I have an L2900 GST 4WD with 600 hours on it. At first, it intermittantly wouldn't move in 4th or 8th. Now it won't move at all. Feels like it's in neutral regardless of shuttle lever or shift lever position. Clutch feels normal and rear pto acts as expected with clutch operation. Hydraulic fluid is clean and at proper level. Dealer thinks it could be the main clutch, but I'm skeptical. Any ideas?