So I have noticed thjat my differential is leaking from the plug and around the seals, I looked in my service manual and and overhaul is all they cover on this subject. Has anyone done this repair and can explain iot to me a bit? Also where can I find replacments for the plugs in the differential. Thanks in advance for any help. Oh and by the way my car is a 58 Yeoman with all stock 283. Thanks

I don' tunderstand what "plugs" you are refering to. The is a filler plug on the rear and it uses a gasket. There in no rear cover on a 1958. The studs/nuts that retain the carrier to the axle housing are at the front ( 10 of them) and copper washers are used under the nuts to prevent seepage. If the leak is between the axle housing and front carrier, the gasket can be replaced but removing the axle shafts is necessary. This is often a problem as the outter axle bearing often rust tight into the axle housing and a very large slide hammer puller plus some heat is required for removal. New axle seals (they fit into the wheel bearings) should be used. The other common point of leakage is the pinion seal. It fits into the front of the housing where the pinion shaft passes thru.
If I owned a 1958-64 I would also consider repacking/replacing the three U joints and the center drive shaft bearing. These were problem points on these cars.

i see the plug on the back you are refering to, I thought I had seen one on the bottom too, It appearts the majority of the laek is from the plug but aprooximatly the bottom half of the diff has fluid on it too. As far as what to repair/replace I had figured that if I was in the unit to replace one seall I would go ahead and knock it all out. I will look more closely at my shop manual and see if I have any more questions. Thanks for the help

I forgot about the plug on the bottom. Was used in 1957-58 only. Due to the noisy rears ends in 1955-56 they made several improvements in 1957. One was to use a special break-in oil that was to be changed at 1000 miles. They added the plug to encourage the change. (was removed in 1959 and necessary to suck the oil out. The drain plug and gasket are the same as the oil pan drain plug. Often a drip of oil can be seen hanging from the plug. In most cases it something above thats leaking ( usually pinion seal) and the head of the plug is the low point for for the gear oil to drip from. My '57 usually has a drop hanging from the plug, the pinion seal has a slight leak, fluid level never goes down, and its at the end of my "to do" list. If the car was used every day it probably wouldn't be noticed but the various oil leaks look worse when the vehicle sits unused for longer periods of time. When used on a daily bases the drips get blown/washed away and are seldom noticed.