Rear end whining is generally caused by the backlash on the gears being set incorrectly. If you have a way to check the backlash, that would be a good place to start. Replacing your fluid is another thing to try after you've verified backlash is set properly.
After replacing my gears, they whined a little. After 500 miles I replaced the fluid and the whining dropped significantly. After 10,000 miles and replacing the fluid once more with 3 quarts of Royal Purple 75w140 (comes with friction modifier in the bottle already) I don't hear it anymore at all.
As for wear pattern, I am no expert on that. So I don't know!
Does anyone know if the wear pattern is the final once-and-for-all determinant of whether the gears are set right in evey way; or is it possible to have a good centered wear pattern and still have incorrect set-up?
To the OP -- it is hard to tell from the photos; and usually a shop will die a few teeth and then create the pattern so you can really see it; but they do seem fairly well centered. However the wear seems to be covering the entire tooth and I'm not sure what that means. I am not an expert on this; all I know is when I had my gears changed, they whined; so I took it back and the shop checked the wear pattern with die on the teeth; and the wear marks were about 2/3 of the width of the tooth and pretty much centered in the middle of the teeth. They said that was as good as it gets . . . . and the gears still whine.
and no, I did not read stlwagon's link, that might explain it!
Wear pattern is the best indicator of a good setup. Of course, I've seen some gears with a rock-solid install that still whine (Motive Gear is notorious). I found the best way to mitigate a noisy set of gears (short of replacing them) is to use good ole' dino-based oil with Ford friction modifier.
I set the backlash to ford spec of .09. The problem i have is it usually whines the loudest at 40-50 MPH mostly during deceleration. I can hear it a little during acceleration but it gets extremely loud during deceleration. If you look at the 5th picture doesn't it look like the wear is only on the top half of the tooth? From STLWagon's link it looks like the wear is supposed to be in the center with no wear on the tip of the tooth or down to the bottom of the tooth.
I have ford racing 4.10 gears and motive bearing kit. The spider gears in my original differential broke a couple teeth so i replaced it with a Detroit Locker 913A561 Trutrac Differential with 31 Spline for Ford 8.8. When i was breaking the gears in i accidentally put the brake pads on incorrectly which caused the brakes to get stuck pressing on the rotor. Do you think the drag caused by the brakes could have damaged my gears/bearings?
Let me rephrase... The crush sleeve may not have been crushed properly. If it's not, the pinion yoke will be loose and the pinion bearings won't seat right. It takes 300-400 lb-ft to crush the crush sleeve.
Oh really then I must not have put enough torque to it. I used an air gun that is normally used for taking lug nuts on and off of tires. I'm not sure the torque rating of the gun.
I think it's salvageable, but you may need a new crush sleeve.
You're not looking for a certain amount of torque on the pinion nut. What you need to achieve is a certain amount of preload on the pinion bearings, and this is done by measuring rotational resistance. Place a beam-style torque wrench on the nut and observe how much torque it takes to freely rotate the flange. It won't be much. When I rebuilt mine last year I torqued the new bearings to 25 lb-in of preload.
The high amounts of torque mentioned are just in reference to how hard it is to crush that sleeve. When I did mine, the car was on jackstands, and lemme tell ya, it would have been SO much easier with a hoist. You can get much more leverage if you're able to stand underneath the car.
That's a good question. Last year as I was finishing up, before installing my driveshaft, I thought I'd check (just out of curiosity) to see if the weight of the carrier, axles, etc. changed anything. It didn't.
With new bearings and clean gear oil, there was absolutely no change in rotational resistance. Mine showed 25 lb-in, whether I was turning the whole axle, or just the pinion gear.
I will look into the preload this weekend and post back what i find. Thanks guys for your help.
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