I guess this begs the question, if you are traveling 70mph, why are you in 4wd?

Anway, isnt your front drivetrain not built strong enough to handle highway speeds like your rear? Although not it's purpose, I would bet it is...?

Therefore I would bet it is not speed that is damaging, it's opposing forces (push/pull/turning) that 4x4 LAMM is mentioning on surfaces such as dry pavement due to traction that would cause extra wear and tear on your drivetrain.

So in essance drivetrain wear is always increased when you incur opposing forces and engage 4wd where 4 wheels fighting each other for traction as opposed to 2, albeit less when it is used in conditions when traction is not guaranteed to all drive wheels constantly...

Someone like Gadget needs to chime in hear and clear some stuff up on this...

 

I don't think the front drivetrain is too weak, Think of all the FWD IFS Toyotas that have a setup like a 4Runners, or weeker. The stress only occurs in turning situations so if you want to go straight in 4WD, more power to ya. BTW, I second the notion, why 4WD at such high speeds?

 

well the reason i drove 70+ was because it was wet out with ice rain coming down and i was on my way to the airport... so i took the highway. turned it on intiially because it was really slick on the smaller roads.. then i just forgot it was on by the time i hit the highway.

i dont think 2001's / 2002's are effected by this.. i think they changed it up or something. im ignorant, but remember hearing this.

 

Your 4WD should start blinking if you are driving at extended “high” speeds right?

 

For the record, I've never seen anywhere where it says you can't drive over 55 in 4wd, only that you shouldn't shift between 2w and 4w at anything over that speeds. I've driven over that speed for extended periods and never had any trouble with various (1, 2, and 3rd gen 4runners) versions

 

I think there is confusion here because there are two (2) 4WD HI positions on the 3rd Gen Gear Shift.

4HI- using the electronic button on the side of the shift lever of my LTD anyway, (NOT LOCKED) will not hurt you no matter what you do. You can drive all the time on pavement or what ever you like. I usually use this setting for rainy, icy or snowy conditions or on fire roads where you do not need to lock the center diff but may want 4wd.

4HIL - is locked center diff. My manual recomends only using this setting when driving on forgiving surfaces. Dirt roads etc. Do not use this on pavement.

 

That isn't so. Why would it occur at speeds over 50mph? I have gone 75mph in 4HI. Nothing blew up. No damage occured.

 

I've never had a problem in 4 HI while going 80 mph.

 

Having driven locked drivetrain (hubs, diffs and trans case) trucks in 4WD on dry pavement, I can tell you, you can't miss it. The binding is not subtle at all, at any speed and it's worse the faster your going. Even on high traction off road surfaces (like dry soft sand) it can be a problem.

On the other hand, i've never had a problem with trucks with limited slip or open front differentials, even on dry pavement.

Of course, I always suggest prudent action and risk management.

Bottom line: In my opinion, don't worry about your little adventure in highway 4wd. Your truck is fine (if it wasn't you'd know it already). Chalk it up as a life lesson learned and don't make it a habit.

 

see, thats the confusion. i have 4wd hi, and 4wd lo. no 4wdhiL.

word.

 

I have a 2000 limited with the 4WD/AWD system but my OM has both types of 4WD systems in it. The funny thing about it is that if you have the regular 4WD system with just 2WD/4WD-hi and 4WD-lo. It mentions nothing about damage on the road if driving on dry pavement but recommends using 4WD-hi on wet, icy or snow covered roads. Nothing about maxium speed but engage under 50 mph. You can take it out of 4WD-hi at any speed. The only time damage is mentioned is when the AWD/4WD system is driven on dry pavement while in 4WD-hi-low which is when the center locker is engaged.

 

I'm going to have to say that you are wrong. I've driven 70 mph without any damage. My manual says I can go 103 mph in 4HI. I only have to be going under 50 when SHIFTING into 4HI. I seriously doubt they would limit the speed for 4HI on models later than mine.

Damage will occur if you drive on high traction surfaces in 4HI only if you are turning. Yes, your front diff is open but that isn't were the damage will happen. Your transfer case (or CVs) is where things will break. Unlike full-time 4WD (AWD), we don't have a center differential to allow for the difference in speed between the front and rear axles. This is what will cause the binding and the damage should you make it bind too much.

Sorry if I repeated anything. I kinda skimmed through the thread.



EDIT: Fixing my mistakes as I learn more.

