albaker

I have a 2003 F-150 4WD and noticed a vibration a couple days ago, so I crawled under the truck to see differential oil all over. It's leaking from the front seal/pinion seal of the differential where the axle attaches to the differential. I presume the vibration is from a bearing that is located behind the seal, but I've not taken one apart, and I can't find a video for repairing this seal/bearing. Does this sound like the bearing behind the pinion seal? Can this be repaired without taking the differential apart? Has anyone created a video or notes for this repair?

VeloSix

How many miles? Are you sure the u-joint is good? A shaft bearing will not cause a vibration when they start to fail, they will "hum" and be noisy. When the needle bearings fail inside a u-joint it will definitely cause vibration. Similar to an unbalanced wheel, but higher "frequency" as it is spinning at a higher rate that the tires. Its usually the rear u-joint at the diff that fails first.

Nun Ya

This ^^^^^^


Here's a video for changing the pinion seal.

PerryB

I'd bet the forward pinion bearing has failed, they're always the first to go if the diff. oil gets low because they are furthest away from the oil. After the bearing gets a little sloppy the pinion shaft starts to gyrate (which accounts for the noise and vibration) and then the seal fails. You need to get it examined by a competent rear-end shop soon, or the out-of-alignment pinion will start to chew up the ring gear.

PerryB

As the pinion bearing fails the end of that 5(ish) foot long shaft is no longer on axis, it's orbiting and most definitely WILL vibrate. I do agree the rearmost U-joint is the most common failure item, but when considering the seal failure, I don't think it's a coincidence. I think the bearing failed and ate the seal.
To the OP : If it IS a U-joint failing, the two most common symptoms will be either a metallic "ping" sound when alternating between drive and reverse and/or a rhythmic squeak as you pull away from a stop. Kinda sounds like " Weeky weeky weeky..." Increasing in frequency with speed. In the case of a joint failure, the described symptoms will usually manifest long before it gets bad enough to create a vibration you can feel.

albaker

Sorry all for not include the mileage. It's 245,000. Thanks to all who replied. My first thought when I climbed under the truck is that it was probably the U joints, but I wasn't able to get them to wiggle. I'm family with the "ping" sound, and that or the squeak are not symptoms of this problem. I replaced the front and rear * joints around 150,000 miles or so. The vibration is definitely much higher frequency than an unbalanced wheel. I've stopped driving the truck until I get it fixed.

I've not heard any noise until yesterday, and definitely no hum. It was more of a grumbling sound. Of course, this truck is a beast - it's the CNG with the 7700 suspension, and it's very loud normally. The video was great, so thanks for posting. I went to O'Reillys to get the bearing, and they told me there is both an inner and outer bearing. This video only replaces the outside. Do you have any idea what the possibility that only the outer bearing needs to be replaced?

Thanks again.

PerryB

If it IS the forward pinion bearing (that's my suspicion) you'll likely have to pull the ring and pinion to get the race out. Just changing the bearing cone without doing the race is going to be a short lived repair unless the race is perfect, and thats just not going to be the case. If you have to pull it apart, re-bearing the whole thing, including the carrier and axles.
P.S. -- Your description of a grumbling sound is textbook for a pinion bearing.

RLXXI

Also requires special tools, you'll have to set pinion depth and torque drag before you can put the carrier back in.
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VeloSix

I really don't feel a sloppy u-joint until the drive shaft is removed - then it's obvious.