how to break in 4.10 gears on the front axle

Hello-

about to fit a new set of 4.10 nitro gears to replace my old worn out 2.4 gears.

of course -I know there is a break in period and i should be very careful about how i drive for 500 miles etc- but i wanted to know- should i do it in 4Wd?

I know the pinion gears on the front diff spin all the time even in 2wd- but i want to make sure the front diff gets a proper break in period-same as the 8.25 on the rear-so it will not fail when i will eventually go offroading when the break in period will be over.

p"s-

i have select trac so i can drive on the street in 4wd.

I didnt know you could change the gear ratio in the front. Did you change the transfer case gearing as well?

As far as breaking it in, IMO: drive as usual except no speeding or very long trips for a while.
Some will put a new axle in and forget about the rest! Just Drive it like they stole it!!

J33Pfan said:

I didnt know you could change the gear ratio in the front. Did you change the transfer case gearing as well?

As far as breaking it in, IMO: drive as usual except no speeding or very long trips for a while.
Some will put a new axle in and forget about the rest! Just Drive it like they stole it!!

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J33Pfan , Yes you can regear the front
No you do not have to change anything in the transfer case ( why would you ? )

tomer Break in, drive enough to warm up the gears, stop let them cool off , do it again etc No hard pulls , no long drives . I always put in 4x4 , then out etc

tommudd said:

J33Pfan , Yes you can regear the front
No you do not have to change anything in the transfer case ( why would you ? )

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I thought front & rear had to be matched up correctly to prevent issues.

wow look what Sirri found

NEW GEAR BREAK-IN PROCEDURE
New gear sets MUST be broken in correctly to prevent damage. Not following proper break-in procedures will lead to overloading and overheating the ring and pinion as well as breaking down and ruining the gear oil. Not following proper break-in procedures can be determined during inspection and will void the warranty.

Please follow the below guidelines to ensure a proper break-in and long life of your gears.
• Only use high quality gear oils. ECGS recommends Lucas non-synthetic 85W-140
• On initial run, drive lightly for 15 to 20 minutes then stop to allow differential to cool completely for 20 to 25 minutes.
• Avoid towing and heavy acceleration, as well as vary speeds every 5 to 10 minutes while driving on highways.
• Drive conservatively and do not drive more than 50 miles at a time without allowing a cool cycle during the first 500 miles following installation.
• After completing initial break-in, change gear oil at 500 miles. Small metal particles are normal and gear oil will typically be black. Excessive metal in gear oil should be reviewed by a competent differential mechanic to ensure safety of internal parts.

Post gear oil change and initial break-in: Towing.
• First time towing should be limited to light load for no more than 15 miles, then allow differential to cool completely for 20 to 25 minutes.
• Repeat this procedure for first 45 miles of towing for full break-in of gears for towing vehicles.

PREMATURE OVERLOADING AND IMPROPER BREAK-IN WILL CAUSE GEAR OIL BREAKDOWN AND MAY RESULT IN RING AND PINION FAILURE VOIDING THE GEAR WARRANTY!

https://eastcoastgearsupply.com/ft-1479-new-gear-break-in-procedure.html

https://www.youtube.com/watch?v=LeEttxH29sQ

J33Pfan said:

I thought front & rear had to be matched up correctly to prevent issues.

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Well, yeah.... the rear would need to be 4.10 ratio as well. But that has nothing to do with the transfer case.

OP has a 4cyl and already has 4.10s front and rear.

Just as i wrote- I know how to break the gears in. my question was should i do it in 4WD.

Anyway-thanx Tom i am gonna do it in 4WD just to make sure.

Stupid question but does this mean that all new KJs fresh off the assembly line went through this break-in procedure?

hadtomer said:

Hello-

about to fit a new set of 4.10 nitro gears to replace my old worn out 2.4 gears.

of course -I know there is a break in period and i should be very careful about how i drive for 500 miles etc- but i wanted to know- should i do it in 4Wd?

I know the pinion gears on the front diff spin all the time even in 2wd- but i want to make sure the front diff gets a proper break in period-same as the 8.25 on the rear-so it will not fail when i will eventually go offroading when the break in period will be over.

p"s-

i have select trac so i can drive on the street in 4wd.

Click to expand...

GREAT POST! And all the way from Israel!! :happy107:

Gotta Love this Forum!!! :winner_first_h4h:

J33Pfan said:

I thought front & rear had to be matched up correctly to prevent issues.

Click to expand...

Of course they do but has nothing to do with the transfer case, front and rear diffs have to be same gearing

Billwill said:

Stupid question but does this mean that all new KJs fresh off the assembly line went through this break-in procedure?

Click to expand...

No of course not, but the majority do not hook a fully loaded trailer to a brand new KJ , run over 5 hours before stopping like I did. But of course it did have almost a hundred miles on it by the time it was delivered to me. :happy175:

Every new car I have ever owned had the oil changed at 1,000 miles. (Then every 3,000 miles after that.)

I would do the same thing with a new differential, though not as often with the subsequent changes.