I recently installed a new set of gears in the rear axle of a 97 F150 w/ 8.8 rear. Things went well but I now have a whine in it only in the range of 55-65mph. Any suggestions on what I should change to eliminate the whine? All internal bearings were replaced; pinion bearing preload ended up around 28 in-lbs (spec for new bearings is 14-29 in-lbs). I had to tap the shims in with a hammer for the carrier bearings so carrier bearing preload should be fine. The gear pattern ended up centered well heel-to-toe on the drive side and was a little off-center (toward the toe) on the coast. It did end up a little closer to the face of the gear than the root but no matter what I did with the pinion depth I couldn't get it to move toward the root. The pattern did not run off of the end of the face of the tooth. Backlash ended up at .0095 - .00105 (spec is .008-.0012).This is the first ring/pinion I've ever set up. Any suggestions? Thanks in advance for your help.

 

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What kind of gears did you buy?
You did not buy a set of "pro gears" did you? Often times some gears are too hard for the street and even with a decent set-up, they make noise.
Usually a noise that is specific to speed would indicate a bearing problem. Did you keep the carrier bearing caps on the correct side, and did you make sure that hey were installed exactly as they were removed? Sometimes a cap that is turned upside down can cause a bunch of trouble.
The last thing I might think of is the accuracy of your instruments. How confident are you with the accuracy of your dial indicator? Those tolerances are pretty tight, and an indicator that is not accurate can vary those measurements in a bad way.
Many dial indicators and calipers come in a nice wood box that is lazer cut foam lined, and are not intended to be floating around in a drawer of a tool box. If your measurement instruments are not how shall I say,,,,, "dead nuts", you may not be accurate enough to be within tolerance.

 

They are from Superior Axle and Gear and are supposed to be for the street. They are not a pro or racing set.

I was very careful about the bearing caps. I marked them before I disassembled anything and kept everything organized. I'm sure they're not upside down.

My dial indicator isn't top of the line but it's not a $10 cheapy either. I think it's accurrate.

There was no checking distance scribed on the end of the pinion on this gear set. There was a "0" though, and the gear ID to match the pinion with the ring. I contacted superior gear tech support before the install and they said the "0" meant that it matched original factory specs. a +1 would mean .001" thicker pinion shim required, +2 = .002, etc. I asked what the factory default shim is and he couldn't tell me. He said to start with the one from the old set and check mesh pattern and adjust from there. The old set had a .028 shim in there so I started with that. I ended up with a .030.

I'm starting to think it could be pinion preload. I replaced the crush washer with a shim kit from Ratech. I was right at 28 in-lbs during assembly, and it was repeatable everytime I took it apart during the setup process, but who knows?

I'm working on the front axle now. Hopefully it will go better. Then I'll pull the cover and check the mesh pattern after driving it a 100 miles or so.

Any other suggestions? Thanks for your reply.