I have worked on Tractors in my life but have nt had to deal with forklifts other than driving them, I bought a Clark C300-40 at auction it starts and runs great and owner said it had the brakes redone which are working good. The hydraulics all work properly.
The quirk that it has it is when shifting into forward or reverse it does not move right away. You have to turn the steering wheel from left to right and then it seems you hit the sweetspot and it will start moving forward or reverse and then goes fine. The steering seems to be running on a separate hydraulics with the front forks.
Now upon remove the floor plate and exposing the transmission, the linkage from the shifter connects to a small shaft. That connection and shaft seems loose and has a lot of play or wear moving between F and R when. Have to hold the shifter forward to engage the starter due to safety switch on the loose shaft on the transmission top plate. Also there is a another valve that is actuated when brakes are pushed. I am trying to find a service manual to find out the mysteries of all the valves and actuators on the tranny and to increase my knowledge on this machine. But thought i would throw it out here to get direction on a fix or remedy