 

With your open differential 4X4 you can drive in 4H or 4L on high traction surfaces all day long without endangering any vehicle components as long as you drive in a straight or near straight line. A slight turn is considered near straight. When you're in 4H or 4L on high traction surfaces and attempt to turn you'll feel resistance in the steering wheel and it's telling you the front drive shaft is starting to bind, stress is mounting on the CV joints, and you're wearing a little rubber off your tires. In order to make sharp turns in 4H/L you'll feel a lot of resistance and a little Armstrong has to be used to turn the wheel. It's not very common but occasionally, you'll blow a CV if you make enough turns in 4H/L. If you're locked up front with a full locker and drive in 4X4, you'll feel a ton of resistance at the wheel and you'll blow CV's more often turning sharply on high traction surfaces. As far as driving down the road in 4H, you can go 100 mph if you want to with no more adverse effects on your drive train than if you were going 25 mph over the same distance. The transfer case only cares about how fast you're going when you engage 4H as it can only synchronize the gears up to a certain speed, the T-case don't care how fast you go or when you attempt to disengage. In most ISF vehicles you'll hear a beeping sound when you try to engage 4X4 beyond the speed that the T-Case can handle - no harm done trying except the beeping is just telling you that you're an idiot! Most people with IFS drive in 4H down the freeway once every month or two for 10 to 30 miles at 70 mph just to lube everything up. In snow country it's not uncommon for people to drive most of the winter in 4H.

 

After checking my manual again, it was just as I remembered.

For mine, it only mentions to engage under 50, and disengage at any speed. No mention of damage on dry surfaces, but it does mention H2 is for use on dry surfaces to minimize wear and provide the best economy and quietest ride. On the button-on-the-lever type, it actually states 3 times damage may occur in H4L or L4L on hard dry surfaces. Again, no mention of a max speed.

Now ADD models (auto disconecting diff) is mentioned in my visor card to not exceed 50mph. However this is not in the manual anywhere. ADD is mentioned in the manual to follow shifting procedure and engage for 10 miles each month. But no mention of what it actually is or which vehicles have it. There is a diagram of the hub that looks like all 4Runners I have seen.

Not even any mention of if my center diff locks, though I'm sure it does. Toyota could be clearer on this, no wonder there is so much confusion.

 

Keep in mind, rarely are tires EXACTLY the same height, even when bought new, there are variations. The tension will be felt in the transfer case, which is then transmitted to the front and rear driveshaft, which then puts the strain to the tires, which will "scoot/skid" along the pavement when there's a discrepancy, unless something else becomes the weak link. So if you drive way 100 miles, even without turning, you're still stressing the driveline if you're on a hard surface. No, it probably won't break it the first time or the second, but it puts a lot of premature wear on it and everything fails sometime, it's just a matter of how long.

 

If it makes anyone feel better, my max speed in 4 Wheel low is about 15MPH LOL... (with the tak taking out)

 

Not to add to the confusion, but ....

I remember the dealer telling me that I could drive my 2001 SR5 in 4H on dry pavement, because it now had the 4x4 system that used to be available only in the limited, which allows for dry pavement.

He said that this is why I should be a new 2001 vs. a used 99, like I had been thinking of doing. He said driving the 99 SR5 on dry pavement would be bad, really really bad.

Does anyone know of what I am talking about? This is one answer where the limiteds and SR5s will have different answers for different years.

Glenn

 

I have a 99, and I believe it was the first year they offered this option, and it was only on the limiteds (mine's limited). The option is basically an AWD mode. This mode leaves the center differential unlocked, so that the front and rear axles can turn at different rates without binding up. A center differential can take up the slack so there's no binding. If i were to put my 99 in true 4wd, where the center diff is locked, then yes, I would have a problem on dry roads, as it would bind just like any other 4wd. I kinda thought the awd was dumb whne I first got my truck, but after a trip to colorado, I used it the whole time. I'll still use true 4wd for offroading or serious stuff, but for lighter detail, the awd is the $hiznit.

 

this was EXACTLY what i was told about my 2001 sr5 and is what i was trying to say earlier in the thread.

got a little nervous there...

 

I always assumed that was the case, that's why I'm confused, since the OM doesn't tell me to stay off of paved roads in H4 with my "lever type" (Toyota calls yours "lever/button" type in my manual). Seems to me that would be pretty important stuff to leave out.

I'm also trying to figure out what ADD (auto disconect diff) does, if I have it, and why it has a warning about not exceeding 50 MPH in H4 with ADD on the visor card but not in the manual.