Why not just leave it in 4A for daily?

[Mystic]

At the risk of hijacking this thread, I've been wondering about drive modes for off-road.

Both off road mode and Baja mode have the rear diff locked by default. But I read that locking diffs are stressed except in very loose terrain.

What mode is best to use for flying around on dirt, rocky, and variable roads (as opposed to sand etc).

Honestly, probably 4A/4H or 2H. Assuming you basically mean "forest service roads" there's really no need for any kind of 4WD 99.99% of the time. Recommend cycling to the correct (most comfortable) suspension setting and just have fun and let it rip in a regular drive mode.

Or just cycle over to Baja and turn the diff locker off. I think you can change the auto-locking in those drive modes through FORSCAN, but I haven't yet done that.

Anyway, long story short, you don't need diff lockers for this kind of work. Diff lock mostly is for climbing big rocks, steep grades, or off-camber sections where you're lifting a tire.

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[Sparkherd]

They DON'T!!

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[Lion77]

Using a locked diff on-road can cause failure of the diff locking mechanism. Definitely a no no in dry onroad conditions.

Same thing with 4H on road in dry. Front and rear are mechanically locked together but becuase the front and rear tires wear at different rates, theres a small difference in diameter, so it creates binding in the T-case.

Off road or on dirt or gravel roads, theres plenty of tire slippage so theres no drivetrain issues and you can maximize traction.

Thats why Ford created a 4A transfer case, to give you rear biased AWD for on-road. Normally the front is freewheeling, but the electronic clutch engages like the torque lock in your transmission as soon as the PCM detects a difference in wheel speed between front and rear. Fords 4A is really seamless, id say it is as good as my wifes CX-50 which we just got (2026).

I would make the argument that using 4A on dry roads should not cause any additional wear becuase the clutch pack isnt engaging if the wheels aren't slipping, so its still just free wheeling. But there are some parasitic losses becuase additional gears are engaged in the TC, so it does affect fuel economy a small amount.

At the end of the day, I use 4A any time it rains or snows or if the roads are very twisty becuase I can rocket out of corners much faster with 4A and not break loose the inside rear tire.

Ford also automatically engages 4A in tow mode for added stability. But for jist driving around town, highway cruising and sport mode on back country roads which around here are mostly big long straightaway, it leave it in 2WD.

I use 4H off-road obviously, any dirt roads, gravel roads, farm fields, sand and trails. I used 4L one time when crawling up a rock face on a trail that ran about 25 feet (very steep uphill rock hill) and it worked awesome.

There was an old Jeep Cherokee (90s) on 40" tires that struggled for traction up that rock face and my raptor crawled right up it.

He had mega ground clearance with those huge tires and lift, but the older tires and compound were not biting well and the sheer size just wasnt the right thing for that situation, I dont believe it had 4L either so he was struggling to modulate the throttle.

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