Hydraulic Clutch
When I first started looking at the bellhousing that came out of the Chevy bread van with the Cummins, it looked like it would be easy to set up the clutch linkage. The Chevy setup had a z-bar on the left side of the bellhousing that required one inch of push from the linkage rod in order to fully actuate the clutch. The bellcrank on the clutch pedal shaft pushed a linkage rod one inch forward when the pedal was depressed. I figured that all I would have to do was shorten the z-bar a little to fit the gap between the bellhousing and the left frame rail on the Dodge (which was smaller than the gap when the engine was installed in the donor Chevy) and then install a turnbuckle for adjustment between the pieces of linkage rod I already had.
Things are never as easy as they look.
It turns out that between the motor mounts, brake lines, and other assorted hardware on the left frame rail that it was virtually impossible to fit the z-bar into place once the engine had been set into the frame. It also turned out that connecting the original linkage rod to the one on the clutch pedal was harder than I thought it should be since the diameters of the rods where different.
After talking to a couple of friends who spend a lot of time working on stock cars or going off road in their jeeps, it seemed like a good solution to the problem would be to use a hydraulic clutch setup utilizing a master cylinder with a remote reservoir coupled with a hydraulic throw out bearing. The idea was that I would eliminate the problems associated with fitting the z-bar into the truck and with the linkage rod alignment by going hydraulic. I decided to use a remote reservoir master cylinder so I could mount the MC on the frame rail near the bellcrank on the clutch pedal shaft while having the reservoir mounted high on the firewall in order to prevent air from accumulating at the slave cylinder and to provide easier access for fluid level checks. I would have a cleaner installation using a hydraulic throw out bearing instead of the more common externally mounted slave cylinder since the slave cylinder would be incorporated into the throw out bearing and would be totally inside the bellhousing. The downside to the setup would be that the transmission would have to be pulled any time I needed to service the slave cylinder...
After looking at several of the components listed in some of the stock car product catalogs, I decided to use a Tilton remote reservoir master cylinder and a Howe hydraulic throw out bearing combination from Performance Bodies.
When I called and talked to the folks at Performance Bodies, they informed me that the proper master cylinder to use with the Howe hydraulic throw out bearing designed for use with a GM/Chevy stock clutches the unit with a 7/8" diameter. They where a little leery about my plans to use the Howe unit for use with "stock" clutches and Saginaw, T-10, and Muncie transmissions (Part number 82870) since I told them that it would be going onto an Advance Adapters Ranger Overdrive that was mimicking a SM465 transmission and they had no experience using the unit in this application.
Once I received the throw out bearing, I pulled the transmission and bellhousing combination back out of the truck and removed all traces of the mechanical clutch setup from the bellhousing. I then removed the bolt at the five o'clock position on the bearing retainer of the Ranger OD (as you face the unit) and replaced it with one of the one ended studs that is provided with the throw out bearing. The stud is threaded on the end that goes into the transmission, but is smooth on the other end where a finger on the release bearing rides. This finger prevents the hydraulic throw out bearing from rotating (which would be disastrous to the hydraulic lines attached to it...).
I then removed the bleed fitting and line adapter from the realize bearing and replaced them with a pair of line adapters that I had purchased locally. I attached a pair of braided brake lines to each of these fittings and attached the bleed screw to the one attached to the top fitting on the bearing.
I then slipped the throw out bearing over the bearing retainer on the transmission and determined that I did not need any of the shims provided to properly position the unit in relation to the clutch fingers. I threaded the hydraulic lines through the hole in the bellhousing vacated by the clutch arm and replaced the bellhousing and transmission combination back into the truck with the help of a couple of friends.
I then fabricated a mounting bracket for the master cylinder. The bracket is L shaped and is formed out of a piece steel plate and a strip of angle iron welded together and bolted to the frame rail. It is located on opposite side of the rail as the brake master cylinder and is almost in line with that unit.
The bracket is held on using the same bolts that hold the front running board bracket in place. I did replace the bolts with ones 1/4 or a 1/2" longer. The angle iron is a 1"x1.5"x1/8" piece that is about 3.5" tall (just fits inside the frame rail). The plate is 3/16" thick and is 3.5" tall, 4.5" wide with the width overlapping the angle iron. The plate is aligned 0.25" up from the top edge of the bottom frame flange.
After welding the plate to the angle iron, I fitted it to the frame and marked location for holes to mount the bracket to the frame and to fit the master cylinder into the plate. I drilled a pair of holes in the angle for the frame mount, a pair for the master cylinder mounting bolts, and then used a hole saw to cut a large hole in the plate for the body of the master cylinder to pass through.
