The valves can be resealed without taking the blocks off the tractor. You need to clean everything around the valves very clean. If you can not do that do not even try to take them apart. Do one valve at a time. Do not mix parts. The spools are a select fit with it's valve body. To replace the o-rings you need to slide the spool out the back. Begin by disconnecting the front of the spool from the lever. Next, unscrew the pipe with the cap and plug still on the end, With the spool and pipe assembly removed from the valve body, unscrew the big plug from the pipe. Clamp the front end of the spool in a vice with the end with the adjusting screw facing up. Clamp only to flat side on the front of the spool. Any damage to the machined surfaces of the spool can destroy the valve assembly. Remove the adjusting screw, spring, ball seat and four steel balls. Remove the outer pipe and detent sleeve. Using a 1/2 x 20 (NF) cap screw with nut, install it where you removed the adjustment screw. Tighten the nut on the top of the spool and use the bolt to remove the remaining part of the detent assembly. The o-ring that is leaking is inside this piece. The pin an o-ring are replaced as an assembly. Replace the other o-rings. There is one located the the front of the block that can be replaced with the spool removed. Assemble everything in the reverse order you used to take them apart. Adjust the detent screw so that the detents will hold the valve on causing the hydraulic relief valve to open. Then back the screw out 1/4 turn at a time until the detents allow the valve to return to center when maximum hydraulic pressure is achieved. You can set them lower if you want, just make sure they recenter themselves rather than stay on high pressure,
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