Which throwout bearing with twin disk?

[WhatsADSM]

Okay all I need your help.

I have been fighting this transmission whine through 2 transmissions now, and I finally decided to go to the Z32 hybrid trans route. However when I took my existing rb25 trans out I noticed the throwout bearing is pretty much shot.

Now normally this wouldn't be a big issue, however I have the HKS twin disk, which is not only a japan only kit, but IIRC also discontinued by HKS. So my question is, has anyone tried a standard z32 throwout bearing with their twin disk (possibly even an HKS)?

Otherwise I'm not sure what to do. I really can't afford to go out and buy a new twin disk kit just because my throwout bearing is bad.

[julio]

Is the throw out bearing that different than a normal nissan unit? I'm trying to visualize what could be different between the two, but I could only really imagine the thickness of the units differing. I can't imagine the bearing contact circle being much different. I would say just pick up a spare 300zx unit and compare if you haven't already.

[l0nestar]

Jables might be able to offer some assistance if you can compare pictures of a SPEC TOB vs your HK$.

[WhatsADSM]

Hmm so I know I may catch a few flames for this, but I think I am going to just try the stock TOB (i.e. z32).

The HKS is definately different, however it isn't a TON different. Basic premise is that the location of contact on the HKS throwout bearing is closer to the center of the bearing, where as the stock TOB the contact point is more towards the outside.

So what that means is that when I use the stock bearing it will now contact the pressure plate just a little closer on the outside of the pressure plate fingers. Once the trans was in, I gave the clutch a few pushes and it seemed okay. The top inch or so of the petal seemed a little more dead than before but otherwise it seemed fine. I can't imagine it would be that big of a deal, but I will be taking it a little easy when I first roll the car out just to make sure everything seems okay. Because next weekend I actually have my favorite road racing event of the year so I will be beating on it pretty good then.

Here are some pics I snapped of the two TOBs next to each other. Standard z32/rb25 on the left, HKS on the right:

[gawdzilla]

if it's any reassurance, i've been using the same clutch (exedy triple plate) and TOB (oem nissan z32 na) for the life of my motor and two transmissions (first one i killed 3rd gear). haven't had any problems. last time i had it apart everything looked great. the shape difference of the TOB might be an issue for you, but i would not worry about the durability of the oem nissan stuff. then again, the exedy TOB (if there even is one) might be different than what i'm running. but i've never seen one to know any better

[julio]

Yea, that extra dead feeling of the top inch or so of the pedal is due in part to bearing contact circle having a larger diameter. The smaller HKS unit has better mechanical advantage over the stock z32 by being able to contact the pressure plate fingers at a further point, giving it more torque/same clutch line pressure. I'm sure rigidity also comes into play as the pressure plate fingers are basically cantilevers.

[WhatsADSM]

Yea, that extra dead feeling of the top inch or so of the pedal is due in part to bearing contact circle having a larger diameter. The smaller HKS unit has better mechanical advantage over the stock z32 by being able to contact the pressure plate fingers at a further point, giving it more torque/same clutch line pressure. I'm sure rigidity also comes into play as the pressure plate fingers are basically cantilevers.

Yea after looking everything over I was expecting a harder pedal pressure due to less mechanical advantage by pushing at a different point in the fulcrum. (I am equally a little worried about over extending now as well since it is pushing differently but I digress). I guess I am still a little confused as to why at the very top it feels like there is basically nothing then I feel what seems to be normal pedal feel... Julio why exactly would you expect the top of the pedal to feel dead?

I almost wonder if it is worthwhile to just bleed the clutch lines as it essentially feels like there is a small pocket of air there or something.

[julio]

Yea, that extra dead feeling of the top inch or so of the pedal is due in part to bearing contact circle having a larger diameter. The smaller HKS unit has better mechanical advantage over the stock z32 by being able to contact the pressure plate fingers at a further point, giving it more torque/same clutch line pressure. I'm sure rigidity also comes into play as the pressure plate fingers are basically cantilevers.

Yea after looking everything over I was expecting a harder pedal pressure due to less mechanical advantage by pushing at a different point in the fulcrum. (I am equally a little worried about over extending now as well since it is pushing differently but I digress). I guess I am still a little confused as to why at the very top it feels like there is basically nothing then I feel what seems to be normal pedal feel... Julio why exactly would you expect the top of the pedal to feel dead?

I almost wonder if it is worthwhile to just bleed the clutch lines as it essentially feels like there is a small pocket of air there or something.

I think I misread your post because I would assume it to have a harder pedal feel all around. Is there any play in the clutch fork/slave cylinder when in neutral? Perhaps bleeding would be a good idea. Easiest bleed too if you ask me.

[WhatsADSM]

Just wanted to update this thread for those who search. I just got back from my 2 day road racing event and the clutch and TOB performed great. Only thing I noticed was a *slightly* heavier pedal feel, but otherwise everything worked. So unless I update this thread later on to say that something died prematurely then I'd assume it's okay to use the stock TOB with the HK$ twin disk.