I then mounted the reservoir (using the smaller of the two supplied, the big one gets used with brake setups where you need a lot of fluid to make up for pad wear) onto the bracket that used to hold the voltage regulator. I drilled a pair of holes in the front face of the bracket and used a hole saw to put a hole in the base big enough for the reservoir outlet to clear with ease. I cut the rubber hose supplied with the master cylinder into four equal length pieces (using two and reserving the other two for future use) and connect one of the pieces to the outlet of the reservoir. I then ran a section of steel brake line down the firewall connecting the top of the line to the rubber line on the reservoir and pointing the bottom section towards the place where I was going to mount the master cylinder.
I then put a piece of rubber line onto the inlet cap nipple on the master cylinder and bolted it and its bracket to the frame. I then connected the rubber line to the metal line from the reservoir.
I took the bellcrank off of the clutch pedal shaft. I took a drill and enlarged and rounded out the hole that the pin attaching the push rod attached to since it had been elongated with years of use. I then welded a clevis pin into the hole. I used a die grinder to cut a relief notch in the clutch pedal shaft through the center of the key just deep enough for the bolt through the bellcrank to fit when the bellcrank was reinstalled on the shaft upside down to its previous position. When installed, the opening in the casting fits nicely over the remains of the key to prevent rotation, and the bolt still tightens the unit enough to keep it from coming off the shaft. It then place the clutch return spring clip over the clevis pin on the bellcrank and attached the original spring. I hooked the other end of the spring to a piece of exhaust hanger strop that I had cut off from the hanger when installing the muffler. One hole in the strap was in the correct location for the spring when the other end is attached to the bottom of the frame using the rear one of the bolts that hold the rubber spring bumper in place.
I then attached a heim joint to the end of the master cylinder push rod and went to attach it to the clevis pin on the pedal rod bellcrank. I then discovered that I had mismeasured and that I was short one inch of making a connection. I then went back to my local stock car parts dealer and picked up a rod extension and inserted it between the pushrod on the master cylinder and the heim joint.
I then bent a piece of steel brake line into an elongated u shape and connected it to the outlet hole on the master cylinder and connected the remaining braided line from the throw out bearing to it.
With the help of a vacuum bleeder lent to me by a friend, I filled the unit with brake fluid. I then checked operation of the clutch and found out that I needed to remove the pedal travel limit clip from the floorboard. Once done, I had great pedal action and feel.
I should have put a 1" thick spacer between the plate and the MC face to move the
MC forward 1". I had to extend the pushrod on the MC in order to get the clevis
pin on the clutch to mate to the heim joint and it would have been better to have a
shorter push rod assembly with less fittings. I measured the thing a dozen times,
and I still got it wrong when I put it all together. An alternate solution would be
to put the spacer between the angle iron and the plate...
Parts Used:
Stock Chevy Hydraulic Throw-out Bearing Part# 82870.............. $149.95
Replacement O-ring Kit Part# 82871......... $4.95
“This hydraulic throw-out bearing eliminates the need for a slave cylinder or
mechanical linkage. Simply install by replacing one bolt from the front of the
transmission with a stud that has a smooth extended end that a finger on the TO bearing
rides on to prevent rotation of the unit, and slide the bearing over the bearing retainer.
Conical shims are provided to properly fit the bearing to zero clearance. Made to work
with Saginaw, T-10 and Muncie Transmissions.”
Note: Works on SM465 (actually an Advance Adapters RangerIII OD set up to look like the
SM465 that came with my Cummins...) with no shimming. I did need to get a few fittings and
a pair of flex lines to go from TO bearing to MC and to
bleed screw as they do not supply any of these with the unit. I am using the bread
van bellhousing that came between the Cummins and the SM465 that I removed from an
Entenman's Bakery truck. The bellhousing was setup for a mechanical linkage on the
left side.
Tilton 7/8" Universal Master Cylinder Part# 875U.complete with fittings $59.95
"This Master Cylinder kit that Tilton manufactures is great for fast and easy fluid
level checks! The cylinder has an aluminum design that comes with large(10.7 oz) and small
(4.0 oz.) reservoirs with screw on caps. Complete kit with fittings."
Note: You need to use a different (longer) rubber line than the one supplied with the
master cylinder that is brake fluid compatible or cut the line into a couple of pieces and
use a length of steel brake line bent to conform to the firewall contours to extend the
line provided. You have no pressure on this segment (gravity feed from reservoir to master
cylinder, so you can use four hose clamps to tighten theconnections. I prefer hose clamps
to the wire ties provided.
Second note: The numbers pulled off the pressure plate and clutch disc are:
Pressure plate 116-1080, bbc-1900 Borg and Beck. Clutch disc 167388, 260999 2238
Valeo.
Pictures of the setup can be seen on photo
page eight.