Hydraulic throwout bearing adjustment

[blueovalz]

More for archive usage: A pitfall I've run into on my Mcleod Hydraulic T/O bearing is the installed adjustment. Due to the normal wear on the clutch disc, I've found I must now remove the tranny to re-adjust my T/O bearing. Background and recommendations: The T/O bearing is adjusted by use of a threaded sleeve for proper adjustment. I adjusted my bearing so that it was only a few thousandths of an inch off the fingers of my PP at the "rest" position of the clutch pedal. Unfortunately, I neglected to consider the fact that as the clutch disc wears, the PP fingers (those that when pushed, disengage the clutch) begin extending toward the T/O bearing, and within a short time, these clutch fingers actually began pushing on the T/O bearing itself. When this happens, some of the pressure is taken off of the disc and consequent clutch slippage ensues.

 

In retrospect, I see that I should allow a good bit more clearance at "rest" so that the piston itself does the adjusting, thus as the clutch wears, the piston is pushed rearward forcing fluid back up into the MC (much as what happens when new brake pads are installed and the piston is pushed back into the caliper). My problem at this point is that the piston is pushed as far back as possible, and now preloads the PP, which allows slippage to occur. I did measure the amount of T/O bearing movement with my 3/4" MC at full pedal stroke, and it came out to APROX .4".

[74_5.0L_Z]

My Tilton HTOB specifies a 0.125 to 0.2 inch clearance to allow for disc wear. I run on the tight side, and haven't had any problems. I have replaced the disc three times, but each time before appreciable wear.

 

My setup is at the highest end of the adjustment range of the threaded sleeve to get the 0.125" clearance. I could thread it down to gain more clearance, but am afraid of exceeding the 0.70" allowable total stroke. My clutch disengages about half-way through the pedal travel. My set-up includes the following parts.

 

Tilton 74-875U master cylinder (.875 diameter)

Tilton 61-601 Hydraulic Throw-out Bearing

Tilton 61-612 Adapter

King Cobra Clutch (5.0L Ford)

[blueovalz]

Thanks for the reply. I was also at the end of the threaded sleeve, and was concerned that the threaded sleeve (engaging too few threads in my opinion for a race clutch) may give way and strip the threads, so in my infinite wisdom, I machined a 1/4" spacer to be added the the factory supplied 1" spacer, so that I could engage more of the threads behind this high force PP. Well, I guess I went too far forward when I did this. Thanks for the specs there, at least I've now got some kind of reference to go by when I pull this and put it together correctly.

[74_5.0L_Z]

Bringing this one back from the dead because someone asked a question regard installation of the T5.

This is my current set-up:

Tilton 75-875U master cylinder (.875 diameter)

Tilton 60-6104 Hydraulic Throw-out Bearing

Tilton 61-612 Adapter

King Cobra Clutch (5.0L Ford)

Centerforce Dual Friction disc

Fidanza Aluminum Flywheel

Steeda Tri-Ax Shifter

I have also upgraded my T5.  I have the G-Force gears and main shaft with the following gear ratios:

1st 2.94

2nd 1.94

3rd 1.33

4th 1.0

5th 0.80

If I were to do it again, I would just contact Astro Performance and get there A5 with the 0.80 fifth gear.

I have the engine and transmission out of the car right now for a rebuild of the engine.  I plan to upgrade the pressure plate to the Centerforce LMC aluminum unit.