4x4 On Pavement-What Breaks?

Pitter, I don't believe anything breaks, UNLESS you have different diameter tires front & back, though you might not like the gas mileage. I've gotten your advice in owner's manuals, though, so it must do something. I've done it for over a hundred miles without realizing it was engaged with no apparant damage, so I doubt you've done any noticeable damage. Oh, and the same manuals do recommend engaging the 4WD for short drives on gravel or dirt, whether you need it or not.

Timber knows all about this stuff. So does farmerman, so I'll leave you to them.

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yeah....timber knows this stuff....

Unlikely any damage was done - a few miles of normal operation on dry pavement in 4WD shouldn't break anything. It'll use more fuel, and it'll increase front tire wear a bit, but as long as you weren't stressing the running gear with manuevers involving hard turns, abrupt accelleration/decelleration, jerky starts and stops, or very heavy load management, all should be fine. In 4WD, on or off pavement, steering and braking are affected, steering particularly, as you noticed in the parking lot. Manuevering in 4WD does particularly impact the front wheel locking mechanisms, and to a lesser extent the CV or U joints of the half-shafts, and lesser yet the planetaries in the transfer case, but as long as the stress isn't applied through sudden shock, and is not allowed to continue for many, many miles of dry pavement operation, your biggest inconveniences are gonna be increased fuel consumption (you're powering more rotating mass - the transfer case and the front drivetrain, which otherwise would be freewheeling - adding unnecessary drag and friction load to the engine's work requirement, and your power steering pump hasta work harder, further reducing fuel economy), increased tire wear, and less-than-optimal braking and handling. Don't worry about it, and just don't make a habit of doing it.

If anything were to break, most likely it would be the locking hubs. They're not that hard to replace (I've torn up more than a few - and replaced some "in the field" under really crappy conditions - rain, mud, cold, dark and a limited toolset can be real irritating, especially when all simultaneously in play ), easier, really, than doing a brake job. Electric, or "automatic" hubs, most likely what you've got, will be lots pricier than manul hubs. On the bright side, in most situations, manual hubs can be substituted for electrics, at around 1/3 to 1/4 the cost. Aftermarket hubs, both electric and manual, are available in various performance grades above manufacturor's OEM specs, and often will be priced similarly to factory original replacements. Frankly, though, unless hardcore off-roading is gonna be a major consideration, aftermarket heavy-duty/severe service/competition running gear is highly unlikely to offer any cost/benefit advantage.

Thanks for the good information. Actually I think the transfer case is always engaged with at least one of the drive shafts, not free wheeling unless you shift it into neutral to operate say a Power Take Off winch. I believe the drive goes from the engine to the tranny to the transfer case where it can then be directed to just the rear shaft or divided front and rear. (There was one design I saw years ago that had a single shaft to the rear but two shafts emanating from the the front of the transfer, one to each front wheel. Must have been invented by a u-joint manufacturer). My understanding is that the auto front hubs on the Dakota are locked/unlocked by vacuum. I also have an '06 Mazda 2600 (not imported to the US) which has electric hubs.

Yeah, the rear drive components of the transfer case will be engaged unless they an be selected out to drive a PTO, but unless 4WD is engaged, the front drive components, and the connected front drive running gear - the shafts and joints - will freewheel; they aren't powered. Thats why its recomended to engage 4WD once in a while if its not used regularly; keeps everything lubed up and fit. Its also good practice to pass through neutral into reverse and back up a couple dozen yards when disengaging from 4WD, whether you have manual or automatic hubs - that just makes sure everything fully disengages and reverts to 2WD. Oh, and in regard to "Shift on the fly" 4WD, its best to not go from 2WD into 4WD at much above 35-40 MPH; catching up to the rest of the truck and digging in to share the load can be a helluva shock to the front drivetrain, and even moreso if the truck is heavilly laden or pulling a hefty trailer.

Vacuum hubs or electric hubs, little functional difference apart from activation - and both are pricey.

How about 80 on the freeway on the rain in 4 hi, will that cause damage? I have a 91 Dakota 4wd v8. I would like to use 4hi whenever it rains but worried about breaking something as well...

I don't know about 80 mph but my understanding is that if there's any slippage at all, which there would be during rain on pavement you are safe using 4 hi.

@Racer156... Unless you have several thousand extra dollars to doll out to repair shops( worst case scenario )do not use your 4WD on anything besides going slow over dirt or rocks, any speed over ice, snow, mud, or sand [real slippage], and just take it easy and slow in rain... I'm dealing with possibly losing my SUV because I thought 4x4 would get me home safe 5 hrs through the rain. Well know I'm thinking totaling it would have been the better option only if no-one would've been hurt & my driving skills even with the hazards on and going much slower with 2 wheel drive would have caused me to do. That's just what I've gathered from some of the forums I skimmed through... + my drive train warranty is null and void due to missing the 5 yr inspection...