Snorkeldepth

Why did 4 wheel / All wheel drive revolutionize rally competition?

Snow: http://www.swrt.com/cpimages/483799.jpg

Dirt: http://www.swrt.com/cpimages/504853.jpg

4Crawler

iTrader: (3)

I think the "official" Toyota party line is under 50 MPH from the Owner's Manual. I've probably gone faster out in the desert, like on a dry lake bed. I've run 70+ with front hubs locked in 2WD.

CoedNaked

My understanding is the front drive shaft is not designed for use over 50 MPH.

Also, changing lanes through slush at 70 MPH? 4wd will have no affect on your control when changing lanes through slush at 70 MPH.

Why the hell would you need to use 4wd over 50 MPH, let alone 30 MPH?

Rediculous.

4Crawler

iTrader: (3)

My front and rear driveshafts are now identical. I actually duplicated the front shaft design for my rear shaft (CV joint on top, u-joint on the bottom) and that shaft in the rear will run as fast as I want. Same with the front, as long as you have the shaft aligned and balanced, it'll run just as fast as the rear. Not familiar with the speed ratings of the IFS CV half-shafts, but there are millions of FWD cars out there running CV half-shafts at speed day in, day out.

Why run 4WD fast? I find on washboard gravel roads, I find I get a smoother ride and better control in 4WD. On long straight stretches of road, you can easily hit 50+ and be in control. Comes in handy for those big basin & range valleys like this one in western Utah:



http://c-67-170-224-64.hsd1.ca.comca...p_2004/41.html

oly884

Slush, maybe not, but ice, you bet. I've been in 2wd changing lanes with ice in the center, but the lanes being dry and i got a touch sideways. 4wd, not a problem with it, and i do a ton of driving in conditions like that.

Oh, and to answer your question, i've got 80 mph in 4wd. Patchy snow, i just don't trust 2wd enough.

Snorkeldepth

The only reference to 50 mph I can find in my owner's manual is:

"To shift from "H2" to "H4", reduce your speed to less than 50 mph (80 km/h) and move the front drive control lever."

It doesn't say to limit the speed of the truck to less than 50 mph while in H4. Interesting. Does this mean to limit the speed to less than 50 or reduce the speed to 50 to shift into H4 and then drive whatever speed you wish. The manual also says to reduce speed to less than 5 mph to shift to L4. Does this mean to limit the speed of the vehicle to less than 5 mph while in L4?

Flamedx4

Yep, me too. Total agreement.
(There are a lot of wide open spaces out there where 60+ in 4wd on ice and snow is not *really* crazy.)

Dexter: Never drive in 4wd at speed on dry pavement though - the front and rear tires are typically not going to be the same loaded radius, and without a center diff you are putting tremendous strain on the tcase. Overheating, bearing failure, great way to throw the chain...

4Crawler

iTrader: (3)

I think that is similar to what I have read. Some of that may have to also do with ADD and making it spin up to speed. I have shifted between H2 and H4 and back (front hubs locked) at higher speeds. And for L4, you pretty much need to be at a stop to shift, unless you double clutch, to make that gear change. I've done about 40 in L4, pretty much limited by your engine RPM.

I've also driven many hundreds of miles in front wheel drive when I have been breaking in new gears or when I have had rear driveshaft problems. I think my '85 drives better on the highway in FWD than it does in RWD.

snap-on

I had rear drive shaft problems for a while didnt have it in so i was driveing around in 4high on just the front wheels (front wheel drive) i could easly do 70-80 down the interstate no problems

I figgured the guys with real 4wd bashing through the desert do the same thing.

In 4 low i max out at about 30-40mph with my 5 speed and only about 25 in my auto.

deathrunner

I have hit 65 on my speedo in 4WD, but my speedo is off by 10% I have been told (33's with 4.88) so that would put me at 71.5 mph. I also notice that the ride is alot smoother with the hubs disengaged. For example between trails, when I am in 2wd, the vehichle vibrates and doesn't want to go past 75 with the hubs locked. With the hubs unlocked I can hit 90 without vibrations.

WVUTaco

I, as well drive in these conditions alot. I always wonder whether or not I may be using 4wd too much or not enough.

AK95Taco

It’s all been pretty hashed out here but I thought I would share my experience too. Living in Alaska road conditions varies widely from dry pavement to glare ice with standing water on top of it (and that can happen in the span of a mile on the dame day). The general practice up here is to just through it in 4wd when the snow flies and take it back out in the spring.

