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Finally getting 4.88 gears, but how do you go about breaking in the front diff?

Glad_he_ate

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I forget about the 4 auto as itā€™s not an option for us oil burners lol wifeā€™s 4xe has it and she likes it.
 
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XraytecH

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Sorry if my question smells of NOOB. Iā€™m just trying to build a knowledge base. This is the first vehicle where Iā€™ve done most of the work but gears Iā€™m leaving to the pros. Ring & Pinion change as everyone knows is a huge investment of time/money and I wanna break them in right.

Conventional wisdoms seems to dictate, or at least what Google saysā€¦

  • After light use for the first 15-20 miles, stop and let the differential cool before proceeding any further.
    • Repeat this process two or three times.
    • The gears run hotter than normal during the break-in process and require two or three heat-cycles to ensure proper performance and life expectancy.
  • Avoid heavy acceleration and don't do any towingduring the first 500 miles.
    • If you plan to do any towing following the initial 500 miles, then tow for a short distance (about 15 miles) and then stop to let the differential cool for 10-15 mins. Then resume your trip as planned.
    • If you've already put in over 1,000 miles on the new differential, then the diff is already broken in. Feel free to tow as normal.
  • We highly recommend changing the oil after the first 500 miles. This will remove any metal particles or phosphorus coating that has come from the new gear set and bearings.

Great!!! Now let me elaborate on my original question.

So am I to assume that the front ring and pinion gear are always engaged even in 2 wheel drive. If yes then this thread ends here, Iā€™ll just follow the above break in procedure. If no then back to my original questionā€¦

ā€œHow do I go about breaking in the front diff. Do I simply run my JT in 4Hi for the next 500 miles?ā€
 

WILDHOBO

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iā€™ve always thought that was odd too. Off the lot we donā€™t think about it šŸ¤£
As I understand it, the aftermarket gears have a tighter tolerance, so break in is more important.
 

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WILDHOBO

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Sorry if my question smells of NOOB. Iā€™m just trying to build a knowledge base. This is the first vehicle where Iā€™ve done most of the work but gears Iā€™m leaving to the pros. Ring & Pinion change as everyone knows is a huge investment of time/money and I wanna break them in right.

Conventional wisdoms seems to dictate, or at least what Google saysā€¦

  • After light use for the first 15-20 miles, stop and let the differential cool before proceeding any further.
    • Repeat this process two or three times.
    • The gears run hotter than normal during the break-in process and require two or three heat-cycles to ensure proper performance and life expectancy.
  • Avoid heavy acceleration and don't do any towingduring the first 500 miles.
    • If you plan to do any towing following the initial 500 miles, then tow for a short distance (about 15 miles) and then stop to let the differential cool for 10-15 mins. Then resume your trip as planned.
    • If you've already put in over 1,000 miles on the new differential, then the diff is already broken in. Feel free to tow as normal.
  • We highly recommend changing the oil after the first 500 miles. This will remove any metal particles or phosphorus coating that has come from the new gear set and bearings.

Great!!! Now let me elaborate on my original question.

So am I to assume that the front ring and pinion gear are always engaged even in 2 wheel drive. If yes then this thread ends here, Iā€™ll just follow the above break in procedure. If no then back to my original questionā€¦

ā€œHow do I go about breaking in the front diff. Do I simply run my JT in 4Hi for the next 500 miles?ā€
Do you have 4 hi auto in your JT?
 

Glad_he_ate

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Do you have 4hi auto as an option?? If not then DO NOT run in 4 hi on pavement or you WILL FUCK SHIT UP!! If you HAVE 4 auto then there is no reason not to use 4hi Auto to spin the pinion and ring to aid in brake in. Your other option is to run it off road as much as possible and or run it in the snow belt in winter ??
 
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XraytecH

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Thanks Folks!!!

Found my answer. But please continue the conversation in this thread so that others can benefit.
 

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Then the answer is leave it in that mode throughout the whole break in. 2wd wonā€™t turn the front drive shaft. But it wonā€™t hurt anything to use actual 4hi on a dirt road when you have the opportunity. Otherwise 4hi auto. Just donā€™t shift in and out of 4hi auto faster than 45mph or so. You can drive it as fast as you want once itā€™s in that mode.
 

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WILDHOBO

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Then the answer is leave it in that mode throughout the whole break in. 2wd wonā€™t turn the front drive shaft. But it wonā€™t hurt anything to use actual 4hi on a dirt road when you have the opportunity. Otherwise 4hi auto. Just donā€™t shift in and out of 4hi auto faster than 45mph or so. You can drive it as fast as you want once itā€™s in that mode.
And for what itā€™s worth, the shop that did mine used non LSD compatible fluid for the break in period. Therefore, lockers should not be used. After break in was done, they put in proper expensive fluid and lockers were ok to use again.
 

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The same way we break them in when new from the factory? Seriously, Iā€™ve wondered why there are break-in procedures for new aftermarket gears, but not new production gears.
I've wondered that too. I know that Jeep doesn't run the ring and pinions to "break them in", and the manual just says "less than 55 mph first 60 miles" and be careful (paraphrase) for the first 300 miles and relatively hard acceleration periodically. If I ever get my JTR (built waiting to ship), I'll put 4.56 or 4.88 Spicers in, the same manufacture as the stock 4.10s, so should I just stay under 55 for the first 60 miles etc.? Maybe the ring and pinion guys are just cautious.
 

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And for what itā€™s worth, the shop that did mine used non LSD compatible fluid for the break in period. Therefore, lockers should not be used. After break in was done, they put in proper expensive fluid and lockers were ok to use again.
Selectable lockers (electric or air actuated) donā€™t use special fluidā€¦
 

Geoarch

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Exactly. When my 5.13ā€™s went in, they called for a 1000 mile break in. First 100 miles under 45mph, the remaining 900 miles under 65mph. I ran the entire 1000 miles in 4high auto to rotate the pinion, but not the axles unless there was slip. Always varying speeds and never using cruise control.
That doesn't help someone who doesn't have that transfer case, it I understand correctly.
 

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That doesn't help someone who doesn't have that transfer case, it I understand correctly.
True, but the OP does.
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