the charge pump feeds the hst with pressurized fluid. The hst needs it, for a lot of reasons but the main reason is to eliminate air pockets in the fluid-which increases the efficiency of the hst dramatically. They hate air in the fluid.
With that said on a B2400/B1700 the charge pump sits on the front of the transmission. You can't get to it without splitting the tractor, e.g., removing the transmission from the main frame. Pretty involved job. Well it ain't that bad but it's certainly more work than I want to do. B21's are the same way but they have more stuff in the way. A lot more.
if the charge pump is failed, there's very good possibility that there is other transmission damage. You won't know until you either get more information, OR the transmission is removed/disassembled for inspection. If in fact the hst is damaged along with the charge pump, it can get really expensive to fix. If it's just leaking, it could be a simple o-ring on the inlet pipe at the bottom which is a $5.00 part and takes about an hour to replace, OR it could be a totally failed charge pump and we have an idea where that could end up. You won't know until you can look at the tractor and isolate the source of any leaks. Hope it's at the pipe on the bottom of the pump case that would be real easy. Might have to replace the pipe and o-ring and be back in business.
-this is all assuming it's a b1700 or b2400. Or perhaps a B2320 or B2620 but BX series are completely different tractors. I am referring only to the b1700/2400/2320/2620 in the above comments.
