Front Gears breaking in (1 Viewer)

[AlexJet]

Just swapped a new set of gears on my FJ40.
Now they need to break-in. As usual I need to make ~20-25 short trips of around 25km (15mi) each to let them warm up while driving and then slowly cool down for at least 15-20 minutes.
The rear is very simple, just driving it. The question come for the front.
In normal 2WD condition only rear gears are rotated as front driveshaft is disengaged in the Transfer Case and not rotating. If I do switch to 4HI only, it will rotate the front driveshaft, would it? In this case front gears will be rotating, but without any load. Would it be sufficient for breaking-in or do I need to load them up?
FJ40 has a part time 4WD system which means I can't use it on dry asphalt. If I do engage the hubs and my understanding both have to be engaged as only 1 would not do the trick, I can only drive on a straight line and no turns.
So, what is the best way and the right way to break the front gears in???

 

[savasdf]

Hi,

Thats something I'm going to have to soon on my BJ40, to answer your question just by engaging 4WH should be enough of a load to break them in but you might just add a few more miles than what you are doing to the rear.

When locking the hubs, you are correct by having to lock both, else you are not doing anything, but you can still turn the wheel while the hubs are locked you just need to put more effort into the turning if the wheel but never lock the hubs and drive on a Tarred road, you will do damage to the hubs and possibly the Axles. Locking of hubs is strictly for Offroad and tricky situations not too be used when not needed. As long as speeds are low you can use them Offroad only!

Have fun and good luck.

Sava

 

[AlexJet]

I know that locked hubs and 4WD (high or Low) in Part-Time 4WD system (which is on Land Cruiser) is not for non-slippery surface as when you start turning your wheels run different distance opposes to straight line driving when covered distance by each wheel is the same. So it's not that of a question of how hard to turn the wheels, it's more a question of putting allot of stress and loads on drivetrain components. This why I was thinking to find a long street in a country side, something like 10-20km of a straight line and lock the hubs there, then unlock, turn around, lock again and drive back. This should work too.
But if just leaving hubs unlock and engage 4WD High with a shifter actually brings enough load to break them in, then I'll do it and drive all the time like that for the first 500-600km (~310-375mi).

 

[zebrabeefj40]

Remove the rear driveshaft and drive around in 4H with the hubs locked. Yes, you can do that without damage including highway speeds. Then the front diff will be broken in just like the rear diff.

Nick

 

[camcruiser13]

over rated

lets be honest

who really breaks their gears in

drive around in 4 wheel drive for a day, then change your gear oil and call it a day

 

[AlexJet]

Allot of people actually do break their gears in.
Aftermarket gears need to be broken in as they are not made to the OEM tolerance, would cost manufacture too much while quantities are significaly less then OEM.
Because of this they heat up allot during first 1k and need to be cooled.
You don't need to break in original gears when you buy a new vehicle.

 

[AlexJet]

Remove the rear driveshaft and drive around in 4H with the hubs locked. Yes, you can do that without damage including highway speeds. Then the front diff will be broken in just like the rear diff.

Nick

No good as I need to break in both front and rear.

 

[cjgoode]

Even driving in a straight line on pavement with hub locked and in 4wd would put your drive train at serious risk. First you cannot drive in a perfect straight line, second your tires will not be the exact same size. Will not take much over a distance to start really binding up. I would never drive more then a few feet on hard payment in 4wd.

 

[amaurer]

As you say, you've got a part time 4wd system, so you should ask yourself does it really matter if the front gets broken in?? Gear break-in isn't going to do anything for you when all you're doing is crawling over rocks with that axle a couple times a year.

If you really MUST break them in, then do as was mentioned and break in the rears, then remove the rear DS and break in the front.

But seriously...?? The front is driving on the coast side of the ring gear anyway, so clearly Mr. Toyota had a "no big deal" attitude and so should you.

 

[AlexJet]

I use extensively 4WD when off-roading. The terrain here in Eastern Canada is consist of heavy forested areas with allot of mud and small rocks all over the places. It's a bit different then in Sates, especially on the West.

Well, I just put it into 4WD with unlocked hubs and drive like that...

 

[amaurer]

I use extensively 4WD when off-roading. The terrain here in Eastern Canada is consist of heavy forested areas with allot of mud and small rocks all over the places. It's a bit different then in Sates, especially on the West.

What does that have to do with anything? When you're "offroading" there are you driving 300 miles at a time at 100kph in 4HI?

... if not, then its not going to matter.

 

[cruiserjunkie]

Just swap your diffs front to rear after you break in the current rear gears

 

[AlexJet]

Just swap your diffs front to rear after you break in the current rear gears

Interesting idea if you have the same 3rds.
I'd stay with basic idea. My rear is Detroit locked.

 

[cruiserjunkie]

Interesting idea if you have the same 3rds.
I'd stay with basic idea. My rear is Detroit locked.

Still work just swap back after break in. Only three times the work . Just lock one hub it will turn the ring gear

 

[Kris]

Alexjet,
I agree with your statement about different stresses when the hubs are both engaged when you are referring to a full-time engaged locker like a Detroit or a spool. If you have open differentials, then driving around with the hubs locked in isn't going to cause anything disastrous. Granted, if you leave them locked all the time, it will cause added wear on bearing etc from spinning. The idea behind open differentials is the ability to have 4x4 engaged and not have to worry about causing stress on components. Even with a full-time locker and hubs engaged, with common sense, the stress that is put on the system isn't going to be enough to break something.

Long story short, lock your hubs in and drive around in 4x4.

 

[zebrabeefj40]

Alexjet,
I agree with your statement about different stresses when the hubs are both engaged when you are referring to a full-time engaged locker like a Detroit or a spool. If you have open differentials, then driving around with the hubs locked in isn't going to cause anything disastrous. Granted, if you leave them locked all the time, it will cause added wear on bearing etc from spinning. The idea behind open differentials is the ability to have 4x4 engaged and not have to worry about causing stress on components. Even with a full-time locker and hubs engaged, with common sense, the stress that is put on the system isn't going to be enough to break something.

Long story short, lock your hubs in and drive around in 4x4.

This will not end well... Driving around with the hubs locked in 4x4, open diffs or not, on high traction surfaces like pavement or dry gravel will bind up and break driveline parts.

Nick

 

[LT]

The front end does not see nearly as much stress as the rear therefore trying to have a "break in" period for your front diff isn't really necessary. Considering you aren't doing sustained highway speeds to really get your gears hot in the front it is a mute point. The gears in my FJ40 and our FZJ80 have had zero break in and we wheel the piss out of our trucks with no failures due to a bad break in.

 

[Weber Sarge]

With no central diff in the transfer case, running in 4hi on hard pavement can cause binding and will hurt stuff . I've done it by accident with no immediate issues but it's just not a good idea . If you really want to break in a front gearset you can either drive at highway speed in 4hi on a gravel road for 20 minutes or just remove the rear driveshaft . Be aware that sometimes due to different axle lengths in a front diff or locker they can steer themselves during gear changes, sometimes nearly changing lanes...
Sarge