Clutch Slave Cylinder Question

[Roger UK]

I'm planning to replace my 7M-GE with a 2JZ-GE

I'll be fitting a Mk4 Supra's W58 bellhousing to my W58 . . here's the question:

Will the Mk3 Clutch Slave cylinder fit OK ? (I recently fitted a brand new one) . . or do I have to get one from a Mk4 Supra?

Hope someone can tell me - I've been comparing photos . . . they look different but similar

 

[mjsn1]

If the bolts go into place and you can change gears then it is ok.

 

[Roger UK]

Well I figure that LOL! I'm just trying to suss out everything I need IN ADVANCE so this can be a quick swap over a weekend, without any problems to sort out later or additional parts to order (my Supra is my daily driver, not a hobby car)

Can anyone confirm if it fits and works OK?

 

[destrux]

Hmm... I *think* I used one for a MKIII W58 on mine. You do need the MK4 clutch fork though for sure, it's different.

 

[Roger UK]

Thanks for the heads up about the Clutch release fork destrux . . I did wonder about that

Well the Mk4 Supra Clutch Slave Cylinder has a 2 inch long tube at about 30 degrees going to the bleed nipple (for some reason), whereas the Mk3 one has the bleed nipple straight on the side of the casting. Does that help identify which you have?

Hope someone can tell me if the Mk3 one fits OK (otherwise it's more parts I'll have to buy!)

 

[destrux]

Thinking about it more... the MK4 would be the correct one to use if you didn't have one and needed to buy one. However, I just looked on my car and I have a MK3 slave cylinder on it (and it works fine). So, if you have one it will work.... sort of. Things are never as simple as "will it fit".

The bore diameter is the same (13/16th) according to rockauto. The difference seems to be that the MK4 cylinder sits about ~10mm farther away from the clutch fork. The MKIII slave cylinder has enough depth in the bore that you can push the piston back into the bore ~10mm farther than it was designed to go without a problem. So at first glance it seems to bolt up and work fine... BUT... as the clutch disc wears (and the pressure plate fingers move out as a result) it requires that the slave cylinder piston move back even farther into the bore to accommodate the wear. I don't know if the MKIII slave cylinder has enough depth for that. You might (and I might) find out that when the clutch is half worn out the slave cylinder bottoms out and causes the clutch to slip. The way it sits on my car right now (with a brand new clutch in there) the slave cylinder has about another 5mm of travel till it bottoms out.

I don't know if anyone running this combo (JZ/w58 in a MKIII) has ever actually driven enough on one clutch to wear a clutch disk out to find out if I'm right. Most people end up swapping in an R154 or killing and replacing the clutch when they break the input shaft.

I'm leaving mine in and I'll keep an eye on it. If I ever see it come close to bottoming I'll buy a MK4 cylinder.

 

[Roger UK]

Really appreciate your input on this destrux, thank you

I'm trying to get my head round what you're saying though . . . I gather you have a W58 type clutch (like I will be using) . . . It's just that I know the N/A engines use a PUSH type clutch release and the turbo ones use a PULL . . . does that make a difference?

I always thought that as the clutch wears the piston in the slave cylinder would be further OUT, not in?

Also . . would it help if you filed the mounting holes slightly, to move it sidewise a bit? (I know you'd only gain a few mm, but it might help?)

 

[destrux]

The clutch fingers that the release bearing pushes on move out (away from the flywheel) as the disc wears, the clutch fork is on a pivot, so the slave cylinder end moves the other way (toward the flywheel), which is toward the slave cylinder base. It is the opposite of what you'd expect, but that's how it works with a push type clutch.

A pull type clutch (as in the R154 uses) is the opposite, because the pressure plate fingers move toward the flywheel as wear happens because the pressure plate friction surface is on the same side of the diaphragm spring's fulcrum point as the release bearing.

Filing the holes might help some if it does turn out to be a problem.

 

[suprarx7nut]

I think the best and smartest approach is to buy a brand new mk4 slave from Toyota the week before you do your swap. You can try the mk3 one and if it works, simply return the mk4 one from Toyota. Even if you have to pay a 20% restock fee or something, you'll end up ahead because you'll be prepared to get the job done either way. If you end up with only the mk3 version on hand and have to sloppily modify it to get it to work that weekend, you'll be kicking yourself for not getting the right one straightaway.

My 0.02.