Hi y’all,

After recently developing a constant growl from my differential, I suspected my pinion bearing(s) were due. I decided to overhaul the differential myself, and replace the original 3.73 ring and pinion with a new 4.56. I have newer Super Duty wheels with a 34” diameter, so the effective ratio should put me just under the 4.30 option that was originally offered from Ford. It should tow nicely.

Everything with the disassembly and reassembly went smoothly. The pinion and carrier bearings & races were completely worn and they were all replaced. I ran several patterns with the new ring & pinion and I thought I had it setup well, but I have a subtle whine at lower speeds which is clearly audible above 40mph. The whine is audible only on acceleration. Coasting is quiet. My new bearings are all quiet.

The original .036 pinion shim left me with a classic half-moon, the new pinion being too close. After several attempts, I landed on .028, which I’ve attached pictures of. I’m wondering if anyone with experience reading these can offer me some direction. Having never done this before, I’m clearly not seeing my pattern for what it is.

Thanks in advance,

Tom
2003 XLT RWD 6.8l

 

When I replaced the same parts in my 01 I had good luck the first time, I had never touched a diff before and went solely by the service manual. I also stayed stock with the exception of adding the Detroit Tru-Trac diff unit. The link below is of my rebuilding halfway in. There are pics from the shop manual of the gear mesh pattern, clearance and tolerance, that Ford suggests. Maybe this will help. Regardless of your new gear ratio, gear mesh is gear mesh. I also cheated on the crush sleeve, pics above that link, I remember I was doing something wrong when setting the pre-load on the pinion. I think I was supposed to use one of the tools I bought instead of the pinion nut. Hopefully my first go at this may help.


https://www.ford-trucks.com/forums/1...l#post20732175

 

Thanks for your reply. I had reviewed your thread when I was getting ready to do this job. Your photos and write up were helpful. I have everything in spec with regard to preload, backlash, etc. Anecdotally, I’ve read that whining on acceleration is due to the pinion being too shallow and only contacting the outer part of the teeth. I just don’t have the experience to see that in my last pattern. I’m hoping someone else will, or have another suggestion that isn’t obvious to me. As you know, it’s a bit of work to get in and out of there.

If I can’t make these gears quiet, I’ll probably go back to my OE 3.73. I wasn’t unhappy with them and prefer the quiet to the new gear ratio.

Pre-crushing the sleeve is a great idea. I’ll do that when I go into this one again. On my final assembly, I was able to get 25 on the preload with my new crush ring, but that was as much luck as anything. I now regret not doing a crush sleeve eliminator. I see now that I was overly confident I wouldn’t have to go back in!

 

Your gear pattern looks acceptable to me. I wouldn't have expect noise from that gear pattern. Pinion is on the shallow side, but the pattern doesn't run completely off the edge of the tooth or anything. How is the preload on the carrier side bearings?

Also, care to share what gear manufacturer the new gears came from (OE Sterling, Yukon, Nitro, Revolution, etc).
...

 

Thanks for the reply. I read the pattern the same as you. I may need to tighten up the carrier shims/preload. I didn’t document the measurement, but I was able to tap my shims in with a brass punch. Admittedly, not much effort was required, but it’s tight.



After thinking on your question, I could probably add about .005 to each side without hammering on it too hard and see what happens. If I understand where you’re going with that, I may have it too loose, therefore allowing the backlash to increase out of spec when it’s under load?





I used a Yukon 4.56 Ring & Pinion, part number: YG F10.5-456-31. I also used Yukon’s Master Overhaul Kit, YKF10.5-A, which contained Timken bearings on all sides. I’ve read the good and bad about Yukon, but given my novice status, I’m not ready to stop looking at my work yet.



Thanks again!

 

I've used Yukon gears a few times, always had good luck with them. Only negative thing I have to say about Yukon is the pinion seal that comes with their install kits doesn't seem to last very long before it starts leaking, but the gears/bearing/shims/crush sleeves/ etc. have always been good.

