The pinion seal on my 3.63 diff started oozing fluid. I'm not wanting to tackle replacing this on my own. I'm having a reputable shop do the work. They want me to get the parts. My question is, do I need to get anything other than the seal? The original crush washer stays intact? The 3.63 diff takes the same seal as a 3.9, doesn't it?

 

same housing, same seal.

as long as they check the rotational torque with an inch lb torque wrench before they disassemble they can put it back and reset it to the same value... Otherwise need to change the crush sleeve and reset it. Easy enough to check rotational torque though and get back within 1-2 inch lbs which will be good enough...

You could also have them go to a pinion spacer in place of the crush sleeve which provides a little better pinion support.