Rear differential leak

[genx75spider]

I have a 74 spider and the rear differential leaks from where it attaches to the drive shaft. I looked it up in the workshop manual and it is probably a bad oil seal. My question is, how hard is it to change this seal and if I try to take it off will I mess up the pinion alignment? Does the seal just pop out after you take the "u"joint sleeve off? Thank you for any help.

[redcars]

If it is leaking where the driveshaft fastens then it is not the seal ,but it is leaking around the splines and then by the nut. If the seal is leaking it will be leaking right where the flange comes out of the housing. For the spline leak take the nut off of the pinion shaft, pull the flange off clean everything up nice, now for this part it has ben a while so I am a little fuzzy. Put the flange back on and put RTV where the flange and nut meet up some thread sealer on the threads. Put the nut on and torque it down. This stopped my leak when replacing the seal did not. If in fact the seal is leaking then when the flange is out remove the seal and do everything else the same.

[genx75spider]

Thank you very much for the help, I really appreciate it.

[majicwrench]

A close look will usually tell ya if it is leaking past the splines or the seal. How bad is it leaking?? You may want to leave sleeping dogs lie. You have to get that pinion nut pretty dang tight.
Keith

[genx75spider]

Its hard to say how much it leaks but when I parked it last time it the puddle was about 8 inches wide and about 2 foot long. When I took it out the other day I parked it at a restaurant and it leaked only a few drips. It seems that when it cools down it leaks the most. I have a buddy who is a fiat nut as well. He said that I should just leave it alone because he had one worked on by a mechanic many years ago and he said it was a pain to repair. What do you think?

[majicwrench]

If it leaves a puddle 8inches by 2feet you HAVE to fix it before it runs dry and ruins your rear end. If it just leaves a drip or two it's your call.
Tis an easy repair for a decent mechanic, in a backyard situation the pinion nut will give you issues.
Keith