I have a 2004 f250 4.30 gearing rear end. I replaced the bearings in it three years ago and have covered 35,000 miles since then. 18,000 miles of that was towing. My GCWR is 17.250lbs. The camper loaded is 9300lbs. Ford 75/140 synth fluid. Nothing is overloaded and travelling at 65 on the interstate for extended periods of time towing my diff temperature never exceeded 204 degrees, even in 90 degree weather. So I began to hear some whining back there so I pulled the cover. Bearings looked good but there was slack in the carrier bearings and so I went through the whole thing again. New pinion bearings, new carrier bearings, I had great pattern on the ring gear pinion. Backlash was at 12 thousands which is within spec from Ford for the Sterling. My question is what would cause all that wear in the bearings.? Replacing them brought the thing right back into spec. My backlash when I heard noise was 18 thousandths. I am working it, but I figured it should last a lot longer than what it is doing. I have run it 15,000 miles since the rebuild, half of that towing my camper. It started out at 12 thousandths and it is already at 15 which is the outer limit of specs. Any thoughts would be appreciated.

 

I can't speak to what your issue is, as I have no idea, maybe a warped housing, or mis-aligned caps? Regardless, I'd expect a hell of alot longer than 35,000 miles out of a set of Differential bearings. I *regularly* see OBS with the 10.25 Sterlings with a couple of hundred thousand miles on the original bearings.

 

My guess would be not enough side bearing preload.

 

The shims for carriers went in real tight and I didn't mix them up. thanks for your reply.

 

A guy told me tonight who rebuilds rear ends that if I put the right side shim in after the carrier that there will not be enough preload on the carrier bearings. I have never heard of this.. He said that the two shims should be put in the housing then put the carrier in. anyone got any experience with this. I put the left shim in, then the carrier and then the right shim which went in half way easily then I had to get a bronze driver and tap it into place and it was tight, so much so that I thought the shim would break. . Thoughts appreciated thanks

 

First I've ever heard of that. The preload on the pinion doesn't have anything to do with the carrier bearings. That's set with the pinion bearings.

 

Once you had the carrier in and the bolts tightened down did you set up a dial indicator and pry the carrier with a long bar back and fourth to see if there was any movement on the indicator ? You can't go by just the degree of difficulty of getting the carrier into the housing.

 

Thanks for your thoughts guys. I did pry it left and right to see if there was any movement and there was none. But after towing 15k and total of 35k there was carrier bearing movement sideways. The pinion stayed fine.

 

Sfaulken, you helped me. I made a typo and said pinion, but meant to say carrier. Sorry about that, thanks for helping me catch that error.

 

The only thing I can think of is if you add shims to the side that will force the ring gear into the pinion first that could give you a false sense of preload. Maybe that is what that fellow meant.

 

Well I have decided to let the guy rebuild my rear end. I have yukon gears and installation kit coming and a eaton truetrac from summit racing. I will enjoy not having the clutches and LS to deal with and he is going to set it up right. The only problem I am having is that truetrac wants non synthetic 75/90 in it, and the ring gear and pinion wants 75/140. synthetic.

 

The ring gear and pinion don't care. They're solid pieces of metal. If it makes you feel better, give Yukon a call and verify, but I promise you, they don't care in the least, whether you're feeding them 75w90 or 75w140, or whether it's synthetic or not. Technically the true trac doesn't either, there's no friction anything in it. But as it's the bit with the moving parts and more expensive, I'd go with the oil it calls for.

 

The TrueTrac relies on the friction between its gear teeth and gear housing to provide the limited slip function, so if you use something too slippery, it may not be as effective as a less slippery lube. I'm using a similar LSD in my 9" with 75-140 gear lube, and it grips just fine:

https://photos.google.com/share/AF1Q...ZEOUVmWjRfSFl3

The worm or helical gear type LSDs don't have a preference for synth or regular oils. But don't use a friction modifier like with the clutch type LSDs, as that WILL significantly reduce the friction of the oil.