Rear diff leak at driveshaft - how serious?

My truck (2001 Dakota 4x4) is leaking fluid out the rear diff, at the point the drive shaft goes in. It's certainly concerning, as it's bad enough it is wet underneath, and fluid is obvious flowing back along the
full length of the differential. However, it is not dripping, no fluid on the pavement even after a full day of being parked.
There are no new weird noises or sounds - there's been a brushing noise for a while from somewhere, that I can only hear with the passenger side window down, and something like a curb to bounce the sound off of. That's been pretty steady and I'm nearly certain it predates any possible leak. The question is - If I drive it like this for a couple more days, am I courting the whole thing seizing?
I can post pictures if that'll help. I'll at least have to drive it about 20 miles tomorrow, still have to go to work and back, planning on stopping at my mechanic on the way home; had to work late, they were closed when I tried that today.
FWIW, the truck was inspected on the 30th and nobody mentioned this to me. I've no idea how much fluid is supposed to be in that end of the diff... the back seal is fine.
Appreciate any advice, and hope everyone's fine, been very quiet around here lately.
jmc
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You need to have someone replace the pinion shaft seal to stop the leak, and you need to check the gear lube level in the diff. immediately before it is so low that the unit is trashed before the seal is fixed.
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On 8/10/2011 7:17 PM, jmc wrote:

Well, my advice, FWIW, is the following:
1. Immediately check the fluid level. Top off as needed. 2. Try to get it fixed as soon as you can (few weeks should be no problem), it can only get worse!
But, monitor it carefully... Each time you drive, check to see if it is leaking any more than before.
--
I'm never going to grow up.

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Suddenly, without warning, jmc exclaimed (8/10/2011 7:17 PM):

Thanks for the advice... My mechanic said it would be fine to Tuesday. Said if it was a big leak it'd be flung all over the underside of my truck... also figures it's the pinion seal. Well, it's over 10 years old now, I'm not surprised that seals are failing, considering the temperature extremes this truck has endured...
It'll be fixed on Tuesday. I would assume if there was anything wrong within the diff, I'd have noticed something, right? Noise, feel, smell?
Hope all are doing well here.... as I said, been fairly quiet.
jmc
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Jodi,
I may be having a senior moment but didn't you have some major work done on the rear in the past year or two?
I assume being an old dodge rear that it has a crush washer (more like a tube with a bulge in it). If it does make sure that they replace it and properly torque the yoke nut.
beekeep

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Suddenly, without warning, beekeep exclaimed (8/12/2011 12:14 PM):

> Jodi, > > I may be having a senior moment but didn't you have some major work > done on the rear in the past year or two? > > I assume being an old dodge rear that it has a crush washer (more like > a tube with a bulge in it). If it does make sure that they replace it > and properly torque the yoke nut. > > beekeep > >
I think all the work on the truck last spring was on the front end (unless I'm misremembering where the transfer case is). The diff leaked out the back seal a few years ago, but that end's fine.
I figure since most of the front is new, it's about time for the back end to get creaky now. Ah, well. I still like my truck, and it's still cheaper than buying a new one... I've already put more $$ into repairs than it's worth according to Kelly, but it's worth more to me :)
jmc
(Oh, and because this is really cool if totally off topic, for the first time, I sat on my two year old colt Yankee today. He was awesome, didn't bother him at all. Those of you with some knowledge of young horses probably understand how cool that is.)
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