Alaskan Winter - 4x4 Speeds

[ThePennySaved]

After years of driving a FWD car I bought my 98 SR5 (V6, manual) this fall. I've never owned a 4x4 vehicle and now that the snow is falling I find myself in need of 4 wheel drive on a more frequent basis.

My understanding is that it is unwise to transfer into 4Hi at speeds above 50 mph but that once you are in (at a lower speed) you can go as fast as conditions warrant. Is this true? If so, why? Increased oil temps? Amplified chance of binding? Poor fuel economy?

I know that 4 wheel drive should only be used in low traction situations so as to eliminate binding in the drivetrain (which happens twice as fast in 4Lo).

Disclaimer: I live in Alaska. We get a lot of snow. I have also lived in the Upper Peninsula of Michigan as well as Summit County Colorado. There's a lot of snow there, too. I don't make a regular habit of driving over 50 mph in less-than-optimal conditions but sometimes it's ok. And yes, I know that 4 wheel drive does not help you stop any faster than a 2 wheel drive vehicle.

I'm looking for the technical reasoning and rationale. Knowledge is power, right?

 

[brian2sun]

The newer ('99 and '00 Limiteds and all '01 and '02s) 3rd gens have a different t-case with an "AWD" mode that can be used on pavement and up to about 70-80 mph. Your t-case (like mine) is a traditional 4WD system and 4x4 should not be used on dry pavement (unless you're going straight) or at high speeds. I'd have to look but I think the card in my sun visor says not to exceed 45 mph. You can shift on the fly in/out of 4hi at any speed between 0-45, but you must be stopped and in "N" to shift in/out of 4lo. Keep it under 15 or so in 4lo.

 

[ThePennySaved]

Yeah, the card says to stay under 50 mph but some other vehicle's forums (via google) mentioned that as long as you engage under that threshold then you were safe to travel as fast as you wanted so long as slippage could still occur.

Comments? Questions? Concerns?

I'd rather not give 'er the ol' college try to see how fast and then wind up breaking something that didn't need to be broken.

 

[theizzardking]

Amplified chance of binding, this.

you got alot of parts spinning as your driving and trying to get a few gears to line up and engage the front drive shaft with increased rmp's on a lot of the components makes for a tough time and greater chance to explode something if it doesn't catch right, as an engineer you always write spec's like that with a certain safety factor. usually whatever the industry standard is, meaning that if you can do something at 1000 rmp's you write a spec saying it can only do 990 or 980 rmps depending on the application or use of what your talking about,you do this because no design is perfect,everything wears and nothing is idiot proof
sure you can shift into 4x4 doing 100 mph's (if they haven't installed some sort of limit switch) but doing so is increasing the change of a grenade, increased wear on parts and not to mention the chance that the extra wheels engaging on the front at that speed might send you out of control...but i don't know about that as i never dive over 50 mph in 4x4, lol


and yes if you keep it straight i see no problem in doing 100mph with 4x4 locked , the whole problem from binding and why corners are a big deal with conventional 4x4 systems is the speed at which the front and rear tires take a turn, it's kind of differential 101 sort of thing.

[ame=http://www.youtube.com/watch?v=kJY9SxDOTog]YouTube - How does the differential work? Aroundth1937[/ame]

 

[88xtraSR5]

Like an "IDIOT".... My 2000 model has seen 50 even 60 mph in snow/ice conditions on the highway a few times as did my older 88 truck at 5 a.m. headed to work. But I wouldn't suggest shifting the t-case at any speed above 20 mph, like said before I could imagine after time or the first time something going wrong??:bash:

 

[49Runner]

I'm in your neck of the woods with a '97 auto w/locker. I run 2wd damn near everywhere unless I get some slip and then I throw it in 4wd to stop the wheel spin.

A few weeks back I ran to the valley in the nasty slush in 4wd the whole way (lot's of bad wrecks in the ditch) and down the Seward Hwy earlier this week when it was kinda nasty.

Other then the occasional icy drive way, the last few days have been 2wd all the way.

See you around town...

 

[TheDurk]

I'm sure there are times you can, and times you shouldn't. 45 and below you are ok all the time unless it is asphalt or asphalt-like in terms of adhesion. Above 45 I think you need to use some discretion. I had my Brazilian Hilux SW4 in the high desert in northern Argentina and the roads were dry dirt and straight as an arrow for miles and miles. 4x4 definitely seemed to handle better and I was running between 110 and 115 kph (68-72 mph). I distinctly remember it getting squirrelly if I pushed it any closer to 120 kph. As a general rule, I don't recommend that kind of speed in 4WD or on soft surfaces.

The ground was soft enough that nothing was going to bind and I was only going straight anyway. Even if I left the road, there was nothing to hit except some really stupid alpaca. Maybe three cars came the other way and there was plenty of time to slow down. The only fear was rolling, and I had a pretty good feel for the road that I wasn't going to spin out all of a sudden and then roll. I had to motor fast across the desert, because I didn't want to go down the mountain in the dark. Heckuva place....really desolate. This is the start of that road--12,000 ft. ASL and those are the foothills of the Andes in the background.

 

[ThePennySaved]

I've been commuting out to Wasilla every morning for the last 9 weeks for work but luckily tomorrow is my last day of that. That daily drive was actually the motivation for this post. We both know how interesting the drive to Girdwood can get (not so much your own actions but those around you) and I'm down there every chance I get throughout the winter.

 

[49Runner]

Once the snow flies... binding be damned, if I'm going to Girdwood and the roads are scarey then 4wd is on (turns and all).

Up here it is speed (on these roads) that we need to worry about, don't worry about binding.

 

[brian2sun]

It's good to avoid it when possible, but I agree - sometimes you gotta do what you gotta do. If you're going around in circles in a parking lot in 4lo, that's one thing. But, I live in a place that has lots of curvy, steep roads everywhere and often they are plowed down to pavement with just ice/snow patches randomly and lots of black ice at night. All I need to do is hit one patch and go flying into a tree or someone's house. Sure the 4x4 binds a little, but that's just how it is. Still a helluva lot better than risking it in 2wd. But even driving on the dry highway in 4hi doesn't bind that bad. Plus, we're talking about Toyotas, they're tough as sh!t.

Haha, over the years I bet more electrical issues occur with the multi-mode 4x4 system of the later 3rd gens than mechanical/binding breakages occur with our standard t-cases even when driven like we are talking about.

 

[creatix]

Good advice given above so I won't repeat but to say ultimately we are still dependent on tires to deliver the "bite" to the road surface. Get the meanest, best snow/ice tire money can buy and when the going is rough go slow.