Rythmic hum after gear change

[scrota76]

I had new gears put in, 4.56 nitro gears. Also had the master rebuild kit installed. Did the break in, 4 heat cycles of mild driving for 20 to 25 minutes. Then had the fluids changed at about 200 miles. I used Amsoil 75w 90. As i was driving the Jeep home i noticed a rythmic hum at 70 MPH that goes away around 73 MPH. This started after the gear oil change. The gear oil in there for the break in period was nothing special.

I also had the tires balanced and rotated twice to see if that was the issue (unlimited rotation and balance at America's tire).

70 MPH is my cruising speed. The hum isnt that loud, and can be drowned out with music.

My questions are:

Should i be worried?
Any ideas what it could be?


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[Basscat]

I had new gears put in, 4.56 nitro gears. Also had the master rebuild kit installed. Did the break in, 4 heat cycles of mild driving for 20 to 25 minutes. Then had the fluids changed at about 200 miles. I used Amsoil 75w 90. As i was driving the Jeep home i noticed a rythmic hum at 70 MPH that goes away around 73 MPH. This started after the gear oil change. The gear oil in there for the break in period was nothing special.

I also had the tires balanced and rotated twice to see if that was the issue (unlimited rotation and balance at America's tire).

70 MPH is my cruising speed. The hum isnt that loud, and can be drowned out with music.

My questions are:

Should i be worried?
Any ideas what it could be?


Sent from my SM-G935V using WAYALIFE mobile app

Does it "hum" when coasting? When on the gas? Or both?
Have you narrowed it down to the ring and pinion gears or are you not yet sure where it's coming from?


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[scrota76]

I know its coming from the rear end. It did not start until after the gear oil was changed after the break in period. At 70 to 73 MPH it seems that letting off the gas to slow down makes the humming or slight vibration worse until im under 68 MPH. When slowing its no longer rythmic, just constantly loud.

I also had new axles put in during the gear change. And i know the mechanic put 3 quarts of gear oil, which is more than the recommended amount.

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[Basscat]

I know its coming from the rear end. It did not start until after the gear oil was changed after the break in period. At 70 to 73 MPH it seems that letting off the gas to slow down makes the humming or slight vibration worse until im under 68 MPH. When slowing its no longer rythmic, just constantly loud.

I also had new axles put in during the gear change. And i know the mechanic put 3 quarts of gear oil, which is more than the recommended amount.

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If it didn't start making the noise / vibration until after you changed the gear oil it's probably not preload on the pinion. I once had a ring gear do something similar and it turned out to be a bad gear. The finish or coating was bad and it developed an uneven surface. Had to change it out.


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