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Discussion Starter · #1 ·
Hello,
I have done tons of research, but have not found a solid answer on how to break in gears. I understand the importance of the heat cycles, it makes total sense to me. How does one break in both front and rear if it is a death sentence to use 4Hi on the streets? I have a Dana 44 rear with thick cut gears and a D30 up front, both at 4.56. If I cannot get a proper load on the front R&P at the same rate as the rear what should I expect?
Ironic as when I need four wheel function I will be gassing hard, but yet my tiny D30 will not be up to speed as far as break in mileage. I would be hard pressed to understand how a D60 on the front could equal a D44 if the gears are not broken in properly? Yes I know the size matters, I am talking hypothetical. If certain gears are not "run in" they will fail.
Please gear guru's chime in, I have a toy that is begging me to slap her ass and call her by the wrong name to see if I can hold on lol.
 

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heheh, did the factory break in the gears before handing the jeep over to the 1st owner?
Did the 1st owner break in the gears like you want to now?
I always wondered this and I have built many a engine. I know that the cam needs run in time to keep from wiping the lobes. But after that, run it like you stole it.
Just change the oil after your first get away..
 

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I asked this question when I did my 1st re gear. My installer (ECGS) told me to not worry about the front. This is due to the front will never ever see the same stress as the rear as far as heat build up and strain. After my break in period they did not even check the front diff.

At least two other installers told me the same thing. (4WheelParts and Blalock Automotive)
Break the rear in...
 

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The ring & pinion shop that I use (West Coast Differentials) has always recommended the same break in procedure for front and rear regears even though the front isn't loaded when in 2wd. Several short drives (20 miles or so) to get them heated followed by cool downs, no towing or 4-wheeling for the first 500 miles, and change the gear oil at 500 miles. I've followed this on mine after several regears and have never had an issue.
 

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I ran in 4x4 on the road to break in the front and create heat. Then simply put back in 2wd. The argument that dry roads kill 4wd is BS! When I'm aired down to 5psi, LOCKED and crawling over rocks there is SIGNIFICANTLY more rolling resistance than doing 55mph on a highway in 4wd! . And guess what... my 4wd system works just fine and has not blown up. If Jeeps were really that fragile would they sell like they do??
 

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I ran in 4x4 on the road to break in the front and create heat. Then simply put back in 2wd. The argument that dry roads kill 4wd is BS! When I'm aired down to 5psi, LOCKED and crawling over rocks there is SIGNIFICANTLY more rolling resistance than doing 55mph on a highway in 4wd! . And guess what... my 4wd system works just fine and has not blown up. If Jeeps were really that fragile would they sell like they do??
Agreed! Run it down the highway in 4 hi. As long as you are going fairly straight, you aren't hurting anything. It's when you are in 4x4 on a hard surface and turning that your wheels are bound up trying to go diferant speeds.
 

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I ran in 4x4 on the road to break in the front and create heat. Then simply put back in 2wd. The argument that dry roads kill 4wd is BS! When I'm aired down to 5psi, LOCKED and crawling over rocks there is SIGNIFICANTLY more rolling resistance than doing 55mph on a highway in 4wd! . And guess what... my 4wd system works just fine and has not blown up. If Jeeps were really that fragile would they sell like they do??
I just had my Re-gear done last Friday. I'm about 250 miles in. Fluid change at 500 miles. Am I too late to run in 4WD for a bit?

Thanks in advance to the advice.
 

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I just had my Re-gear done last Friday. I'm about 250 miles in. Fluid change at 500 miles. Am I too late to run in 4WD for a bit? Thanks in advance to the advice.
Not at all, it's about creating heat cycles. My shop wanted 750-1000 miles before changing fluid and wheeling...
 

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Not at all, it's about creating heat cycles. My shop wanted 750-1000 miles before changing fluid and wheeling...
Thanks. I'll run it that way for a bit. I expect that going over 500 miles before changing fluid isn't too critical.
 

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You do not need to be in 4wd. The front gears on a TJ turn all the time even when not in 4wd.
 
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