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There is a VERY important break in procedure when a diff has new parts. Are you aware of this?

YUKON GEAR AND AXLE CO.

New Gear Break-In
All new gear sets require a break-in period to prevent overheating damage. Any
overloading or overheating will break down the gear oil, which will cause the ring
and pinion to fail. This can be determined by inspection and will void the gears’
warranty.
Please follow these guidelines to insure proper break-in.
Avoid heavy acceleration during the break-in process.
Drive the vehicle lightly for the first 15 to 20 miles and stop. Let the differential
cool before proceeding.
Avoid heavy acceleration for the first 100 miles.
Drive the vehicle at least 500 miles before towing to retain the gears’ warranty.
When towing for the first time, drive for a very short distances (less than 15
miles) with the full load and stop. Let the differential cool for about 20 minutes
before proceeding. Repeat this procedure two more times (45 miles total) to
fully break in the gears.
Change the oil after the first 500 miles. This will remove any metal particles
and phosphoric coating shed by the gear set during the gears’ break-in period.
These towing instructions may seem unnecessary to most people, but we have
seen many differentials damaged from being loaded before the gear set was fully
broken-in.
OVERLOADED OR OVERHEATED GEAR
OIL WILL BREAK DOWN
AND DESTROY THE RING AND PINION!