I started to bleed my brakes yesterday and noticed there was some sort of oil all over the underside of the bed. It started on the tail end of the gas tank and ended just before the actual axle and went almost side to side. Pretty wide spread. I couldn't see any specific point of leaking, but it's definitely getting slung all around. It's not coming from the vent connection to the diff housing and I can't see any other probable locations. I put a whole bottle of diff oil in(the very expensive 140 syth stuff!) so it was pretty dry. I'm glad I caught it now before it got worse, but I need to figure out what's leaking. My best theory is that it's leaking out the front and getting slung by the u joint as soon as it hits it. Any body got any ideas?

BTW it's a 98 F150 2x4, 181,000, which other than using some oil is a great running truck!

 

could be that front pinion seal. Pull the driveshaft off, it will give ya a better look.

if you do need to replace it, its pretty easy. the trick is getting that pinion nut off. Once its off, its easy to get the seal out, and new one in. When putting that pinion nut back on, make sure to use a torque wrench, and not a impact gun. The gun can destroy the crush sleeve. I think its 90 ft lbs, but would have to double check that, not sure.

 

Good advice, that could be it. After I filled the oil I cleaned several spots and from what little driving I've done haven't seen more leakage. I'll know more tomorrow when I take my bike to the the track, it's about an hour away so that will give me a good idea. The pinion seal sounds easy enough, I'd like to go ahead and replace all the seals and give it the 200k tune up a little early. Like to be sure where it's leaking from though, I hate throwing darts at the board...

 

The shop manual calls for a non hardening sealant to put on the splines of the shaft. Got no idea what that is. Anybody know a brand or type of non-hardening sealant??

 

Permatex. Its junk for other purposes besides this one. Non-Hardening Pliable

 

agreed. Loctite also offers a good product.

 

Cool. I got the seal and other stuff yesterday. A good excuse to buy some more tools. I'm going to replace the seal today.

 

How'd it go ??

 

Well I thought it would take about 2 hours. But, after the first 2 hours I finally figured out how to get the bolts out of the drive shaft flange! I don't understand why Ford mixes metric and SAE, but the reality is I just had my head up my ***. So it started poorly and went down hill, but I finally got er done. Not my best work, but it turned out well. The good news is it was definitely the seal that was bad. There was oil all in the end of the drive shaft flange and it ran steadily as soon as I pulled the pinion out. As soon as I just put the new seal it stopped leaking even before I set it. So she's all back together and running well. I spent about an hour cleaning all the oil off the underside of the bed. Thanks for the help!