Saw this online and thought it was interesting. I know this is a topic many argue about but this article was written by Randy of Randys Ring & Pinion:
New Gear Break-In
Do we really need to break-in a new gear set? I have heard many people say "When I bought my new truck no one
ever told me to break-in the ring & pinion." Whenever we are blessed enough to afford a new vehicle, we take it
easy on the engine for the first few hundred miles. While we are pampering the engine (probably for the last time
ever), the ring & pinion set goes along for the ride and gets a chance to break in before we hammer the throttle.
You just installed a new ring & pinion set and you’re ready to feel the power. Hold on, don’t burn rubber yet. That
new gear set may become scrap metal faster than you can say "burned gear syndrome".
In most stock vehicles with stock tires there is seldom a risk of a burned gear set. For those of us who modify and
use our trucks, there many situations that can contribute to burned gear syndrome; RV’s, towing, tall tires, and high
numeric gear ratios (4.56 & up) can all generate a lot of heat and cause the gear oil to break down. The greatest
damage to a new gear set results when it has been run for ten minutes or more during the first 500 miles and the oil
is very hot. Any heavy use or overloading while the oil is extremely hot will cause it to break down and allow
irreversible damage to the ring & pinion.
In order to make them run cooler and quieter, new gears are lapped at the factory. However, they are not lapped
under the same pressures that driving creates. The loads generated while driving, force any microscopic high spots
on the gear teeth back into the surface of the metal. This is called "work hardening". Work hardening is similar to
forging in the way that it compresses the metal molecules into a very compact and hard formation. This can only be
accomplished if the metal surfaces are lubricated and the gear temperature stays cool enough that the molecular
structure does not change. If the temperature of the metal gets hot enough to change the molecular structure, it will
soften the surface instead of hardening it. This may seen like a balancing act but it all happens easily & passively as
long as the oil keeps the gear cool while it is breaking in. Some of the synthetic oils on the market today can help a
gear set live longer. These oils will continue to lubricate at temperatures where many crude oils break down.
Even with synthetic oils, I still recommend the following procedure for breaking in a new gear set: After driving the
first 15 to 20 miles it is best to stop and let the differential cool before proceeding. Keep the vehicle at speeds below
60 mph for the first 100 miles. I also recommend putting at least 500 miles on the new gear set before heavy use or
towing. During the first 45 miles of towing it helps to go about 15 miles at a time before stopping to let the
differential cool for 15 minutes before continuing. This is necessary because not all of the gear tooth is making
contact until it is heavily loaded. When towing, the teeth flex to contact completely, and cause the previously
unloaded portion of the teeth to touch and work harden. All of this may seem like paranoia, but it is very easy to
damage the ring & pinion by overloading before the teeth are broken in. If you take it easy on a new ring & pinion
and keep it full of high quality oil, it should last a lot longer. It is a good idea to change the gear oil after the first
500 miles in order to remove any metal particles or phosphorus coating that has come from the new gear set. This is
cheap insurance and a good time to discover any problems before they grow to disastrous proportions.
Written by Randy Lyman, founder and President of Randy's Ring & Pinion
New Gear Break-In
Do we really need to break-in a new gear set? I have heard many people say "When I bought my new truck no one
ever told me to break-in the ring & pinion." Whenever we are blessed enough to afford a new vehicle, we take it
easy on the engine for the first few hundred miles. While we are pampering the engine (probably for the last time
ever), the ring & pinion set goes along for the ride and gets a chance to break in before we hammer the throttle.
You just installed a new ring & pinion set and you’re ready to feel the power. Hold on, don’t burn rubber yet. That
new gear set may become scrap metal faster than you can say "burned gear syndrome".
In most stock vehicles with stock tires there is seldom a risk of a burned gear set. For those of us who modify and
use our trucks, there many situations that can contribute to burned gear syndrome; RV’s, towing, tall tires, and high
numeric gear ratios (4.56 & up) can all generate a lot of heat and cause the gear oil to break down. The greatest
damage to a new gear set results when it has been run for ten minutes or more during the first 500 miles and the oil
is very hot. Any heavy use or overloading while the oil is extremely hot will cause it to break down and allow
irreversible damage to the ring & pinion.
In order to make them run cooler and quieter, new gears are lapped at the factory. However, they are not lapped
under the same pressures that driving creates. The loads generated while driving, force any microscopic high spots
on the gear teeth back into the surface of the metal. This is called "work hardening". Work hardening is similar to
forging in the way that it compresses the metal molecules into a very compact and hard formation. This can only be
accomplished if the metal surfaces are lubricated and the gear temperature stays cool enough that the molecular
structure does not change. If the temperature of the metal gets hot enough to change the molecular structure, it will
soften the surface instead of hardening it. This may seen like a balancing act but it all happens easily & passively as
long as the oil keeps the gear cool while it is breaking in. Some of the synthetic oils on the market today can help a
gear set live longer. These oils will continue to lubricate at temperatures where many crude oils break down.
Even with synthetic oils, I still recommend the following procedure for breaking in a new gear set: After driving the
first 15 to 20 miles it is best to stop and let the differential cool before proceeding. Keep the vehicle at speeds below
60 mph for the first 100 miles. I also recommend putting at least 500 miles on the new gear set before heavy use or
towing. During the first 45 miles of towing it helps to go about 15 miles at a time before stopping to let the
differential cool for 15 minutes before continuing. This is necessary because not all of the gear tooth is making
contact until it is heavily loaded. When towing, the teeth flex to contact completely, and cause the previously
unloaded portion of the teeth to touch and work harden. All of this may seem like paranoia, but it is very easy to
damage the ring & pinion by overloading before the teeth are broken in. If you take it easy on a new ring & pinion
and keep it full of high quality oil, it should last a lot longer. It is a good idea to change the gear oil after the first
500 miles in order to remove any metal particles or phosphorus coating that has come from the new gear set. This is
cheap insurance and a good time to discover any problems before they grow to disastrous proportions.
Written by Randy Lyman, founder and President of Randy's Ring & Pinion