much rather have 3,000 lb hydraulic against a 2,400 lb cable which is as strong as he would go without risking reliability problems, I'll have a look at what hydraulic set up's the Foz & OB use.
I have absolutely everything needed for a cable set up inc a new flywheel so I'm not trying to scrimp, I just want it strong.
P.S. the 09 n/a clutch is the same type of clutch that is used in the hi/lo box, it's just a beefier set up & fits the WRX flywheel so the same bearing and fork as my 92 hi/lo Lib box which was obviously recently re-conditioned and luckily is in mint condition.

What happened with this setup in the end? Also how have you found the front LSD, it was a OBX helical?

I'm looking at exactly the same thing with a Gen1 box in a hydraulic car. I've notived my Gen1 box has a the mounting points for the same slave cylinder that sits on my turbo box and a second hole for a different fork pivot point, but obviously it doesn't have provisions for the pin/dowel type fork. Like you i'd prefer to keep the hydraulic setup thats in my car already.

Cheers,
Rhys

Hey, we pissed around with a Nissan slave (same size but better shape) on the opposite side for about 4 hours & couldn't get the throw right so gave up & whacked the cable clutch pedal etc in and so far it's been fine and not anywhere near as heavy as expected but I now have a spare cable to carry "just in case". As far as the diff goes it's brilliant, no noise & very little torque steer, it just keeps going in the soft shit till it's sitting on the bash plate....Pic below lol. I'm still after a 12 or 15kg center diff & if Tazza's rear works one of them too.

d_generate wrote: & if Tazza's rear works one of them too.

No if - when

I'll be up for one of those for sure!!

Cheers

Bennie