My daily commute entails freeway driving where the majority of traffic (me included) is doing 65-70. The people that drive at a much slower pace are actually in MORE of a chance of causing an accident than just driving with traffic. The condition of having dry pavement in the lanes of traffic and a buildup of snow and ice between them is actually quite common. The advantage to 4wd in this case is that you have at least 1 drive tire on dry pavement as you cross lanes. Where as, with 2wd it is possible to loose traction while crossing lanes.

To date my Taco has 198k miles, half of which have probably been driving in these conditions and I have had zero issues with any of my front drive train equipment. Also realize any ADD equipped Toyota is already spinning one CV shaft, the ring and pinion, and the front drive shaft regardless of 2wd or 4wd operation.

Most importantly though is drive to match the road conditions. If there is a possibility of snow and ice don’t make sudden changes in direction or speed. Also try to limit your actions to either steering or speed changes and not do both at the same time. 4wd is wonderful and makes winter driving much safer, IF you realize its limitations and drive sensible. As has already been said 4wd doesn’t help with slowing down, and really only helps with steering if you are maintaining or increasing your speed (not while decelerating).

Just my $.02

cccp

I have automatic locking hubs on my runner and which is the best way to lock them, i usually stop put the car in park put in 4wd and then put in in drive, is that ok to do? Or can i also stay in drive but be stopped all the way and change from 2wd to 4wd? I dont know if it is safe to lock the hubs while moving so i never done that.

4Crawler

iTrader: (3)

With automatic hubs, you have to be stopped to engage 4WD (shift from 2H to 4H). Should not matter what gear the tranny is in. But you need to be stopped since there is nothing to "spin" the front driveshaft up to speed and since the t-case is not syncromesh, the only time the front and rear shaft speeds are equal is when they are both at 0 RPM (i.e. dead stop). Once locked, you can shift back and forth between 2H and 4H on the fly.

cccp

When i usually drive in 4wd i try no to go past 65mph. And why do i got that fast in 4wd? Well thats cause some parts of the highway is dry but i still think there are some icy sports on the road so i try keep it in 4wd just to be safe.

AxleIke

I'm not saying your wrong, but i think the newer ones do have syncromesh...my dads 97 can be shifted into 4hi from 2hi at hwy speeds, however, there is a bit of resistance on the lever so you pull back with steady pressure, it goes half way then stops, then lets you finish pulling back into 4hi, no grindin, no nothing...

As for the driveshaft not handling 50 mph or above, that would have only been an addition when ADD came into existance on toyota trucks...my friend has an FJ40 that came stock with drive flanges, and the front driveshaft turned all the time, so at 70 mph in 2wd, the front was still turning.

4Crawler

iTrader: (3)

I was talking about "automatic hubs", not "Automatic Differential Disconnect" like the newer vehicles have. And yes, ADD does have some mechanism to spin up the front axles and driveshaft when you shift from 2H to 4H as you are moving. That mechanism is likely one of the factors that caused Toyota to put the "shift into 4H below 50 MPH" note in the Owner's Manual.

chubbydude

I agree with AK95Taco, that driving in 4wd in unpreictable road conditions at high speeds (55-65) is safe and does no harm to your vehicle (not on dry pavement and use equal size/wear tires on all 4 corners). Just think of cruising in 2wd on snowy road conditions, at any speed, and having your rear end start spining and kick out on you in a straight stretch because you start going up a slight grade. 4wd avoids the surprises with your vehicle's handling, while you can concentrate on driving defensively and concentrate on the road far ahead.

I disagree that 4wd does help to stop. Gearing down and using all 4 tires to engine break is useful for all non 4 wheel ABS'ers.

AxleIke

then i would say that i am very confused...if there is no ADD, then the driveshaft is spinning same as the rest of the front end, no? On my friends 94, he has drive flanges, which i always assumed were "automatic hubs", but maybe there is a difference and i have been confused? anyway, his whole front end spins all the time. I am very curious though, and i could be totally wrong, but i'm just trying to figure out what's going on.

as for going and stopping, 4wd will help you go on very icy roads, but you still can't stop your car...for example, if 2wd can't make you go, but 4wd can, and you are on a snowpacked road, and a deer runs out in front of you, no amount of gearing down is going to help you...not only that, but 4wd causes your steering to be a lot worse in the snow than 2wd, which can also have bad results...

4Crawler

iTrader: (3)

There are three types of front hub/axle combintions.

1. Good old manual locking hubs, turn one way to lock, turn the other way to unlock

2. Automatic hubs: http://www.4x4wire.com/toyota/tech/autohub/ that lock and unlock automatically

3. Automatic Differential Disconnect: http://www.4x4wire.com/toyota/tech/add/ which has drive flanges on the wheel hubs and then a gizmo on one side to automatically disconnect and reconnect that half shaft to the differential.