so today i put a thrush mufler on my d, and when i was under my truck i noticed oil on my undercarrage and on my gas tank. i looked at my yoke and i saw that it was wet. i checked to make sure i didnt have any slop on it and there wasnt. so i pulled the plug out of rear end and checked my gear oil and it was slightly below the plug hole. so filled it. is the oil coming out of my yoke due to a bad seal? if so is a serious problem? or will i just have to check my oil level once a month and top it off?

 

Most likely a bad seal... personally i would replace it soon.. a bad seal is way much cheaper to replace than a bad rear end after all the fluid has leaked out.

 

I would keep an eye on the rearend oil an change the seal in it as soon as I could,

 

Pretty easy to replace. remove the u-joint and yoke. Get a heel bar in there to pop out the old seal and drive the new seal in evenly. Clean the yoke's seal mating surface up with some fine grit crokus cloth if there is wear in the yoke that cannot be taken off with minimal sanding you will have to replace the yoke.