This is my first SUV, so first 4wd vehicle and I'm still getting used to everything and learning stuff... so this question may sound stupid, but I haven't seen it covered in a search so I'll go ahead and ask..
..Is it bad on the drivetrain to use 4hi in the rain? The other day it was coming down pretty hard here and I found I had much better traction on the flooded (and just plain wet) roads in 4 wheel drive.

If you are on pavement, don't do it. There is not enough wheel slippage. You see, the part time 4 wheel drive systems, the front axle has a slight higher gear ratio than the rear does and this needs wheel slippage as not to "BIND" your drive line parts.

Read this to find out how it all works, will help understand it.

Um, no. There is no difference in the front and rear gear ratios. The binding occurs only when turning right or left; when the front and rear wheels are turning at a different speed.

But no, unless it's really slippery you shouldn't have the truck in 4WD... unless you never plan on turning.

If the road is completely saturated it's OK. Just don't make any tight turns with 4WD engaged. Water on the road is enough slippage for normal driving at reasonable speeds and without tight turns. Really though, you shouldn't even need 4WD on wet roads. If you do then you are either driving too fast for conditions or just need to spend some time getting use to how your truck handles, especially if you are new to trucks and rear wheel drive. Also, if you have the General Grabber or BFG Long Trail tires you may want to dump them for something better. Neither of those tires are too hot in the rain.

got rid of my x and now have a 02 toyota d/c. both vehicles have essentially the same type of 4wd systems. this is stated in my toyota owners manual. use h4 for normal driving on wet,icy or snow covered roads, this provides greater traction than two wheel drive, also you should drive in four wheel drive at least ten miles a month to lubricate the front components.

?!? Is this true? 10 miles?

for toyota anyways- its in my owners manual.

Actually, it's a good habit to get into. If you don't use 4WD often enough, say winter to winter, the system sits unused for 8-10 months. By running it once a month (and by that I mean getting everything up to normal operating temperature) you are helping to keep everything lubricated. Some people swear by it, others don't believe it.

You don't have to drive in 4WD to get the job done, just drive with the hubs locked. On the X, it's just a matter of starting your trip by shifting to 4hi as you pull away and then shifting right back to 2hi and leaving it there. Hubs will stay locked and everything will keep spinning without requiring you to stay on dirt etc. Not that staying on dirt wouldn't be preferred

Brent

Brent

This may sound silly but if you have the auto locking hubs can you still put it into 2hi and have the hubs stay locked without putting it into reverse? And how would I know if the hubs are still locked? Does it feel different or is it just that the light stays on? On a couple of
x-cursions I have seen other members do the reverse thing and I'm not sure if I need to. Thanks in advance.

If you've started driving in 4(hi/lo) with auto locking hubs, and you shift to 2wd, the hubs will remain locked until you've reversed direction.

There's really no indication that your hubs are locked. You don't feel anything, though gas mileage will be a bit worse. There is no indicator that the hubs are locked.

Actually with the radio down I can hear the front diff whine slightly when the hubs are locked. A good indication they are locked. And yes for auto locking hubs going in the opposite direction in which you locked them in is needed to unlock them once back in 2wd.

when you reverse listen for the click

Well I checked for this "click" when reversing direction tonight in the back alley (after returning to 2wd), and lo and behold, it was (just) noticable. Never noticed it before.

I've never noticed the whine on the highway if the hubs are engaged, but I'll have to listen for it in the future. Thanks for the pointers from more observant people...

Dave

not to beat a dead horse, but the nissan owners manual for the 4wd x says to use 4hi on wet roads. that being said, if one were to use 4wd as suggested in the manual and it caused problems, wouldnt nissan therefore be responsible since they gave that advice?

Well, that's a bit out of context. It says: (4WD, high range) Four wheels are driven. Use on roads where it is difficult to drive in the 2H position (i.e., driving at normal speeds on snow covered, icy, wet, muddy or sandy roads).

So while it does say "wet", it also says "difficult to drive in 2H".

I find it very difficult to drive when I'm too high.

Regardless, I wouldn't risk it. I've 3 jeeps and my X, and I would not do it unless I had full-time four whell drive (cause that's what it's designed for). I have had great success replacing my tires with something that performs well in rain snow (forget ice - nothing'll save yer ass!). I was really happy with the Michelin LTX A/T's and the BFG All Terrains.

Use your 4 wheel drive system only when you absolutely have to - i.e. snow, mud, etc... and you won't have any problems.

Just my 2 cents...

What if I running mud tires, driving in 4H at wet pavement? I guess that the poor traction of the mud tire will allow to slip enough in order to not cause damage to driveline components... But, i don´t know if the front weight(engine, aftermarket bumper, skids, etc.) are enough to avoid mud tire slip...

Another scenario. Here, when rain begins, roads become too slipery, a very slipery thing made of dust, grease and other things is formed and roads get very dangerous. After a time of rain, roads become "washed" and the slipery condition is reduced a lot. So, I guess that at the begining of a rainy day 4wd can be used...

take air

No, it's still not wise. The front tires will do a far better job of steering and braking without the additional work of providing power, not to mention the "slip" of the tires to release driveline tension will obviously make them slip on the pavement and just what good are they doing you then?

Brent

Do you just stay up late at night thinking up stupid shit like this ?

Maybe you should call Subaru and explain to them that AWD really doesn't work as well as 2WD.

No offense to you Brent, but holy crap I actually laughed out loud at Ian's response above.

It's a simple fact Ian, the more power you ask a tire to transfer, the less traction is available for cornering. A free-wheeling tire dedicates 100% of its traction to lateral grip. Same for braking, you scrub off your speed before you reach the apex so the tires have maximum grip during the maximum cornering load.
AWD can help you power through a corner without braking the rear end loose and losing control and help somewhat to negate understeer, but at-the-limit handling is optimized with no power or braking applied. You know that. From a vehicle dynamics standpoint, yes, having the front tires help to pull the front end in the direction you intend is helpful, but in a part-time system you don't want those front tires breaking traction to release driveline tension. That's why AWD works and part-time shouldn't be used in rain.

Brent

Only one tire has to break traction to release driveline load. What if it's a rear tire ? Then the fronts are helping.

I agree that part time systems should never be used on wet pavement, but I still disagree with your initial statement.

OK, so if a rear tire slips for a moment and causes the rear end to step out, who cares if the fronts are helping. It goes both ways. We agree part-time isn't wise on wet pavement regardless...

Brent