New Gear Break In

#1
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
 
#4
I posted about gear work in a thread about gear work, so if someone needs work they will know who to call. So will you talk bad about CFS because there work failed in your 8.8 as well?
did I say anything negative about anyone? I encourage anyone with a rear axle needing gear work to bring it to Performance 4x4 @ 803-466-4207. I said that he is great at gearing axles, especially ford 8.8s.
 
#6
I was poking fun at jimbo as he posted this thread, which includes an article by Randy that was posted in a previous thread on here.
 
#7
I posted about gear work in a thread about gears, so if someone needs work they will know who to call. So will you talk bad about CFS because there work failed in your 8.8 as well?
and to clear this up, the gears did not fail in my 8.8. The arb did. The gears have been quite from day one and even when the arb was in pieces. ARB is warrantying the locker as they see this as a manufacturing defect, it just took this long to show its head because I dont beat on my jeep enough evidently.
 
#13
Did I say the gears failed? But since we are clearing things up in this thread I got something to add. Matt got the gears that are in your rear axle now warrantied, even though they were not broken in properly, and over heated.
I don't know what he told you, but I drove the first gears in 30 min intervals and changed the fluid after 500 miles when I went back to tell him they were loud. I called him on the drive home and told him they had some noise and he told me that they would get quieter as they broke in... I drove from Matt's shop to Lexington to join my wife for dinner, then drove 76 home. Then I drove it from my house to the bus stop for two weeks. Nothing stupid and no long drives. I told him they were getting hot to the touch during this time. Eventually around 500 miles we opened it up and he said they looked fine. So you can just forget about me not breaking them in correctly. And for the record I asked him when I was leaving what kind of breakin I should do and he said just drive it you don't need to breakin gears.

When I came to him he gave me a price, and said he was getting his buddy who does a lot of work on ford axles to gear it,he asked for an extra $50 for that guy. Then when I picked up the jeep he told me that he ended up gearing it as his guy was busy.

When I got finished with my gears at cfs I left their shop and drove to Lexington, essentially the same drive as before, and I drove them the exact same way. They have never made a sound.

This has been hashed out plenty of times, can we put this to bed please? Something was wrong.
 

LBarr2002

LIFETIME
SUPPORTER
#15
So, since we're discussing gear break in...

I had 4.88's and ARB's installed in my 30/44 in the LJ. It's been a little over 500 miles, so I popped the covers tonight. I know that some shimmer in the oil is expected after break in, and I don't think there's an issue, but what's normal? Just curious because I've only had one other axle geared and I don't remember any shimmer in it after break in, but front and rear had noticeable shimmer in the oil of the LJ. The other axle was an 8.8 w/ 5.13's and welded, and I ran full synthetic. The LJ had conventional oil in it, but I'll be replacing with synthetic.
 
#17
So, since we're discussing gear break in...

I had 4.88's and ARB's installed in my 30/44 in the LJ. It's been a little over 500 miles, so I popped the covers tonight. I know that some shimmer in the oil is expected after break in, and I don't think there's an issue, but what's normal? Just curious because I've only had one other axle geared and I don't remember any shimmer in it after break in, but front and rear had noticeable shimmer in the oil of the LJ. The other axle was an 8.8 w/ 5.13's and welded, and I ran full synthetic. The LJ had conventional oil in it, but I'll be replacing with synthetic.
When I had my rear geared both times and when I had my front geared with 4.10s and then 4.88s there was some shimmer. I'm not sure how to quantify it, but that is why you change the oil after 500 miles right?
 

LBarr2002

LIFETIME
SUPPORTER
#18
When I had my rear geared both times and when I had my front geared with 4.10s and then 4.88s there was some shimmer. I'm not sure how to quantify it, but that is why you change the oil after 500 miles right?
Yeah, was just wondering because I've only seen one other break-in change. And with that one, I overfilled the axle because of having an aftermarket cover and still filling to the hole, so it probably had flake but was just diluted.
 
#20
The only other vehicle I have ever done a gear swap on is my 69 Camaro. I didn't do any sort of break in nor did I change the doping after 500 miles. I have never popped the cover since. I was like 16 years old and had no idea on what to do other than burnouts... I will be removing that axle for a 9" dropout in the next year or so, so I can report back then if I look at it before it goes in the scrap pile.
 
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