Topic: Front Diff gear break-in? Drive it in 4Hi with hubs unlocked?

[TokTokE]

Hey all,

I'm trying to figure out the best way to put the necessary miles on my front Diff gears to get them broken in. 

Here's the catch:

Shouldn't drive with front engaged on asphalt, but also no real off-roading allowed during break-in.  I assume that means my option is easy dirt road driving.  500-1000 miles is a lot of easy dirt road driving if it's not something you normally do. 

So I'm thinking, what if I unlock my front hubs and drive normal slow city with 4Hi engaged and follow the normal break-in procedure as it would be for the rear? 
That way the front diff is still getting the friction it needs to heat cycle/wear in but the wheels are spinning free so no tire wear/drivetrain strain from the 4wd.   The only issue I see with that is that the front gears wont be loaded with the pull of the car, so that may affect the way it breaks in, but not sure if that's a concern or not. 

Crazy idea or reasonable?  If crazy, any other suggestions to make the front break-in less of a slog?

[OVRAROK]

http://performanceunlimited.com/documents/gearbreakin.html

[TokTokE [OP]]

Hell yeah!  Thanks for confirming for me

[blackdiamond]

I’ll add my two cents on this. The primary purpose of the gear break-in is to allow the two gears to “mesh” without overheating them which can damage the gears. I don’t see this as a significant concern for a front differential in a 2wd rig that’ll only be in 4wd while going relatively slow off road.  Just keep an eye on the temperature. A rule of thumb that I’ve heard is if you can put your hand on it you’re doing ok.

[Cheesemaker]

This makes me think, brand new vehicles off the lot.  They don't tell you about break in procedures.  Do they break them in at factory?    

[Gnarly4X]

This topic has been circumcised a good number of times.

In 20+ years of wheeling I don’t remember any wheeling buddy saying “Oh… I gotta break in my new diff gears.”

I know plenty of guys who installed new R&Ps, lockers, etc.

Are there millions and millions of vehicles manufactured, purchased and driven WITHOUT a “break-in”?

I realize gear manufacturers require/recommend a “break-in”. I don’t believe the recommendation has anything to do with requiring the mating surfaces to get happy.  It is xxx times more likely to have premature failure due to improper installation, actual gear defects, lack of maintenance, neglect (deep water crossing and don’t change gear oil). The Break-In recommendation is a standard “warranty stipulation” thing.

In a front diff, for the average 4-wheeler, running on a trail all day (Rubicon), how much heat could those gears generate?

“The suggested break in procedure is as follows, The first drive with the new ring and pinion should be under normal driving conditions (No hard starts, No racing, No off-roading, No towing and not at Highway speeds). The vehicle should be driven 15-20 minutes around town, normal stop and go driving.”

I have never known anyone who did this to "break-in" a new set of R&Ps, but I'm sure someone has.

https://www.revolutiongear.com/ring_and_pinion_break_procedure

If I were installing a new set of R&Ps I’d buy Yukon and buy their “no-questions asked lifetime warranty coverage”  Extended Warranty for $49.89.

For a tow vehicle like a new Dodge RAM 3500, Dodge does recommend a 500-mile break-in before towing.  That makes sense on a vehicle that can tow 37,000 lbs.

Gnarls.

[mudmaster]

I break the front diff in on the first trail ride.

[toyodaaddict]

I’ll add my two cents on this. The primary purpose of the gear break-in is to allow the two gears to “mesh” without overheating them which can damage the gears. I don’t see this as a significant concern for a front differential in a 2wd rig that’ll only be in 4wd while going relatively slow off road.  Just keep an eye on the temperature. A rule of thumb that I’ve heard is if you can put your hand on it you’re doing ok.

I agree with this.

Anyone who has dealt with new gears knows they run hot until broke in. Running them too long or too hard on break in can cause the oil to break down and not do its job. I always take care to properly break in a rear diff. For the front, I'll make a few gravel road drives in 4HI. After 50-100 miles dump the oil. Run some trails, dump the oil and forget about it.

[Gnarly4X]

Except for cross-country Mexico and the Glamis dunes, the rockcrawling and trails I ran were mostly are 1 mile or less. Rubicon is what 15? and Ducy-Ershim is what 31 miles?

At the recommended break-in it would take 500+ trail runs to break in my front diff.  At about 2 trail runs a month or about 24 times a year... hmmm.. I'd be really old by the time my front diff was broken in!!

Gnarls.

[TokTokE [OP]]

hmmm.. I'd be really old by the time my front diff was broken in!!

My thoughts exactly! 

I appreciate the insights, guys.   Looks like I'll be hitting the trails sooner than expected!  Cheers 

[Gnarly4X]

To beat this up just a tad more…. 

I often read anecdotal opinion, conjecture, and misinformation, with a few facts sprinkled around.

Here’s my anecdotal pomp n’ stink… 

“Just keep an eye on the temperature. A rule of thumb that I’ve heard is if you can put your hand on it you’re doing ok."

Without a Differential Temperature gauge how to do “keep your eye on the temperature”?

The temperature on a diff will normally run about 200d F. Human flesh will burn at first-degree at 118d F.  At 162d F human tissue is destroyed on contact. At 200d F you’d sustain a painful burn to the hand in about 1 second.

Without a temperature gauge, you don’t know what temperature the diff gear oil is at.

An AutoMeter Differential Temperature gauge is about $75.00.  If I ever change my R&P gears, I will definitely install one just to satisfy my curiosity.

Common, very slow, 4-wheeling we do like rockcrawling (All-day on the Rubicon at 2 miles per hour), most likely could not get the diff oil to "hot", so a breakdown of gear oil due to excessive heat is unlikely whether it is a new set of gears or at 50,000 miles.

This is the best information I’ve seen on the topic of differential gear oil.

https://eastcoastgearsupply.com/files/PDF%20Files/ecgs-gear-oil-recommendation1.pdf

Obviously breaking-in new gears by a recommended procedure can’t hurt anything.

For my past 4-wheeling activity, breaking in a set a gears by taking the time and calculating the miles and replacing gear oil would be way too painful for me.

However, again, now after 36 years of being involved in the off-roading and 4-wheeling hobby I have not personally witnessed anyone that does the recommended differential break-ins or has described a differential failure due to overheating or premature wear.

If I bought a $70,000 Dodge Ram 3500 for towing a boat or 5-wheel, and Dodge recommends 500 miles before towing, I’d most likely do what the factory manual recommends.  And
just to comply with any warranty requirements, I’d take it into the dealer and let them change the differ oil and record the mileage for the record.

Gnarls.