Dished Flywheel + Getrag + Clutch Fork Questions

[Cameron]

Ran into a bit of a roadblock today -- was gonna drop in the motor/trans but I noticed something after I bolted the trans to the motor....

As seen in my project thread (see sig for link) I'm using a dished LH 2.4 flywheel and a spec clutch to go with the Getrag conversion I'm doing at the same time. Well, I was somewhat nervous about this exact thing happening and it turns out I was right. I modified my clutch fork, which is the -84 style fork to work w/ the BMW throw out bearing. See pics below:

https://www.ipdusa.com/uploads/images_blog_slideshow/fullsize_389.jpg
https://www.ipdusa.com/uploads/images_blog/219.jpg

See this post for details/pictures of the bearing and the fork: http://forums.turbobricks.com/showpost.php?p=2374354&postcount=244

The overall "height" -- how far forward the face of the throw out bearing -- w/ the BMW bearing on the fork is only slightly "taller" than the fork w/ the Volvo throw out bearing on there. However, that fork/bearing combo was originally being used on a flat flywheel... So when I bolt this all together with the dished flywheel/clutch combo the clutch fork doesn't have enough room to back all the way off the fingers of the pressure plate. i.e. w/ the back of the fork pushed all the way back against the opening on the bellhousing, the release bearing is still against the pressure plate fingers. Clutch is totally engaged, but if I were to leave it this way, the throw out bearing will never totally disengage and therefore be constantly spinning -- no go. :grrr: So I'm guessing that the overall stack height of the dished flywheel/clutch combo must be taller than the stack height of the flat flywheel/clutch?

From here I figure I have 2 options -- 1 = get later style clutch fork and modify it to fit the BMW bearing like so seen in 740ALT's pic here, which appears to be the identical throw out bearing I'm using:

http://k53.pbase.com/v3/75/540175/2/50798030.IMG_1674.jpg
http://k43.pbase.com/v3/75/540175/2/50798022.IMG_1672.jpg
http://i.pbase.com/v3/75/540175/2/50798033.IMG_1670.jpg

^^Looks like using that style fork allows the throw out bearing to sit "shorter" or closer back towards the trans.

Option 2 = try to modify what I've got. I think the only way I can sit the bearing further down into the clutch fork would be to chop off the "ears" of the release bearing that stick out from the side of it that are currently resting on the face of the fork. That would give me approx. 1/4" or so more room. I just don't know if that'll be enough.

So what say you TBricks Getrag vets? Is the later fork the better option? That's the way I'm leaning right now. But that means more parts hunting.

[Group A]

I'm not going to be around, but I'll leave the later style arm on the metal table out front in case you need it. We usually file the opening to fit the t/o bearing.

Clutch kit height is usually the same from flat to dished flywheel though, so not sure whats going on with your set-up.

Arm is there if you need it.

[Cameron]

That is awesome -- thank you very much! :)

I was thinking the clutch stack height was the same too, but I didn't have a flat flywheel/clutch sitting around any more to compare it to since I gave the one I had to TFest. Must be a difference in the arm height. We'll see I guess when I come pick up that fork from your shop.

I'll cruise over there right now. Again, much appreciated!

[sbabbs]

I used the 740 hydrolic fork and it is way smaller and only comes in from one side and the pivot ball is on the other side. I just had to grind it out a little so it fit around the bmw throw out bearing. It works fine, so seems like you are on track with getting the clutch fork from a dog dish car, hydrolic 740 style or cable 240 style long as it's a dog dish flywheel should work hogged out to fit the BMW bearing. The later 240's in 89 used the dog dish with lh2.4 and cable fork.

Simon

[Cameron]

Got the later fork from Patrick - again, thanks man - really helped me out! Looks like this should fix it.

Height of the fork is about the same, but the later style fork has a bend at the cable end of the fork that'll bring it further forward in the bellhousing window. Tomorrow it gets swapped.

[945ti]

The stack height is the same between flat and dished if we are comparing stock sachs clutches to stock sachs clutches in stock 240s with non or minimally machined flywheels. Whether the spec thing is or isn't who knows...I'd measure that for myownself.

You can also grind the pivot stud down a fair bit on the opposite side to help with clearance and angularity of the stock fork. With the stock pressure plate and stock thickness clutch disc, the throwout bearing will hit the volvo bellhousing at the back if you don't bore/saw/cut a nice large hole in the back of the bellhousing regardless of fork choice.

I chose to center bore the bellhousing to the OD of the BMW throwout bearing sleeve and grind the volvo bellhousing down years ago when I did up my getrag adaptation. I would use a centering ring and cut out the middle of the volvo bell had I to do it over again...less fussy, easier to mod the bell and more serviceable.

