Check fluid pressures. Real easy. Cooler line fitting for low side. Should be steady at 40psi. F&R ports are onto of valve body. 1/8 NPT fittings required and a psi gauge of 300psi rating. Clutch pack pressures. Need to be steady and above 120 psi within 3 to 5 seconds of selected direction

You can just crank engine over to see if you have a good pump with a cooler line off. If flow then pressures. If one is low. Possible snap ring or pack blown apart. Either way no pressure it has to come out.