Internal Clutch Slave - Clutch is Slipping

It is likely the McLeod hydraulic throwout bearing conversion done by Dennis. I have it on 2511. Works fine but is a PITA getting it properly adjusted. And Yep, you get to pull everything apart if it needs adjusting  

Larry

I also have the hydraulic throw out bearing and it is a pain to adjust just for that reason, no way to adjust it except to pull everything

This is helpful.  Will I be adding or removing shims?

Do you feel any free play before the clutch begins to release? If you do, T/O bearing adjustment isn't your problem. Either way, the ZF needs to come out. At that point your problem should be fairly obvious. 

Adjusting the position of the throwout bearing is not done with shims.

it is done with male and female threads  

in the photo below the far right piece is a spacer notched to fit over the input shaft tube mounting bolts.

next is an aluminum piece that slides over the input shaft tube and has full length male threads.

The next piece is the piston assembly and it has matching female threads.

The bearing is a press fit onto the piston assembly snout.

that should give you a better idea of what to expect once you pull things apart

Larry

...You are Not going to like hearing this, and this has nothing to do with a slipping clutch...

FWIW, In the Photo, the Half-Shaft Flange Mounting BOLTS are Installed from the Wrong Direction. YES! It makes a Difference. The physics of Bolt Fasteners dictates..."The Bolt HEAD Must contact with 'The Most Rigid Base' "*. That Base would be the Transaxle Drive Flange. The Bolts are to be Installed from 'Behind' the Drive Flange. Since you will be pulling everything apart, it will be an opportunity to correct this. Not just My Opinion, just Good Engineering.

* And in the case of a 'Rotating Assembly', such as a Helicopter 'Rotor-Head', the Bolt Head Always Points in the Direction of Rotation. If, in the Worst-Case Scenario, the Nut should vibrate Off, the Bolt would Stay in position.

The Praise: It looks as if You have Eliminated the 'Split-Washers'! This is Good!! I, also did this, First Thing! The 'Split Washer' is a Hardened 'Spring'. I Have seen more than One, Break, Fall Out, and the Bolt Immediately becomes LOOSE, you don't need to Guess, what Happens Next!

This is a 'Heads-Up', for All those who care to listen.

MJ

Thank you Marlin.  I will flip the bolts as you suggest.

The clutch is Centerforce.  I am not sure yet about the maker of the hydraulic throw out bearing.

Here is a closeup of the hydraulic throw out bearing

I can't tell you who the manufacturer is but I can tell you who it isn't. It is not a McLeod. Doesn't look like a Tilton or a Ram either.

I would have to say that what is showing in Steve’s photograph is an early version of the McLeod throwout bearing  

My experience started over 20 years ago with the McLeod throwout bearing installed by Dennis in the mid-1990s. My first rebuild went just fine. My second rebuild was difficult  

McLeod customer support is poor, and that is putting it mildly. Their rebuild kit for these bearings has retained the same part number despite being upgraded at least two times. I learned this when I ordered my second rebuild kit and what they sent had no relation to what was currently installed, having previously used  a rebuild kit with the exact same part number. Turns out they had changed the design a little bit but kept the same part number for a rebuild kit. 😳🤷‍♂️ I had to upgrade to a new bearing carrier and the larger bearing.

you’ll find McLeod cannot provide a rebuild kit for the bearing shown in Steve’s photo. He will have to do as I did and upgrade to a newer unit. IIRC they did give me a little bit of credit when I returned the early version

Larry

Early version  note the bearing size

late - current?? - version  note larger bearing

Larry

My existing throw out bearing is not leaking.  My only problem is that the clutch is slipping, primarily when accelerating on the freeway.  Wilkinson looked into the inspection cutout on the bell housing and thought there was plenty of clutch disc.    The throwout bearing itself seems healthy.  My plan is to set the clearance for the bearing and reassemble it after cleaning everything and putting in new shaft seals and side gaskets on the ZF.  I will be taking this all out later for an engine rebuild and just want to get the clutch slip and ZF drips fixed for the time being.

Steve, I stand corrected. Here’s what my McLeod hydraulic T/O bearing looks like.

David, no worries.  As Larry stated, this setup has evolved over the years.

I made good progress today and the resealed ZF is back in the car.  At this point there is too much free travel in the pedal and I will need to decrease the throwout bearing clearance.  I assumed I would not get it correct the first time and everything is minimally assembled.  Nonetheless, the transmission and hydraulic line have to come off to make the adjustment.  After reassembly the slave has to be bled to remove air.  Heavy lifting is required to adjust this clutch setup.

Problem is, the throwout's free clearance CHANGES WITH TEMPERATURE. As with valve lash when you adjust cold, clearance decreases with all concentric throwouts when everything is warmed up, and that takes about 30 minutes of moderate driving on the road. 

