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if i remember in the pan of the overdrive unit there's a little oil filter like in auto trans ,change the fluid and replace the filter.
edit here the filter from Ecklers
The OD filter is the same one that was used in the Ford FMX auto trans. That was installed in early 70's Merc Cougars, some Ford Fairlanes, some Mustangs and even a few versions of the F-150
There's no need to buy the catalog filters at the huge prices. Filters can be had for under $8 bucks and you can use a good black RTV sealant instead of a cork gasket. Here's some filter p/n's
CarQuest 85926
AC Delco TF-184
FRAM FT1024
NAPA ATP14717
(these filters don't come with the rubber grommet, so just move it from the old filter to the new one!)
When you drop the pan, make sure the mating surfaces are completely clean of any old gasket material or sealant. Make sure the pan rails are straight. Run a 1/8" bead of RTV around the pan and the bolt holes. Carefully tighten all the bolts evenly so that the sealant just pushes out.
There has been lots of discussion over the years about what to use for OD fluid. The consensus has been to use DexIII fluid but not synthetic.
It might be a good idea to use low air pressure to blow out the fluid lines to the radiator. Disconnect both lines at the OD and blow the old fluid out. Once that's don and everything is done, raise the rear end and rotate a rear wheel by hand for a couple minutes. This causes the OD pump to circulate fresh fluid thru the lines. Then top off the OD unit.
The OD filter is the same one that was used in the Ford FMX auto trans. That was installed in early 70's Merc Cougars, some Ford Fairlanes, some Mustangs and even a few versions of the F-150
There's no need to buy the catalog filters at the huge prices. Filters can be had for under $8 bucks and you can use a good black RTV sealant instead of a cork gasket. Here's some filter p/n's
CarQuest 85926
AC Delco TF-184
FRAM FT1024
NAPA ATP14717
(these filters don't come with the rubber grommet, so just move it from the old filter to the new one!)
When you drop the pan, make sure the mating surfaces are completely clean of any old gasket material or sealant. Make sure the pan rails are straight. Run a 1/8" bead of RTV around the pan and the bolt holes. Carefully tighten all the bolts evenly so that the sealant just pushes out.
There has been lots of discussion over the years about what to use for OD fluid. The consensus has been to use DexIII fluid but not synthetic.
It might be a good idea to use low air pressure to blow out the fluid lines to the radiator. Disconnect both lines at the OD and blow the old fluid out. Once that's don and everything is done, raise the rear end and rotate a rear wheel by hand for a couple minutes. This causes the OD pump to circulate fresh fluid thru the lines. Then top off the OD unit.
Excellent advice. I use a sealer called "The Right Stuff" when I replace the pan. It's a little pricey, but it NEVER leaks.
Excellent advice. I use a sealer called "The Right Stuff" when I replace the pan. It's a little pricey, but it NEVER leaks. 
