Leak from rear axle flange seal?

As I have said elsewhere, dead easy to replace.

What sort of hood latch do you have? The OE is a double latch, and should not even effect the pins. The 69 mach1 pin set is still available, if you have to have pins, that's what I'd use.

The pinion flange seal on the front of the differential is easy to replace. Takes about an hour if you have a lift. Remove the drive shaft. Use a drift pin punch to immobilize the pinion flange (or a big pipe wrench) and remove the pinion flange nut. Mark the pinion flange and pinion shaft with paint mark for alignment- probably unecessary, but I'm cautious. Remove the pinion flange. This may require a puller, so have one handy before you start. Lever the old seal out of the housing. Install the new seal. Install the pinion flange. Install a NEW pinion flange nut, and torque to 125 ft-lbs. (These nuts are not hard to get, because since the 50's, the 7", 8", 9" 7.5", and 8.8" all used this same nut.) Install the drive shaft. Top off oil level. The whole job should cost you about $20.

Before 100 people start with the "crush collar blah blah blah…" this is a well-documented and time tested method for replacing the pinion seal. The crush requires 175 ft-lbs to compress, so all this does is seat the new nut exactly where the old one was. This is NOT useful for axle rebuilds, but is excellent for pinion seal replacement.

2+2GT said:

The pinion flange seal on the front of the differential is easy to replace. Takes about an hour if you have a lift. Remove the drive shaft. Use a drift pin punch to immobilize the pinion flange (or a big pipe wrench) and remove the pinion flange nut. Mark the pinion flange and pinion shaft with paint mark for alignment- probably unecessary, but I'm cautious. Remove the pinion flange. This may require a puller, so have one handy before you start. Lever the old seal out of the housing. Install the new seal. Install the pinion flange. Install a NEW pinion flange nut, and torque to 125 ft-lbs. (These nuts are not hard to get, because since the 50's, the 7", 8", 9" 7.5", and 8.8" all used this same nut.) Install the drive shaft. Top off oil level. The whole job should cost you about $20.

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2+2GT has given a great explanation on how to do this job. Having just done this last weekend I have a couple other things to add.

When you get that seal out gear oil will come out so have a bucket handy. To minimize the amount lost you can lift the front of the vehicle up higher than the rear but you will still get some spillage.

To make the process easier to torque the pinion nut I use a 2-3 foot length of 1 inch box tube. I drilled 2 holes in it to line up with one side of flange where the u-joint straps go. Then I slide it between the passenger side spring and framerail and put 2 bolts into the holes on the flange for the u joint strap. Now you can torque away without having to worry about the pinion spinning.

If the axle seal is leaking, there's a better than average chance the axle bearings are going south too. Park it and replace both axle bearings and seals. If these bearings go while on the road, it's not a pretty sight.