Gear Break in Period

CharlieK

Member
Does this sound right?
Picking my jeep up this afternoon, with my new 4.88 gears. Shop is telling me first 100 miles no more than 20 miles at a time let them cool, before the next 20 miles. Speed no greater than 45.
Next 400 keep speed under 55.
Next 500 keep speed under 70.
Change gear oil at 500-1000.
Can't use lockers until I reach 1000 miles
Not sure if it matters but front axel is PR 44 ARB locker/ rear is stock D44 with ARB.
 

cozdude

Guy with a Red 2-Door
Does this sound right?
Picking my jeep up this afternoon, with my new 4.88 gears. Shop is telling me first 100 miles no more than 20 miles at a time let them cool, before the next 20 miles. Speed no greater than 45.
Next 400 keep speed under 55.
Next 500 keep speed under 70.
Change gear oil at 500-1000.
Can't use lockers until I reach 1000 miles
Not sure if it matters but front axel is PR 44 ARB locker/ rear is stock D44 with ARB.

mine was a bit different.

there are 5 break-in periods of 20 miles or less. accelerate easy and no faster than 55mph! let gears/oil cool for at least 2 hours before you go out again. after the 5 break-in drives you can drive normal. after 500 miles follow eddies full rear diff service like your changing the diff cover (http://wayalife.com/showthread.php?7626-Heavy-Duty-Axle-Differential-Cover-Installation-Write-Up). after 500 miles you can go off road. i would wait to 1000 miles personally to off road and use locker just to be safe
 
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CharlieK

Member
Thanks for the link. What I've read was consistent with your break in. What struck me as odd was the the max speed, they suggested.
 

cozdude

Guy with a Red 2-Door
Thanks for the link. What I've read was consistent with your break in. What struck me as odd was the the max speed, they suggested.

yea for the first 5 break in's i was suggest no faster than 55 but after that it didnt matter. i have editied it now so it reflets in my original post
 

BumpStick

New member
I'm going to be regearing my JK soon. It's my toy and rarely gets driven. About the only time I take it out is to go wheeling. I'm getting f&r Detroit lockers installed too. If I'm only running mud do I really need to wait that long to go wheeling?
 

Skirmish

New member
You can go off road as soon as you like. The concern is overheating the gears while they conform to each other. If you run higher speeds for a long period when they are new the heat will damage the gears. They are strong enough to run off road straight out of the shop but they need to be worn a bit to settle down the friction.

Avoid the highway for more than 20 min in the first 500 miles and you'll be fine. If you do a stretch at 65, put you hand on the diff cover and you will feel the heat.

Sent from my HTC One using WAYALIFE mobile app
 

BumpStick

New member
OK so the concern isn't mileage/time driven, it's the heat?

Does anyone know the number and duration of the heat cycles that are need for proper break in?
 

Skirmish

New member
It isn't about heat cycles. It is about wearing metal against metal till it is smooth and not overheating. New gears need to mate and until that happens they rub which causes friction which causes heat. Too much heat warps metal and that is bad. If your diff cover isn't red hot you are fine.

Sent from my HTC One using WAYALIFE mobile app
 

cozdude

Guy with a Red 2-Door
It isn't about heat cycles. It is about wearing metal against metal till it is smooth and not overheating. New gears need to mate and until that happens they rub which causes friction which causes heat. Too much heat warps metal and that is bad. If your diff cover isn't red hot you are fine.

