I used an Edelmann kit from my favorite parts house and followed the instructions in the '78 FSM. I came across two glaring errors in the manual:
In three places it says that there are 24 recirculating balls, 12 silver and 12 black, (0.280" diameter and 0.279" diameter respectively, not mentioned in the book) In fact there were only 11 of each. I called a rebuilder who told me that while 24 would fit, they had found out that they were too tight and sometimes caused rough operation so they assembled the boxes with 22, or some other number of balls depending the particular mix of components.
My advice is to be very, very careful to not drop any when taking the box apart and immediately count the balls. There should be an even number.
The written instructions and a photograph say that the oil return port will be completely exposed. If any part of it is covered by the valve body there has been a mistake in assembling or installing the stub shaft/valve body/worm shaft assembly. Not true. I took the thing apart and put it back together a half dozen times and every time there was about a quarter of the hole diameter covered by the spool valve. Again I called the rebuilder who said that was common, again depending on which component parts were used.
My advice: After removing the stub shaft adjuster plug, look in at the return oil port and note its relation to the spool valve. When putting it back together, be very careful assembling it and then make sure that the valve goes back to its original position. If the thrust bearing is put in backwards it will only displace the spool valve a tiny amount, so this requires great care.
One other discrepancy is that the FSM says that the Teflon seal rings, similar in function to piston rings, will be loose on the piston and valve body when they're first installed, but will tighten from contact with hot hydraulic oil. That caused trouble when doing the adjustments. The torque required to turn the stub shaft should be 4 to 10 inch pounds with the pitman shaft adjustment completely backed off. On the fresh rebuild it was 30 inch pounds. Since I couldn't do the proper procedure, I set the adjuster plug per the instructions, and set the pitman adjustment by turning the screw down snug and then backing it off about a quarter turn. I will remove the box in the spring when the snow plow is off and adjust it properly.
After the box was installed it developed a tiny leak from under the pitman shaft adjusting screw locknut. The manual says to cure that leak by replacing the nut, but it was new with the kit. I fixed it by turning a small recess in the bottom of the nut and putting an O-ring under it.
The job is not easy. There are a lot of parts, some very precisely machined and match-fitted. Everything must be exceptionally clean. Some things will fit an alternate way but not work properly. I had to make an arbor tool on the lathe (.610 diameter nylon). Were I to do it again I'd also make a tool to install the pitman shaft seals. If not for the errors in the manual it would probably be a three or four hour job, but I spent a couple of days on it.
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In three places it says that there are 24 recirculating balls, 12 silver and 12 black, (0.280" diameter and 0.279" diameter respectively, not mentioned in the book) In fact there were only 11 of each. I called a rebuilder who told me that while 24 would fit, they had found out that they were too tight and sometimes caused rough operation so they assembled the boxes with 22, or some other number of balls depending the particular mix of components.
My advice is to be very, very careful to not drop any when taking the box apart and immediately count the balls. There should be an even number.
The written instructions and a photograph say that the oil return port will be completely exposed. If any part of it is covered by the valve body there has been a mistake in assembling or installing the stub shaft/valve body/worm shaft assembly. Not true. I took the thing apart and put it back together a half dozen times and every time there was about a quarter of the hole diameter covered by the spool valve. Again I called the rebuilder who said that was common, again depending on which component parts were used.
My advice: After removing the stub shaft adjuster plug, look in at the return oil port and note its relation to the spool valve. When putting it back together, be very careful assembling it and then make sure that the valve goes back to its original position. If the thrust bearing is put in backwards it will only displace the spool valve a tiny amount, so this requires great care.
One other discrepancy is that the FSM says that the Teflon seal rings, similar in function to piston rings, will be loose on the piston and valve body when they're first installed, but will tighten from contact with hot hydraulic oil. That caused trouble when doing the adjustments. The torque required to turn the stub shaft should be 4 to 10 inch pounds with the pitman shaft adjustment completely backed off. On the fresh rebuild it was 30 inch pounds. Since I couldn't do the proper procedure, I set the adjuster plug per the instructions, and set the pitman adjustment by turning the screw down snug and then backing it off about a quarter turn. I will remove the box in the spring when the snow plow is off and adjust it properly.
After the box was installed it developed a tiny leak from under the pitman shaft adjusting screw locknut. The manual says to cure that leak by replacing the nut, but it was new with the kit. I fixed it by turning a small recess in the bottom of the nut and putting an O-ring under it.
The job is not easy. There are a lot of parts, some very precisely machined and match-fitted. Everything must be exceptionally clean. Some things will fit an alternate way but not work properly. I had to make an arbor tool on the lathe (.610 diameter nylon). Were I to do it again I'd also make a tool to install the pitman shaft seals. If not for the errors in the manual it would probably be a three or four hour job, but I spent a couple of days on it.
