Johnson loader info

[jajiu 55]

With a little nice weather around, I'm doing some work on my  and I just put new tires on the rear and just noticed a small leak from the hydraulic tank and would like to find some info on this.  It is a manual dump and the  is a 1977.  I can find no markings on the loader, but was told when I bought the tractor that it is a Johnson.  Any help would be great.  Thanks.

[953 nut 55,837]

Looks a lot like my Johnson Workhorse FEL.