On Toyota trucks we recommend 4.88's for 33" tires and 5.29 for 35" and larger.

Ring & Pinion Break-In Procedure:
All new 3rd members require a break-in period to prevent damage from overheating. Any overloading or over-heating during this period can cause the gear oil to break down resulting in ring & pinion failure.
After installation;
Drive lightly for 20-30 minutes and then allow the differential to cool for at least two hours.

Avoid heavy throttle use during the first 500 miles.

Do not tow a trailer during the first 500 miles.

Change oil after 500 miles to remove any particles suspended in the oil.
This may seem unnecessary but it is very easy to damage the differential by loading it before the gear set is completely run in. New ring & pinion gears create excess heat when they are new. This excess heat can damage the heat treatment of the gears.