Complete credit for all of the below goes to Hammer Z71.
What Gears Are for You?
The Proper Break In Procedure for New Gears.
500 miles, NO Towing. The gears need to be heated and cooled repeatedly to seat and harden properly.
Rule of thumb here is:
First 200 miles, no more than 20 mins of continuous driving, followed by at least 20 mins of a cooling period. Vary your speed/rpms. No more than 45 mph.
Next 200 miles, no more than 40 mins of continuous driving, followed by at least 20 mins of a cooling period. Vary speeds. No more than 60 mph.
Next 100 miles, no more than an hour continuous, vary speeds, not to exceed 70 mph.
At 500 miles, change the fluid, as there will be small sand size filings present from break-in. Inspect the differential. There should be NO large filings present and the fluid should not appear "burnt". This change is important, not only to remove the small filings and visual inspection, but new gear sets ship with a phosphorus coating, that burns off during break-in. This coating should not be left in the gear lube for an extended period as it has shown to prematurely break down the viscosity and lubrication properties of the lubricant over time.
Contrary to what you may have heard, or what a shop may tell you, there should not be even a hint of a whine from properly installed aftermarket gears.
If all checks out well, replace the fluid and the pumpkin cover and then DRIVE IT LIKE YOU STOLE IT...
Towing, Tires, Gears, and your Transmission.
So, you just got a level kit and 35" tires and you tow regularly. What does this do to your transmission?
With EVERY change in final ratio of 1.0:1 your transmission temperature will increase or decrease by about 25 percent at given load, and remember, tire diameter has a direct effect on final ratio. Final or EFFECTIVE ratio is determined by the following formula: Old Tire Diameter / New Tire Diameter x Gear Ratio = Effective Ratio.
So, assuming you have 3.92 gears and go from stock size tires of say 245/70r17 to 35x12.5x17s. Your EFFECTIVE RATIO would change from 3.92 to 3.47, so if your transmission was running at about 190* with no load, it would now be running at about 212*, not a big deal. But if your transmission was running at about 220* while towing a decent load (about average) then with the 35" tires your transmission would be running at about 250* WHICH IS HOT! You don't even want to see these numbers if your truck has the stock 3.55 gears!!!
A tranny cooler will help some, but the bottom line is your transmission is still generating that much heat.
To tow well, even with 33" tires it would be very advisable to make a change to at least 4.10 gears and much taller then 4.56s would almost be a necessity. According to data provided by the American Camper Association, a stock Ram 1500 has a 1000# higher towing capacity with 4.56 gears as opposed to 3.92s given equal tire size and almost a 2000# higher capacity than 3.55 gears.
If you are towing regularly, a larger pan capable of holding more fluid would also be a good mod, as would a transmission temperature gauge...