I have a Hummer H1 that I'm working on that has the 6.2L diesel and the TH 400 transmission. The tranny won't shift unless you wind out the motor then it'll bang into gear. I took the transmission to a shop to have it looked at but it checked out fine, they told me to replace the modulator valve and cable that runs to the injection pump. I installed a new valve and cable but it still does this, I've tried adjusting the slack to get line pressure but still have no luck. Could this be a faulty transmission pump or torque converter? Any help would be greatly appreciated, thanks