JD 310SG, power shift. Start machine, cycle park brake switch, machine will roll, but when moving shuttle to either forward or reverse it will try to creep but that's it. RPM, gear or otherwise doesn't matter. Trans oil level is good. On occasion, shaking the machine with the outriggers, front bucket or such helps. Once you get it moving, its usually good for a duration. Will replace PB switch just because it is exposed and will used. Doesn't appear to be starving for oil, since when it decides to engage, it is abrupt. There is no ramp up. In the thread below, there is mention of the solenoids. Similar thoughts here? Thanks
Serial number? Does the park brake light go out? The (3) most likely contenders are: 1. Clutch cutout switch on the loader lever. 2.. FNR. Is it sending the necessary signals? 3. Timer relay (under instrument panel). Has that been checked? If all checks out then the Forward Clutch pressure (labeled PF) and Modulation pressure (labeled PM) need to be checked.