How difficult?

[roncampbell]

On my 99 Ranger the input shaft to the front differential is leaking how hard a job is it to replace? My expirience level is clutches ,timing chains and head gaskets.

 

[4x4junkie]

It's not real hard, but there's tons of room for error on reassembly.
You will need to precisely mark the pinion nut and shaft so you can put the nut back on EXACTLY like it was, otherwise the pinion bearings can get damaged if it's tightened too far, gears damaged if not tightened enough. This will also only work if replacing JUST the seal. If anything else is replaced (bearings, etc.), the bearing preload will need to be rechecked as well.

You must use Loctite on the pinion nut upon reassembly, otherwise it may loosen.