My 680C has developed a slipping problem when it is in forward gear only. When I shift into forward the shuttle is slipping from fully engaged which is normal to almost into neutral. Notice I said almost neutral. It does this at constant intervals. I can better describe it as chugging effect. It will do it with any of the four gears in the four speed transmission. It is most severe when the I first start using it with the machine at air temperature. The severity decreases to almost unnoticeable at operating temperature. The oil in the shuttle and the convertor were completely changed 300 hours ago. The oil filter (screen) was spotless at that time. I changed the oil in the shuttle last week and it was clean and again the screen is spotless. I couldn't change the convertor oil without removing the shuttle. Yesterday the machine was at operating temperature and I locked the brakes, put the gear box in fourth gear forward and with a wide open throttle I could barely feel the shuttle slipping symptom. It did it at constant unchanging short intervals. The convertor seems to be in good condition because the engine was under a heavy load. The convertor temperature barely moved up. I only did this long enough to determine that it was doing this with a heavily loaded drive line. Would anyone have an idea as to what is causing this ?
Late this afternoon I couldn't go up a 4/1 slope in forward. It didn't matter what gear the four sped transmission was in. I sat at the bottom of the slope and the shuttle went in and out of gear at a continuous rate. I had to turn around and back up the slope.
Well I finally found the problem. The previous owner and myself have been checking the shuttle oil level with the machine shut off and at operating temperature. We always kept it on the full mark or about a quart overfull. The machine always seemed to work OK until now. But as I thought back about running it through the years it always jerked in and out of gear on a 4/1 slope or steeper going up it. I never before looked in the shop manual as to what the conditions need be to check the oil level in the shuttle. What an eye opener ! --- The machine has to be at operating temperature , brakes locked and the transmission in fourth gear and the shuttle engaged in forward, engine idling. Well ol dumb a## thought it was always full the way I was checking in the past. It was a little over a gallon low when I checked it the way service manual instructed. It takes 3 gallons to refill a dry system. So all along, 1/3 of the required amount was missing. It is no longer jerking in and out of gear and I can go up that 4/1 slope in THIRD gear without a problem. I always said you can get by without a service manual but this one of those situations where I would have never figured out the problem without the manual.