My 963 recently started leaking a little oil from the bell housing breather. First thought was that I over filled the pump drive. Thats not the case the pump drive will maintain full and transmission will loose oil. started pouring out today, checked pump drive level and its still full transmission is bellow the add mark. any thoughts? other than that machine operates as it should breaks are laking a little. cant find anything in my books on it. Its definitely the bell housing breather and not the breather on the pump drive fill neck. machine is a 21z54xx 8500hrs
Just noticed there are two pumps that drive off the bell housing and I'm suspecting that one is leaking into the bell housing.
Well I'm stumped, checked the charge pump its not leaking and the main pump isn't tied into the transmission from what I gather out of my book. Looks like to me the transmission is leaking into the bell housing but if that was the case wouldn't the pump drive be over full?
The pump drive input gear has an open bore with a spline all the way through. One side accepts the drive shaft from the flywheel, the other side has a shaft that runs through the transmission case to drive the charge pump. The shaft from the flywheel has an O ring on it to seal in the tranny oil and it is probably this O ring that has failed. Later machines have two O rings for better reliability. You'll have to pull the engine or transmission to fix it. Engine is easier. You might want to think about replacing the lip seal between the pump drive and bellhousing while you are at it.
Just got it back together this afternoon, while I had the engine out fixed a few oil leaks and needed an exhaust manifold gasket which turned into broken studs in the head which lead to head at machine shop that turned into getting a head job and a new exhaust manifold. Replaced lip seal and the two O rings on the drive coupler along with the O ring inside the drive coupler. When I removed the transmission cap to top off the oil I noticed it had pressure on it. Never really noticed that before is that normal? Not a crazy amount could just hear a little air while unscrewing the cap.
I think I may be having the same problem. Did replacing lip seal and the two O rings on the drive coupler along with the O ring inside the drive coupler fix your problem? My seals and o rings were replaced and I still have the leak. They may have damaged them during reassembly but I was wondering if there might not be another issue. Thank you.