That said, it wouldn't be the first time a reputable company known for making quality parts changed the way they do business and started outsourcing ,,, which inevitably leads to bad quality (like Moog used to be top shelf / high quality ball joints not that long ago, now they're crap like everyone else). Hopefully Yukon hasn't adopted the Moog business model.
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After some more thinking about carrier preload, it occurred to me that I have the OE carrier shims on my workbench along with the measurements of the new ones I built;

OE: .282 & .293 = .575
New: .277 & .265 = .542
Difference: .033 (seems like an awfully big difference!)

I’ve reused my carrier, so the only change there is new carrier bearings. I’m definitely on the loose side of things. It seems logical that I should put an additional .016 on each side to get a total of .574 and see if that buys me silence. I’ll try that next. Thanks, again.

 

I agree, a 33 thousands difference in shim thickness (when reusing the same carrier, in the same housing) does seem like a BIG jump.

Did you put the shims between the bearing race and housing (like stock) or between the bearing and carrier (like some Dana axles do). It shouldn't matter as far as setup goes and both ways are acceptable, but it is harder to adjust when the shims are between the bearing and carrier because it requires pulling the bearings (but does make carrier installation into the housing easier because you're not fighting with the shims).
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My shims are on the outside, between the bearing race and housing, like stock. It is a bit of a wrestling match getting it all in there. Thankfully, the new “base” shim has a nice inner lip that all the smaller shims nest on top of, making it pretty manageable.

My new seal, gasket, crush sleeve, pinion nut, and oil arrives on Sunday, so it looks like Monday will be my day. Hopefully all I need is the gasket and oil! It would be a real treat not to pull the pinion again.

 

I definitely fought with the carrier shims as well.

 

I tend to put the carrier shims , especially the really thin ones, between the carrier and bearing, only leaving the one thick base, or master, shim between the race and housing. Mostly because it aggravates me fighting with the small thin shims trying to install the carrier and I've bent shims a few times.

Not that shims are expensive if you bend one, but when you destroy the only ones you have of a certain thickness, then you get to wait for a week for the brown truck to arrive again with the replacements. The thick maser shim doesn't bend easily and can be tapped in with a little more force, which allows me to get the preload on the side bearings I want with less cursing required.
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My supplies arrived early, so I was able to tackle this today. I picked up a new caliper, so I started with fresh measurements:

OE Ford Shims: .278 & .286 = .564

I popped the cover and found the drained oil was clean.

After 5 rounds of carrier shimming, I was satisfied I couldn’t get more than .552 worth of shims in the carrier without damaging something, regardless of configuration. That left .012 of “slack”, compared to the OE shims. Initially, I was .033 loose, so eliminating 21 thousandths of slack felt like a decent improvement. I’ve attached some pics of the shims with the retention lip that came with the Yukon kit.

I ended up with the following split:

New shims: .289 & .263 = .552

That setup resulted in a backlash of 6, which was just in range. Yukon recommends 6-10 for my gears. Given that I couldn’t get to OE specs with my carrier shims, I figured it was best to leave it on the tight side. If anything, whatever remains of that .012 of carrier slack will only cause an increase in the backlash. Hopefully, not enough to whine!

I ran a pattern and it looked exactly the same, which was expected as I didn’t adjust the pinion.

After that, I installed a LubeLocker gasket. It’ll be a treat not to scrape gasket material next time I open the diff up, hopefully not until the break-in period is over!

I also decided to tackle the rear wheel bearings while I had everything apart again. I ran out of daylight and only got one side done, so the test drive will have to wait until tomorrow, after I finish that up. Hopefully, all is quiet.

As always, comments and suggestions welcome. Thanks.

 

After finishing up the rear wheel bearings this morning, a few brief drives around the neighborhood haven’t revealed any gear noise up to 50mph. Much better, so far.

After a few more gentle drives, I’ll take it out for some highway speeds. Thanks for the help.

 

Is the diff cover gasket re-usable?

 

Yes!

I went for a drive today and I still have a whine on acceleration above 55mph. I'm going to have to adjust my pinion depth, so I'll let you know how the gasket works out when I seal it up a second time.