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gear break in

cams 76

Sr. Member
Joined
Jan 6, 2004
Messages
550
Loc.
brookings
i just re-did my gearing 4.56 detriot locker in the rear detriot tru-track in the front with 31 splines in the rear. how important is the break in process for the gears. i was told the first time i run it i need to go about 20 miles then park it for the the night then then take it easy on it for 500 miles and not to keep it at a constant speed. mine is not a daily driver and could take forever before i get to 500 miles of use
 

Devin

Bronco Kineticist
Joined
Apr 29, 2004
Messages
3,956
Make it a daily driver for a while until the break-in process is done.
 

bmc69

Contributor
Bronco Guru
Joined
Jun 11, 2004
Messages
11,849
What Devin said. What they really want you to do is completely avoid highly loading the gears untill the teeth mating surfaces are happy with each other and wear hardened..much like cam brake-in. That means limiting the loads and not lugging the truck at low speeds. New gears create a lot more heat until broken in too...so overheating of the oil and gears both (which can slow down or mess up the work-hardening process that is taking place) is a concern. But drive 'er nice and easy at normal speeds for resonable distances and you will be fine.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Only important if you dont want the gears to fail and have to spend more money on them.
Drive it about 15 min then let it cool. touch the housing it will be hot. You dont have to wait overnight just until its cooled down again. do this a few times and take it easy the first 500 miles then change the oil and you should be good to go.
Think of it like a new car most people just take short trips and drive real easy so things get broken in correctly because they are not hammering them.
 

70_Steve

Old Guy
Joined
Dec 13, 2002
Messages
8,317
I'm just finishing up almost the exact same swap. 4.56s w/Detroit in the back and an Ox Locker up front. I plan on making the Bronco a Daily Driver for a while, and also, when possible, run it in front wheel drive to make sure I've got some breakin and wear on the front gears. Theres and event I want to go to in 2 1/2 weeks and I want the gears broken in properly. I've got too much time and money invested to not break in the gears properly.
 

needabronco

Bronco Guru
Joined
Jul 2, 2004
Messages
6,411
Loc.
Prescott/Farmington
Not to hi-jack but do I need to worry about this if all I'm doing is adding a locker and changing out seals? I'm heading to the Stampede it 2 1/2 weeks, and may end up driving my bronco 400 miles there.
 

rednck21

Newbie
Joined
Feb 27, 2002
Messages
3,914
i was told i can drive it in 2wd but lock the front end in with the hubs for the break in.



you can do it like that, or since i had a detroit in the front i put it in 4hi and did not lock the hubs.
 

rednck21

Newbie
Joined
Feb 27, 2002
Messages
3,914
Not to hi-jack but do I need to worry about this if all I'm doing is adding a locker and changing out seals? I'm heading to the Stampede it 2 1/2 weeks, and may end up driving my bronco 400 miles there.

no. measure the backlash and run the pattern(take pics if you need to) before you take it apart so you can make sure its exactly the same when you put it back together.
 

tdc_worm

Full Member
Joined
Apr 17, 2007
Messages
349
Loc.
Austin
Only important if you dont want the gears to fail and have to spend more money on them.
Drive it about 15 min then let it cool. touch the housing it will be hot. You dont have to wait overnight just until its cooled down again. do this a few times and take it easy the first 500 miles then change the oil and you should be good to go.
Think of it like a new car most people just take short trips and drive real easy so things get broken in correctly because they are not hammering them.

not trying to be a jerkwad here, but am i to assume that when i buy a brand new car that the all of the drive components have been "warmed up" and let "cool down" several times and that the gear boxes and differentials have been broken in for 500 miles before i get the car? maybe they have and, if so, then i have been educated...i am inclined to believe that is not true.

my brand new jeep grand cherokee overland manual speaks nothing of taking it easy on the new limited slip differentials...it only recommends that i change the diff oil every 15000 miles.

if auto manufacturers put substandard equipment on the market that broke in the 1st 500 miles (rings and pinions included), then they would go bankrupt in a second. does anyone have any proof that anyone else ever broke a ring and pinion due to improper break in (or more likely due to improper set up)? i may be naive, but i would like to believe that the after market R&Ps are at least of comparable strength...
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
not trying to be a jerkwad here, but am i to assume that when i buy a brand new car that the all of the drive components have been "warmed up" and let "cool down" several times and that the gear boxes and differentials have been broken in for 500 miles before i get the car? maybe they have and, if so, then i have been educated...i am inclined to believe that is not true.

my brand new jeep grand cherokee overland manual speaks nothing of taking it easy on the new limited slip differentials...it only recommends that i change the diff oil every 15000 miles.

if auto manufacturers put substandard equipment on the market that broke in the 1st 500 miles (rings and pinions included), then they would go bankrupt in a second. does anyone have any proof that anyone else ever broke a ring and pinion due to improper break in (or more likely due to improper set up)? i may be naive, but i would like to believe that the after market R&Ps are at least of comparable strength...

I think some manufacturers do break in gears before the axle hits the vehicle and probably do a initial engine break in. Some gears are lapped before leaving the manufacturer which cuts down on intial break in also. But in reality they dont have the time to do it properly. If they did you'd get a car with 500+ miles on it new. Like I said when most people get new cars they tend to drive them easy so the break in is happening during this new car period. I dont think many gear sets fail even if not broke in properly but why take the chance. Now the after market is a whole different ball game as there are all kinds of different gear sets some hard some soft some in between all have slightly different applications. some gears are cheap and really need to be broken in properly but even some of the expensive gears are just as easily destroyed when not broken in properly.

