mc leod 1400 series hydraulic throw out bearing zf

McLeod 1400 Series Hydraulic Throw Out Bearing ZF Install

2/22/2015 1 Coffield


For a little background, I needed an aluminum flywheel and clutch for my new engine build. I had heard McLeod had a Pantera “kit” and also a Hydraulic Throw Out Bearing (TOB) tailored for the Pantera so I gave them a call to see what they had and ask a few questions because I’ve never had very good luck with “kits” for the Pantera. I can’t say I was totally comfortable with all the answers but the McLeod tech support guy claimed to have been to RBT’s shop and know the ZF well. I’ve had a generally favorable impression of McLeod products over the years so I purchased a McLeod aluminum flywheel (164t neutral/internal balance), RST Twin Disc clutch, and hydraulic TOB . They sent me to Summit for the purchase because McLeod will not sell direct. The part numbers and prices are on the following page…not inexpensive. There is nothing unique about the Flywheel and Clutch. The RST is low enough profile that it doesn’t have the ZF bell housing interference problems some other sbf clutches do so these are off the shelf items. The TOB was supposed to have a spacer (PN 1428) that adapted the 1400 series McLeod slip on TOB for the ZF input shaft collar. It took me three phone calls and three additional weeks after the initial shipment to finally get the spacer shipped to me and when it arrived, it wasn’t made correctly. The following is what I did to adapt the 1400 Series TOB to the Pantera -2 ZF.

Here was the McLeod Pantera TOB “kit” as received. It had a couple feet of bleed hose, a short section of feed hose, the TOB, but no spacer. This is a “slip on”. It appeared that the hoses were the only thing that prevented the assembly from rotating against bearing friction. McLeod tech support said the O-rings inside the adjuster were sufficient to prevent this so I asked what kept the TOB from rotating on the threads of the adjusting bushing…..the answer was they had thousands in the field and they worked fine. I chose a different approach which is described in in the following slides.


The cross shaft needs to be removed from the ZF. When you drive the roll pins out make sure you lift the actuator and drive them downward. I measured and if you drive them the wrong direction they will not clear the rear housing. After you remove the shaft you can knock out the needle bearings and cap with a suitable diameter socket or plug and just tap them out.


When I received the 1428 “Pantera” spacer from McLeod, I was disappointed. To work properly, it just needed to have the right ID to slip over the ZF input shaft collar (it did), be the right height (it was not), and have the bolt head reliefs clocked properly to straddle the heads on the input shaft collar mounting bolt (it was not). At this point I’d had about all the help I could stand from the manufacturer and just resolved to make my own spacer incorporating an anti-rotation feature for the TOB, and taking nothing else for granted.

ZF input shaft collar McLeod 1428 Spacer Re-engineering spacer


Hydraulic ZF Bulkhead Bushings and TOB Spacer


I like to use these tolerance rings for light press fits. They’re essentially just a piece of corrugated stainless steel formed into a ring that acts like a radial spring and allows for looser tolerance. If you’re a good machinist you can just machine your own degree of interference fit with the ZF cross shaft bore.


Tolerance ring

These are manufactured by USA Tolerance Ring. Tough to find a source to buy 2 pieces but McMaster Car has a similar item 2896K11. They call them “Shim Rings”, 38/608,21.99mm Outside Diameter. It needs to be re-shaped with the raised dimples outward. This works fine because the fit is controlled on the compressed height of the corrugations.

Here’s the TOB with the simple anti-rotation/positive stop I attached. I just picked up two of the existing McLeod fasteners to secure it.

5/16-18 Cap Screw

Anti-rotation positive stop

Several O-rings install into these internal grooves in the adjusting bushing. They do little more than keep the TOB axially located on the input shaft collar when the clutch is not actuated.


Spacer on bearing and engaging positive stop block.

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Here’s the spacer installed on input shaft. The bolt head reliefs on the rear of the spacer straddle the input shaft collar bolt heads allowing it to seat on the collar flange and prevent rotation. The TOB with stop block then slides on and can still be adjusted axially with the TOB adjusting bushing if needed.

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Install bulkhead bushings for the hydraulic lines

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Here is the finished installation. 1/8” NPT to -4 AN adapters were installed in the bulkhead bushings then ¼” brake lines bent and flared to suit. The -4 fittings on the TOB rotate and can be positioned to point either direction. I tried to add a few bends for some strain relief and ability to slightly reshape them for a little axial adjustment if ever need. The hydraulic feed port is on bottom and the bleed port on top.

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The other side has a typical bleeder fitting with a hose barb installed for easy access and bleeding.

Bleeder

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Note: .734” was the proper spacer thickness for my installation with the RST MCL-563200 and -2 Pantera ZF bell housing. Different thicknesses may be required for different combinations. –Always measure.

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Since my experience thus far with the OE hadn’t been confidence building, I decided to put my faith in what I could measure myself. Upon disassembly and inspection, I will say the McLeod TOB appears to be a quality part. It’s a constant run design but according to McLeod relaxes about .010” when not actuated. It needs to be installed such that there is initially .100-.150” clearance between the bearing face and clutch fingers/diaphragm because as the clutch wears the clutch actuator grows toward the TOB. Initially it self adjusts to take up the gap in the installed height. After self adjustment the master cylinder should not be completely filled as clutch wear also returns fluid to the master cylinder. Measuring the annular piston I found it has an effective area about .884”. The actuator has a total stroke of 11/16”. The RST (and most other) clutches need about ½” of stroke to fully and reliably disengage the clutch. If I had to fault the TOB, the ring on the back of the piston looks pretty fragile and there is no means for controlling stroke and/or preventing either the TOB or Clutch from being over stroked. This will need to be addressed by the master cylinder and pedal.

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Annular Piston .882 sq. in

McLeod recommends a .75” bore master cylinder for the 1400 Series TOB. This makes sense because the effective area of a .75” bore master cylinder is .442 square inches which is miraculously half the effective area of the TOB. Since most master cylinders have about 1” maximum stroke this means a .75” bore MC is the minimum diameter needed to get the required ½” stroke of the clutch with the TOB. Since the neither the TOB piston nor clutch has a positive stop I will either build the stop into the MC rod or the pedal. I plan on bench testing the system prior to installation just to verify that I have adequate stroke and clutch disengagement. McLeod also recommends a 6:1 pedal ratio. I haven’t measured the Pantera clutch pedal but regardless of the leverage ratio of the pedal it will just take the necessary foot pressure to actuate the clutch.

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CNC .75” Bore Master Cylinder

Ready To Be Reunited For Bench Testing

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mc leod 1400 series hydraulic throw out bearing zf

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