We just needed to replace the pinion bearing in the differential in my wife's F150, a 1999 XLT SC with 4.6L engine at 45,000 miles. It also has the trailer tow package option and limited slip differential. I was surprise that the diff lasted only this long!

The truck is primarily a daily driver and its hardest work is towing a horse trailer about 6 times per year (past 2 years only) with a total weight of about 5,000 pounds.

The truck is repaired and the noise and harshness is gone, but the owner of the shop that did the repair is recommending that we sell the truck and replace it with an F250. While the heavy duty series would certainly be able to handle more weight, is it really necessary to do this upgrade for the job at hand. The way the truck is set up, it is rated to handle about 6,800 pounds.

TIA,
Joshua

 

What distance are we talking about?

6 trips X 2 years x (how many miles) = Total miles towing 5k

 

Good question, I should have mentioned that.

I estimate 750 to 1000 miles per year pulling that load. The rest of the miles are unladen. So that means a maximum of 2,000 of the 45,000 miles were pulling the trailer.

 

Simple, it was just a bad bearing, nothing major, happens now and then. I have seen brand new bearings, installed right, last like 10K with a balanced drive shaft. You just have crappy luck thats all . Other thing could be your drive shaft is unbalanced, and that caused the bearing to go quickly, or your u-joint is bad, and it caused a vib that wrecked the bearing. was there oil leaking out the front of your diff (around the pinion seal) before the fix? Plus, did your rear diff oil look ok when drained, if it was full of water or something that could have caused it, plus if it was low it would have burned out the pinion bearing quick. there is lots of things besides a 1000K of trailer towing a year to blame.

 

I tend to agree with the previous post, that being it was just plain bad luck, bad bearings, and the result of mass mass production. I am in the process of replacing bad carrier bearing in my '98 with the 4.6. While we are into it we will replace everything: carrier, pinion, etc. Actually I'm springing for new 4.10 gears as long as we will have it apart anyway.

I'm not happy to drop 1k+, but hey it's still cheaper than making payments on an '04.

Come to think of it I'd be happy to drive that '04 if anyone would care to pick up those pesky monthly payments.

ENB

 

Coraldoc,

Just a thought for your next truck. The 4.6 gets the 8.8 rear end. The 5.4 gets the 9.75 rear end, and I believe the v-10 in the F-250 is mated to a 10.25 rear end. So you and I have the same small differential, but we didn't have gear failure. Heck I had rear end oil changed 10k miles ago, but the new oil was definately toast with the heat thrown off from a bad bearing.

Good luck with that new bearing.

ENB

 

Thanks for the feedback.

There were no leaks from the differential.

The technician reported that the oil looked to be in good condition, except for the metal particles from the bad bearing. He assured me that he did a very thorough flush of the differential and used appropriate synthetic diff oil.

We'll see how long this repair lasts and make any truck replacement decisions if the failure occurs again.

Until this issue the F150 has been extremely reliable with no other non-maintenance servicing needed.