I built one out of a Tilton dirt track racing assembly back in the mid-'90s, and you need far more cold clearance than you'd think. The Tilton throwout carrier is internally fine-threaded and has a threaded ZF nose piece, so to adjust it, you disconnect the lines and rotate it, then re-bleed. It's held in place with a stripper allen-bolt, not just hanging on the lines. Once adjusted, it stays there. Haven't readjusted in 20 years. Tilton does not build one for a ZF.

The good news is, you only need to slide the ZF backwards for access while it lays on the lower subframe rails. One person can do this without an engine crane- no need to completely remove the 155 lb lump. You may need to unbolt the A/C condenser ass'y and swing it out of the way so as to slide the ZF back far enough. No need to disconnect the A/C. Good luck.

Thank you Jack.  That is helpful.

Jack, I’m surprised you didn’t mention that replacing the ZF’s side mount studs with bolts makes sliding it back much easier.

David, good point and I have already made the change to the ZF.

True- its one of the first mods I did after pulling the ZF the first or second time. Well worth doing.

You could also use M10 Allen head set screws.

On the theme of modifying the rear ZF mounts, these photos show my approach when reassembling 2511.

It is based on the OEM system used on the later 9000 series cars.

Mounts were cut from 3” square tube. Fabricated brackets with back-welded nuts welded and molded into chassis.

Larry

I contacted McLeod customer support and got a better understanding of this hydraulic throwout bearing.  He explained that it is self adjusting (to a point) and when installed dry with .100" clearance, then refilled with fluid, and finally purged of all air in the system then there is never any clutch pedal free play.  If the clutch disc wears more than .100" then the pressure plate may not fully deploy and the clutch could slip.  My car is almost back together and I will find out soon if resetting the dry clearance fixes my problem with clutch slip.  

It looks like this effort is a success.  I took it out for a test drive and could not get the clutch to slip.  I still need to test it on the freeway and plan to do so this weekend when the traffic patterns are different.

Larry - those mounts look very nice !

Marlin Jack - Blow you , now I have to turn all my half shaft bolts around !! Thanks for the heads up. Which way are the outboard ones supposed to go ?

@lf-tp2511 posted:

I would have to say that what is showing in Steve’s photograph is an early version of the McLeod throwout bearing  

My experience started over 20 years ago with the McLeod throwout bearing installed by Dennis in the mid-1990s. My first rebuild went just fine. My second rebuild was difficult  

McLeod customer support is poor, and that is putting it mildly. Their rebuild kit for these bearings has retained the same part number despite being upgraded at least two times. I learned this when I ordered my second rebuild kit and what they sent had no relation to what was currently installed, having previously used  a rebuild kit with the exact same part number. Turns out they had changed the design a little bit but kept the same part number for a rebuild kit. 😳🤷‍♂️ I had to upgrade to a new bearing carrier and the larger bearing.

you’ll find McLeod cannot provide a rebuild kit for the bearing shown in Steve’s photo. He will have to do as I did and upgrade to a newer unit. IIRC they did give me a little bit of credit when I returned the early version

Larry

Larry,

When you went to rebuild your throwout bearing the second time and they sent you the wrong kit, did you contemplate just buying o-rings for the rebuild?  It looks like the kit is comprised of just five o-rings.  My hydraulic throwout bearing is not leaking now but it is 25 years old.  It is working well and adjusted correctly. When the time comes I am hoping to avoid the installation of a brand new setup when I might be able to just replace o-rings.

Thank you, Steve

I don’t doubt that the O-rings could be sourced commercially rather than through McLeod.

Assuming the used O-rings are still intact you could probably determine cross-section and diameter dimensions, and source appropriate replacement O-rings.

I imagine the same could be said for finding a replacement bearing??

I am pretty sure I saved all my old pieces, I could take some measurements and then send them your way if you would like.

now that I think about it I should probably order a replacement bearing and rebuild kit before they again change the design.

Larry

Hi Larry,

It would be helpful to get measurements of your old o-rings and the bearing.  That way I can get the parts to rebuild it ahead of time and minimize down time for the car.

Thanks, Steve

Steve, are you sure that the McLeod hydraulic T/O bearing is compatible with your Centerforce clutch pressure plate? I seem to recall Dennis Quella saying the counterweights had to be removed from the Centerforce PP, in order for the T/O bearing to work properly. That being said, I can see no signs of contact in your photos  but it might be worth a phone call to Dennis.

Hi David,

It has been setup this way since 1995 or so.  I think the setup was provided by Dennis.  The car also has Dennis' radiator (by Ron Davis) along with Dennis' 10 quart aluminum oil pan.  When I first got the car the clutch was very unfriendly and now it is just the opposite.  The clutch was very abrupt and it was easy to stall the car.  I improved it by removing the clutch effort reduction mechanisms (it is now like an early Pantera) and adjusted the McLeod throwout bearing to get rid of clutch slip.  The clutch now requires minimal effort, is very predictable, and readily holds the engine's power.