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This morning, I jumped back into this. The LubeLocker gasket came open nicely. It’s nice not having to clean old gasket and RTV off of anything. The actual wear pattern on the gears was easy to see in the attached photo. Even though the pinion is not running off the face/edge, it is clearly on the shallow side and appears to me that it could be moved towards the flank/root.
The OE pinion shim was .036 and left a classic half moon, the pinion being too close/deep. I didn’t take a picture, but I’ve attached the image from the Yukon install manual that depicts it.
After 4 setups, I’m at .028 right now. Even though the pattern appeared suitable, the whine on acceleration suggests the pinion is still too far/shallow, so I’m going to split the difference and add .004 to see if I get a decent pattern. If not, it’ll be narrowed down. Even with the worst case scenario, at .001 increments, I only have a few setups left. There’s light at the end of the tunnel.
I also picked up a crush eliminator, but I havent decided if I’ll use it, or another crush sleeve. The crush sleeve wasn’t that bad the first time, despite the horror stories I’d read.
Game on! .028 .036 (OE Pinion Spacer)
Last edited by YetiX; Dec 27, 2025 at 12:35 PM.
Reason: Add Photos
.030. Appears suitable. Not much different than .028, which was whiny at 55mph+, but hopefully the extra .002 is the fix for the whine. I'm going to button it up and give it a try. .030 .030
No dice. Now it whines briefly at takeoff, then is quiet until 50mph, then the whine returns. The whine is still only on acceleration. Basically, no change. I guess it’s not surprising, given the similar pattern between .028 and .030. Backlash was set at 6 again, within the range of 6-10 from Yukon.
The day wasn’t a total loss. I replaced my tired looking flange/yoke with a new one while I was in there. I had previously noticed the OE flange was shedding metal where the pinion nut clamps down and the splines were looking worn in spots.
Looking forward, I’m inclined to go back to .032 which I posted previously. It appeared a touch on the deep side to my eye, but left a much more defined pattern in the paint. Maybe that will yield different results. I’m also considering just putting my original Ford 3.73 gears back in.
If anyone has any thoughts on those patterns, I’d appreciate it.
Now it’s time to order more nuts, crush sleeves, and seals.
It used to be back in the day, like 20 years ago, Yukon had a reputation for having noisy gears. No problems with them otherwise just on the noisy side due to them being of lesser manufacturer quality runs. Not sure if that still holds true today.
It used to be back in the day, like 20 years ago, Yukon had a reputation for having noisy gears. No problems with them otherwise just on the noisy side due to them being of lesser manufacturer quality runs. Not sure if that still holds true today.
Thanks for sharing. I’m starting to think gear quality may be the issue given that both patterns I’ve run appear suitable and the wear on the ring is in the proper spot. Other observations; the finish on the OE Ford gears is noticibly superior, the threads on the Yukon pinion were not great and required a 7/8-20 die right out of the box, and the Yukon pinion is extremely tight on the outer pinion bearing when assembling and disassembling, unlike the Ford. It’s not expensive to set it up differently, but it is time consuming. Yukon may get one more try out of me.
Having slept on it, .028(previous setup) was quieter than .030(current setup). Maybe I’m headed in the wrong direction. Perhaps I should head shallower than .028 and see what happens. At this point, it feels like I’m throwing darts blindfolded. I’m still mulling over my next move.
I watch a lot of Off Road youtube videos,
and nearly all of the fabricators say that Yukon is the best today, and for a competitive price...
Yukon sponsors a lot of off-road YouTubers. They're literally paid to say good things about their sponsors products. Like do you really think they all love the crap-tastic Milestar tires they all run?
...
Last edited by Antonm23; Dec 29, 2025 at 02:02 PM.
OP, you're likely wasting time (and gear oil) continually resetting the gears. IMHO that last drive side pattern you posted (in post #18 above) is fine. If that's where the gears still are, then I say run-em, do the recommended break-in procedure, and reevaluate noise after the break in.
...
OP, you're likely wasting time (and gear oil) continually resetting the gears. IMHO that last drive side pattern you posted (in post #18 above) is fine. If that's where the gears still are, then I say run-em, do the recommended break-in procedure, and reevaluate noise after the break in.
...
This thread got me thinking,,, I probably don't know how much noise is "normal" after a gear swap.
Yeah, I've done a few re-gears, but they've all been on either drag race stye cars (with loud exhaust systems) or 4x4 rigs with big aggressive tires (and some of the 4x4's had loud exhaust too). My most recent gear swap (on a Jeep JK) still had the stock exhaust, but it did have 37 inch mud tires (hence why it needed a gear swap, poor underpowered V6 could hardly pull the 37's), I suppose the extra noise of big tires, loud exhaust, (or just the noisy diesel engines in the trucks) could mask a small gear whine.
Let us know if the noise changes following gear break-in please.
...
Last edited by Antonm23; Dec 29, 2025 at 11:04 AM.
To be clear, the noise I hear is easily drowned out by the HVAC fan on the lowest speed or the radio. But it’s there, unlike the OE gears, which run silent. I’ll do a bit of break-in driving this week and follow up with the results. Thanks again!
After Yukon suggested that my pattern was a bit deep, I reset the gears once more. This time, I checked .025 and .026, both clearly shallow, before settling at .027, based on a pattern that was indistinguishable from the previous one on .028. The backlash was set to 9, within Yukon’s range of 6-10.I crushed the preload to 28, sealed it up and went for a drive. It made no difference at all. The gears still had an audible whine at takeoff and above 40mph on tip in/acceleration. Disappointing, to say the least.
I reinstalled the OE Ford 3.73 pinion using the same bearings from the Yukon overhaul kit and the OE Ford pinion shim. I replaced the Ford carrier shims with the Yukon shim kit and set the backlash to 14, between Ford’s preferred setting of 12-15. I got a perfectly silent and smooth ride on the first shot.
Ultimately, I prefer the quiet ride of my OE Ford 3.73 over the slightly improved shifting of the 4.56. For those with oversized mud tires or loud exhaust, I doubt the whine would be noticeable, but my Ex hauls the family and our boat. Quiet and smooth is the expectation. The acceleration whine from the Yukon ring and pinion wasn’t acceptable to me.
To be fair to Yukon, I would recommend their overhaul kit to anyone servicing a Sterling 10.5. It had quality Timkin bearings, nice shim kits, and all the fasteners you need. It was easy and worked well. Unfortunately, the gears I received were not reasonably quiet. I know there are many reasons this outcome may have occurred, but based on my experience, I would not buy Yukon gears again.
In the end, all my howling and pitted bearings and races have been replaced and my differential is smooth and quiet in a way I’ve never known it. Thanks to those that helped me out. I learned a lot and wouldn’t hesitate to tackle this job again.
Yes, that would be my approach next time. For me, the gear change was just an opportunity to upgrade while I was in there doing bad bearings. It wasn’t a necessity.
I wouldn’t hesitate to put a set of OEM 4.30’s in there. Maybe I’ll be able to get my hands on a set this year and put them in when it’s time to change the gear oil next year.
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