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Gear Break-in tips?

marcusguy

NAXJA Forum User
Location
Jing Zhou, China
So I've read around the internet and here about how to break gears in (drive 20 minutes let cool...etc.), but my question is about what type of oil to use... if it matters at all. I know that with engines its best to use dino-oil for the first 3,000 or so, is there anything similar with gears or can I go ahead and slap some synthetic in there?

Also, I've got a couple of hunderd (about 300) on the front and about 150 on rear now doing the drive 20-30 and letting it cool till I drive again. I don't have to do that all the way to 500 do I? I need to take a road trip tonight and will be driving about 2 hours on the freeway and I am curious if you guys recommend me letting the diff cool throughout the trip or if it's ready to go the whole distance.

Marcus

The front seems great when I put it in... possibly quieter and smoother than the stock setup. The rear isn't making any noise (nothing I can't hear over my BFG A/Ts that is... meaning, it isn't making much if any), but I can feel more subtle vibrations than before... I'm assuming that's normal and it might get better with more miles?
 
You can make the road trip. Don't push it hard, avoid hard acceleration, and try to coast as much as possible (not out of gear, but just neutral throttle).
 
I dont completely agree with that,the most important thing is to not stay at 1 particular rpm.Try to go back/forth between speeds,city driving is the best for breaking in things!
 
Those new subtle vibrations MAY just be the result of your engine now spinning a little faster than you were used to.
 
Maybe overkill, but my routine went like this:

1. 15 min up on jackstands idling in 4th gear Note! stay in the Jeep in case it falls off ;) then cool for a half hour or so.

2. Repeat #1 and cool down

3. 50 mile -+ EASY drive, varying speeds and avoiding hard loads.

4. Drain dino oil out (yes, it'll be silvery) and replace.

I used Dino oil for #1-3, then refilled with M1 synthetic.

The front was done at the same time, but I didn't use 4WD for the 50 mile loop... We did Tellico a week after the install, and it got 'broke in' there I'm sure...if not, I had to drive the 350 mi home in front wheel drive, so it was by the end of that trip. After I unpacked but while the fluids were still warm, I drained the oil again and replaced.
 
my drive home from the dealer on the first day of life with my new xj was a 90 mile trip. i just varied my speeds every few minutes (5-10 min. intervals), and did my best to stay off any 'power' moves.
i drained the orriginal 'stuff' out at 308 miles, replaced it with the 'real thang' (mobile 1 that is) and never looked back. i also replaced the fluids in both differentials and the transmission with amzoil (another 'pure' synthetic).
by using synthetic early in your 'baby's' life, she'll break-in slower (it'll take more miles to actually get her broke-in), but it'll more than pay off in the long run... that is iffin' you plan on keepin' her for a while.
 
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