Sent from my HTC One using WAYALIFE mobile app

it is actually about heat cycles. the heating and wearing of the metal on metal strengthens the two while it is getting smooth. that is why they say to do 5 break ins or 5 heat cycles of no more than 20 miles. Yes the heat can cause the metal to warp so allowing proper cooling of the gears and oil will help prevent it. i wouldnt go off-roading untill you hit the 500 mile mark. proper break in will strengthen the gears even more so then they are out of the box
 

cozdude

Guy with a Red 2-Door
mine was a bit different.

there are 5 break-in periods of 20 miles or less. accelerate easy and no faster than 55mph! let gears/oil cool for at least 2 hours before you go out again. after the 5 break-in drives you can drive normal. after 500 miles follow eddies full rear diff service like your changing the diff cover (http://wayalife.com/showthread.php?7626-Heavy-Duty-Axle-Differential-Cover-Installation-Write-Up). after 500 miles you can go off road. i would wait to 1000 miles personally to off road and use locker just to be safe

OK so the concern isn't mileage/time driven, it's the heat?

Does anyone know the number and duration of the heat cycles that are need for proper break in?

see my original post above. there are 5 inital break in/heat cycles you need to do with your gears.
 

Skirmish

New member
it is actually about heat cycles. the heating and wearing of the metal on metal strengthens the two while it is getting smooth. that is why they say to do 5 break ins or 5 heat cycles of no more than 20 miles. Yes the heat can cause the metal to warp so allowing proper cooling of the gears and oil will help prevent it. i wouldnt go off-roading untill you hit the 500 mile mark. proper break in will strengthen the gears even more so then they are out of the box

Actually the heating and cooling would make them brittle but that is just science. The strength is already there and if you are in charge of annealing your gears I would find a company that knows more about steel.

Sent from my HTC One using WAYALIFE mobile app
 

cozdude

Guy with a Red 2-Door
Actually the heating and cooling would make them brittle but that is just science. The strength is already there and if you are in charge of annealing your gears I would find a company that knows more about steel.

Sent from my HTC One using WAYALIFE mobile app

i guess then we need to find a new company not in korea then since all the gears are made there and just thrown in different boxes for different companies lol
 

Skirmish

New member
i guess then we need to find a new company not in korea then since all the gears are made there and just thrown in different boxes for different companies lol

I guess you need to lol what ever company you find cause steel reacts the same. The more you heat it the more brittle it gets. Lol

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jeeeep

Hooked
been driving jeeps and other cars that have had gear swaps, don't recall ever doing such and extensive break in.

my break in procedure:

after install keep it under 55, stop after 15-20 minutes to allow the diff to cool - 15 minutes should be ample time

after the initial cool down, for the first total of 500 miles kept it under 60

put at least 500 miles on the gears before towing or heavy use (4x4),

I changed the oil at 500, did towing break in procedure then changed the oil again at 1000

towing on a set of new gears requires more cooling periods. when doing the 1st tow, during the 1st 50 miles it was 15/15 drive 15 miles, let it cool 15 miles after that it's all good.

I have over 80k miles on my gears and also tow with no issues.

The front was recently swapped to a PR44 and the gears looked great.
 

JK_Dave

Caught the Bug
Actually the heating and cooling would make them brittle but that is just science. The strength is already there and if you are in charge of annealing your gears I would find a company that knows more about steel.

Sent from my HTC One using WAYALIFE mobile app

The process of heating and cooling could make a metal brittle, but I think that depends on the type of metal and the rate it is heated and then cooled. I think what Coz was getting at was the process of stress relieving, which I'm guessing you already know, but for the sake of everyone else is accomplished by heating a metal below the lower critical temperature and then cooling uniformly.
 

CharlieK

Member
yea for the first 5 break in's i was suggest no faster than 55 but after that it didnt matter. i have editied it now so it reflets in my original post

Coz, thanks the help hit my 500 today. Gonna use WAL right do my change and should be good to go from there.
 

NAUJK

New member
If all goes well this week I will be pulling the trigger on a new PR44 front with 4.88 gears and then will need to regear the rear. I am already nervous enough spending that money on a PR44, ive also been nervous for the break in period. I dont want to mess up my gears. This thread and the thread I made cus I couldnt find this one helped a lot. Thanks everyone!

:fingerscrossed: Everything goes well and I can order the PR and get everything ready for this big change!
 
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