...[/QUOTE]needabronco Not to hi-jack but do I need to worry about this if all I'm doing is adding a locker and changing out seals? I'm heading to the Stampede it 2 1/2 weeks, and may end up driving my bronco 400 miles there. ...[/QUOTE]
While not as big of a worry you are still resetting the gears It will be hard to get it exactly the same but since the gears are already broken in so to speak as far as heating and cooling cycles go and wear pattern it wont be as critical but I would still try to take it easy and change the oil at 500 miles because you will create a new wear pattern for the new setup. I would drive it for 15 min after you put in your new locker then carefully feel the housing if its too hot to keep your hand on then you need to follow the break in procedures if its only luke warm they you are good.
 

Big Del

Jr. Member
Joined
Oct 12, 2007
Messages
90
Loc.
JC Oregon
I'm not disputing this gear break in period, I was also wondering has anyone seen gear failure simply from not breaking them in. It's just like engines people say you have to break them in and there are all these theories about the correct way, if have an engine built at a shop with a dyno the first thing they do is full throttle after it has oil pressure.
 

tdc_worm

Full Member
Joined
Apr 17, 2007
Messages
349
Loc.
Austin
what are the signs that a gear failure has occurred from improper break in? what are the signs that gear failure has occurred from improper set up?
 

Steve

Bronco Guru
Joined
May 5, 2003
Messages
2,986
Loc.
Grand Junction, CO
what are the signs that a gear failure has occurred from improper break in? what are the signs that gear failure has occurred from improper set up?

Unless you know that they were installed correctly, if they were broken in and how many miles are on them you probably won't know. I know a guy here in town with a Jeep. We installed new gears so I am 100% certain they were installed and set up correctly since I've done bunches of gear installs. Even though I told him how to break them in he immediately hopped on the interstate and drove 75 mph for a while.

When we replaced those gears a week later they had very obviously badly overheated. They got so hot they had turned blue around the teeth, and then started swapping metal between them.
 

00gyrhed

Bronco Guru
Joined
Aug 3, 2006
Messages
2,428
Overheated ring gear

Unless you know that they were installed correctly, if they were broken in and how many miles are on them you probably won't know. I know a guy here in town with a Jeep. We installed new gears so I am 100% certain they were installed and set up correctly since I've done bunches of gear installs. Even though I told him how to break them in he immediately hopped on the interstate and drove 75 mph for a while.

When we replaced those gears a week later they had very obviously badly overheated. They got so hot they had turned blue around the teeth, and then started swapping metal between them.

Not that I doubt your skills, but that sounds more like a set up problem. Too little backlash, or perhaps the ring gear had excessive runout. Excessive runnout will cause a nice pretty pattern in one spot on the gear and the the backlash can be way too tight in another. Especially if it was set at the minimum in side of the range on the good spot.

75 for a while in an empty jeep isn't much load. Honestly 1 week in a lightweight jeep and the gears were blue and swapping metal. Doesn't really sound like a break in problem.
 

Steve

Bronco Guru
Joined
May 5, 2003
Messages
2,986
Loc.
Grand Junction, CO
Not that I doubt your skills, but that sounds more like a set up problem.

I've set up a helluva lot of gears, and that's the only set that have ever had problems of any kind. I check runout and I'm very picky on the pattern and backlash, as well as preload on both the carrier and pinion. Unless the setup changed after they were installed it wasn't a setup problem.

:shrug:
 

00gyrhed

Bronco Guru
Joined
Aug 3, 2006
Messages
2,428
Dude, didn't mean anything by it. I have put togehter 100's in my life. I have never broken one in on purpose. I might drive it 30 minutes and see if it is getting unusually hot, or that it makes noise, but never more than that. The only problems I have ever had was related to using old worn gear sets. sometimes you have to get creative to get them quiet.

I learned from my father who went through his greyhound apprenticiship in the 50's. They put them together pattered them and loaded them up with people and put them on the road. They kept records of every one they built and how long it lasted, so he knew what would last. His book has pictures of "acceptable" patterns that today would be called "unacceptable" in the magazine articles and on this forum. I believe the Ford Shop manuals From the late sixties have pictures of "acceptable patterns" that most experts would today reject. Over the road truckers do the same as do most fleet mechanics I have talked to. There isn't time or money to break in gear sets. They fix it and put it on the road. Never known anyone who raced to break one in. I will bet that 99% of front sets never get "broken in".

Sometimes things happen. Whats the old saying? If you do not ever screw up, you are probably not doing anything.

I put together a 9" for a buddy of mine in high school. (30 years ago) We though we had it good. Nice pattern, no runnout, perfect backlash. I did everythng the way I was taught. But, aparently a carrier bearing race did not get seated good. When he first started driving it, is seemd fine but it started making noise. We took it apart and the edges of the teeth were blue. Backlash was out of spec. The carrier had shifted.

I believe it is a good idea to take it easy on anything you rebuid until you know it will stay together. If the gear set is properly cut and you put it togehter right, it will stay together breakin or not.
 
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