L275 problems.....

Hey guys,
Its been quite awhile since I've been on here (been busy trying to build an addition). I have a L275 4 wheel drive tractor that I'd like to get back to working on.
The first issue was that the 4wd was not working. I have since found out that right side mechanics behind the wheel are shot. (The seal leaked on the PO and it was never replaced and......) SO, does anyone know where to get parts or what other tractor they may have been used on?
The second issue is the hydraulics on the loader. It lifts slowly and can't lift much. I have replaced the pump, checked the pressures at the port under the seat (they meet spec). Now what? Following procedure in the manual, there is a little tab on the 3pt lever that you move out of the way to do the pressure test. If I raise the bucket with this tab moved, the bucket flies up but won't go down. So what does that little bit of extra throw on the level do?

Thanks,
Josh

Thanks for the reply. On the 4wd problem, I downloaded a copy of the parts manual page from Messicks, so I know what parts I need. However, they (and other suppliers) don't stock most of them and Wengers (the salvage company) didn't have anything either last time I checked. I guess parts for a tractor pushing thirty years old are getting harder to find.

For problem two (hydraulics) - as far as I can tell there are no screens aside from the blue filter. I did read earlier today on a different post about a vent hole, so I'm gonna look for that next.

Any suggestions are welcome.

(as far as pics, I'm on dial-up which seem to be the next best thing to carrier pigeon in this high speed world so that may take awhile )