It isn't the riding of the pressure plate that I'd worry about. The stock hydraulic release bearing does that. It is more the clutch not releasing all the way, which is never good or easy on parts. You may wish to add a little reinforcement to the fork after you have modified it. You may also want to re-create the smooth "humps" that the stock late model volvo release bearing slides on so as to not side-load the bearing or slide it rides on as much.

I wish I had pictures of what I have done in the past on both cable and hydraulic clutch getrags. Oh well.

[MikeJr.]

http://k53.pbase.com/v3/75/540175/2/50798030.IMG_1674.jpg
http://k43.pbase.com/v3/75/540175/2/50798022.IMG_1672.jpg

Hey thats my hand. :lol: Those pics are from my install. I don't think that Mike and I knew at the time that that was the later clutch fork. I did have to grind out the inside a bid to allow room for the bmw TOB. I suggest using a return spring on the clutch fork like some applications have that way you have constant pull back on the fork. Now I'm not using a spring but I have also gone threw 3 clutches since the install. When I buy my 4th and final clutch I plan on adding a spring.

[MikeJr.]

Or you could just get one of these http://www.racingclutches.com/product.phtml?p=53&cat_key=89 :oogle:

[Captain Bondo]

Just remember that this problem gets worse the more the clutch wears. So not only do you need freeplay in the release arm now, you need enough clear that you can have freeplay after the clutch beds in and after it wears.

I would want a good 1/2" of total available free play so you can adjjust the cable and have some "in reserve" for future adjustment.

Or, go hydraulic! All of the cool kids are doing it!:lol::-P

[maxman142001]

Yeah that Hydro setup is very cool...i might go this route for the Getrag

[Cameron]

Hydraulic would be the preference for sure -- but not yet. I just want to get this thing going. Hydraulic would be fun for down the line, but I don't want to add another layer to this build just yet.

I just pulled the trans back off the motor to swap forks. Upon taking it apart I found that with that earlier fork, w/ the back of it resting on the back of the bellhousing window it was juuuuuust about to fully release from the pressure plate.

With both forks on the bench you can clearly see the difference in "height" of the arm of the fork -- it's about an inch or so (I'll post up a couple pics for reference later today). Which means that I should have about that much "play" with the later style fork from when the bearing releases from the pressure plate and when the back of the arm would "bottom out" -- makes me much happier.

Off to go hot out the later fork to accept the BMW release bearing and then put it all back together again -- weeeeee!

[Cameron]

Discovered a couple things today I didn't know. First is the different clutch fork. Later style one (the rear one in the pic) has that extra bend at the cable end allowing further travel back. See pic:

https://www.ipdusa.com/uploads/images_blog/434.jpg

So that explains the issue I was having w/ the fork bottoming out at the back of the bellhousing window. Now I figure it should all work fine. So I ground down the opening to accept the BMW throw out bearing and bolted it back into the bellhousing, put it all back together. Plenty of room between the back of the fork and the back of the bellhousing window now, but fork can't move all the way back and bearing is still riding on the PP fingers. :grrr:

Take it back apart and check out why the fork won't go all the way to the back of the window and I see that it's hitting some of the "baffling" on the back of the inside of the bellhousing. Then I looked back at some pics from other Getrag conversions and realized my bellhousing looked different than the others I'd seen conversions on. The bellhousing I'm using is from the M46 that was on my '80 wagon from the factory. I also just so happened to have a later bellhousing off a 740 in the garage so I compared them. Lo and behold:

https://www.ipdusa.com/uploads/images_blog/435.jpg

So that was the 2nd new thing I learned today -- all the M46 bellhousings are not the same. The early one I'm using has a ton more material at the back where it meets the trans. See all the extra meatiness on the back of the inside of the earlier bellhousing? The later bellhousing (which I'm guessing changed at the same time as the fork?) is much thinner at the back and doesn't have all the extra baffling/lumps at the back. Because of this the back of the fork, in the middle-ish of it was hitting the lumps and therefore the fork couldn't move all the way back and couldn't disengage completely from the clutch.

Since I didn't want to spend the time (and didn't have the proper hole saw handy) to modify the later bellhousing I decided just to cut a couple notches off the back of the fork to allow it to clear all the lumps and back all the way back to the back of the bellhousing. To be sure there wasn't any depth difference in the bellhousing that might **** up something else I measured it on each to be sure:

Later, non-lumped, bellhousing:
https://www.ipdusa.com/uploads/images_blog/437.jpg

Earlier, lumped, bellhousing:
https://www.ipdusa.com/uploads/images_blog/438.jpg


Anyway, after the fork was notched to clear the lumps and it could back all the way off, I had a good 1/2" - 3/4" freeplay from PP engagement to fork bottoming out at the back of the bellhousing window. So success in the end I suppose.