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Discussion Starter · #1 ·
2002 Ford F-250 7.3L

I have been seeing an oil leak at the back of the truck. After inspection it looks like it was leaking from the bottom of the differential. Took the plate off and drained what little oil was left. Cleaned everything up and rebuilt the gasket and put new oil back in the differential. Next day I am still seeing a small oil leak. Pretty sure it is not my gasket. I am thinking that it is leaking from the slip joint, down the casing, to the differential and then the ground. Also hearing a very small roaring noise when accelerating. So, I am trying to figure out if it my bearing, u-joint, or what that might be leaking and making the noise. I have seen some posts about just greasing the slip joint, but not sure if that is my problem or not (that seems to be more for a clunking noise which I do not have). Any ideas to help me figure this out?? TIA.
 

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IF your truck underside looks anything like mine it is really hard to spot just how many or where a leak is coming from. Go to carwash and get it as clean/dry as possible than do a good inspection with a light, drive 5 miles and repeat. Oil moves all over once it is in the wind. Slip joint has no oil so I don't think that is it.
DENNY
 

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Lift the rear wheels off the ground and put the rear end on jack stands. With key off, crawl underneath. While moving the driveshaft back and forth, look for ujoint movement.

You can also turn the motor on, put it in drive and listen for noise.
 

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If the wheels are off the ground, even putting it in neutral will get you a little spin and will be a bit safer should you decide to get tangled in something.
 

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Discussion Starter · #5 ·
Ok. Sorry for the confusion.. I had my terminology mixed up. After further inspection it appears that the leak is coming from the pinion seal. I can't figure out how hard of a job this is to replace the seal. It seems like the hardest part may be getting the yoke off and the nut torqued to spec. Any instructions or ideas if this is a job that is easy to do??
 

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There are two ways to do the pinion seal job - the right way and the way most everyone seems to do it. The right way involves getting a new crush sleeve and having an inch pound torque wrench to measure the bearing pre-load. This is complicated by the fact that the exhaust on one side and the fuel tank on the other prevent you from getting even the smallest torque wrench to spin while taking a reading. It's really a job best done with the axle on the workbench.

What most people seem to do is mark the pinion nut (hit it with a punch on the top to make an indelible point of reference) and then count exactly the number of turns it takes to get the nut off. Swap the seal and then put the nut back on with exactly the same number of turns. Theoretically, that should get the bearing back to the same preload it was when you started.
 

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Discussion Starter · #7 ·
There are two ways to do the pinion seal job - the right way and the way most everyone seems to do it. The right way involves getting a new crush sleeve and having an inch pound torque wrench to measure the bearing pre-load. This is complicated by the fact that the exhaust on one side and the fuel tank on the other prevent you from getting even the smallest torque wrench to spin while taking a reading. It's really a job best done with the axle on the workbench.

What most people seem to do is mark the pinion nut (hit it with a punch on the top to make an indelible point of reference) and then count exactly the number of turns it takes to get the nut off. Swap the seal and then put the nut back on with exactly the same number of turns. Theoretically, that should get the bearing back to the same preload it was when you started.

So there is no flange or stop for the nut at the right position? I thought I read that somewhere?? So the issue is that if you don't get it correct then you will either damage the crush sleeve or have a wobble at high speeds?? On another note, what is the best way to get the yoke off of there??
 

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The crush sleeve sets the space between the front and rear pinion bearing. If the nut is too loose, there will be no preload on the bearing and the pinion can chew up the ring gear. Too tight and the bearings can chew themselves up. There is no stop. There is on a Dana 80, but the Sterling works differently. To pull the yoke, use a two jaw puller and two long bolts. I leave the nut on threaded so it is flush with the end of the pinion so you don't do any damage to the threads.


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