Search is down so I am not sure if there is any write-ups on this.

I know it says you can't drive on Hard Dry surfaces in 4Hi in the manual, and someone even told me that I can't use my 4Hi on the Highway even with some snow on it...... Is this true?

What kinda of damage would occur if you drove on Hard Dry surfaces anyway?

 

You can drive in 4 High on or offroad. If you do use it on pavment can can wreck your gears and stuff. But in snow and etc 4 high you can turn it on / off at low speeds as long as your hubs are locked.

 

thats for 2000 and earlier only, correct?

 

For highway you shouldn't need 4hi. At those speeds you don't need 4wd, in fact alot of people don't use it past 25-30mph. Transmission damage will incur if you drive past 50mph in 4hi. I use 4hi only up to 35mph, and thats only on unplowed roads because I have a pickup and usually don't have weight in the back, but 4runners have better weight over the rear axles.

As far as hard packed concrete, your front wheels need to have some slippage or else it is a large strain on your drivetrain components (drive shaft and CV's I believe).

EDIT: And you don't have to worry about your hubs being locked, unless you've switched your 96 to manual hubs, but these came standard on earlier models

 

Not true. Watch your speeds though. Keep it under the max 4WD HI speed (see manual).

The damage occurs from turning. You can wreck the gears in the front diff, etc.

 

My book says dont go over 55 in 4 High... I use it on the highway in the snow.. Me truck drives like its on rails hehe

 

You guys get snow in Cali?

 

i surer hope im right... cause ive driven several times at 65+ in 4hi.

 

I swear my manual said nothing about limiting speed, only that you must be going under 50 to engage it. It said you can disengage at any speed.

At least that's the way I read it, I may have to check again.

 

I thought the same thing....... I believe it says this on that little card on the visor.

I didn't read anything about max speeds though.

 

It does...check again. I think it is also written on the card in the driverside sunvisor.

 

Honestly...its night and day with 4wd on the highway, even better under braking conditions. Especially when I pass all the 2wd vehicles !!!! This is all when there is snow on the highway of course.

 

In my Tacoma , I used to drive accross the salt flats in 4 high around 125MPH or so.. and never had any problems.. I think you just have to be in low speeds to put it in 4 wheel high..

 

You sure? I thought this is only the case in locked differentials. Stock fronts are open. Turning shouldn't be the issue but binding of the front axle in relation to the rear would be an issue. Since a hand transfer case(actual 4wd not AWD) would be the same as having the center locked. Correct me if I'm wrong.

 

so no one knows if this is still true for 2001+?

i was under the impression theyd changed the system in 2001 making it able to be on at any time at any speed, able to turn, etc.

 

With the multimode AWD version can you drive any prudent speed;I squeezed just a hair over 150mph in my AWD Eclipse.

 

It sure seems that there are a variety of different answers or opinions. This makes me nervous as I have been driving in 4hi on and off for the past 2 days. I checked the card on the visor, it doesn't say anything about max speeds etc.. It only states the speed at which you should engage or disengage.



I will check the manual tonight...anyone have theirs handy right now?



:pat:

 

I think the added pressure when the transfer case is engaged causes the damage I am talking about. Ever tried to turn in 4HI and felt that binding and heard the tire skidding?

I am not exactly sure what that is doing, but I have heard it puts excess pressure on the diffs.

 

Does this mean its not good to give it a shot of gas when your in 4Hi??

 

A locker is irrelavent. Part time 4WD biases 50% of torque to the front and 50% to the rear driveshafts. The problem is that without a center diff or a VSC the wheel travel front and rear must be the same to not cause stress on the parts. You are only in danger from the third members back. When you turn, EVERY wheel takes its own path. Try it in fresh snow and look. Because of this in 4WD the two driveshafts cannot rotate the same ammount without tire slippage. The slippage is what keeps the shafts from twisting off or other damage occuring. In mud and snow the tires slip easily. On highly tractive surfaces they cannot. The damage will not be sudden, if you were to try to cause damage it would take a while but it can and will happen.

 

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