my diff is leaking oil slowly out were the drive shaft connects ..any ideas what would cause this

Remove your drive shaft and the big nut and flange behind it on the diff. There is a seal there.

do i need to replace the seal or just tighten the bolt?
if so what is the actual name for the seal?
thanks

Yes you need a new seal. It is the driveshaft seal! Either the front or the rear..
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Behind that big nut on the diff is whats called a crush sleeve. If you remove the nut and replace the seal do not overtighten the nut, it will affect your clearances on the pinion gear.

What kind of vehicle do you have? We could probably help you more if you gave some details of your vehicle.

Forums, internet, don't you love it...

Guy writes in, has no idea what he it looking at (no offense)asks for advice and then the poor advice stream begins, changing a pinion seal without at least some know how is asking for a repeat of the leak at best, killing good operating set of gears or complete lock up and flying into a ditch (or on coming traffic with a schoolbus full of kids) at worst.

Take it to a shop, get it done correctly.

NOT a jiffy lube or other gas station idiot, but rather a shop that knows that axle assy inside and out.

80CJ at least is asking for more info.

The crush sleeve is not right behind the seal, rather between the inner and out bearings. Getting that nut off with hand tools can be done, but getting it apart is not even close to as important as getting back together correctly.

SD

Supe You are assuming he will install a NEW crush sleeve.. We are assuming he will simply pull the seal and install a new one without getting into the crush sleeve.
New seals are installed every day around the country without messing with the sleeve.
Sure if he takes it to a pro he will pay for a new sleeve and prolly new bearings also... but doing the job under his OAK simply requires a seal and nothing else.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Jim, dude, have you ever overtightened a pinion nut and smoked an axle?
I've certainly seen what happen when the under-qualified do jobs they should have let a pro do.

If it comes to being on the roads and highways with DIY's running questionably repaired rigs or rigs having been repaired properly/professionaly...If you feel there is a contest here... chime in. Otherwise read what is in front of you, this particular fellow clearly has no clue as to what to even call the part that is bad, much less install it correctly.

There are MANY qualified DIYers out there, I'm happy for them, that is how I got started in this industy.
Even today, I won't work on my diesel engine myself, because I'm underqualified to do it. I change the oil and use only oe parts.

SD

No I have not ever overtightned an axle nut..
I respect your oipnion Supe. However most folks that don't know what they are doing would find it hard to overtighten an axle nut without propper tools. Usually with meager tools it would he hard indeed to get 150lbs on that nut.
To me it is a simple matter of a $10 seal versus a $600 pro install of new bearings and a complete reseting of the R$P.
I have been riding for 2 years on a rear end that I replaced the seal on the pinion. In fact I drove it this morning in the rain.
Although WE here in the states depend on professional mechanics to do menial work...around the world replacing that seal is a common practice.. If all it needs is a seal... for gods sake just replace the seal.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />