What's the difference between 4 Hi and 4 Lo?
 

Just bought a 2006 Toyota Tundra 4X4 Access cab. Really nice truck. What, mechanically is the difference between 4 Hi and 4 Lo? The truck also came with towing package, off-road package and limited slip differential.

about 47 mph:D Deep Reduction, more power to the wheels.

yeah..4 low is when you need extra torque and low speeds..its off road only...

4 hi 4 lo
 

I think the difference is either two clicks to the left or right...depending where in this world you are...:o

Four low is also a good way to teach new drivers how to shift standard transmissions. All the action without the speed.;)

I used to have a '78 Ford 3/4 ton with 4WD and a granny low. I could put the transfer case in 4 low, start out in 1st (granny) and literally walk beside the truck. At idle, it wouldn't move faster than a walking pace and this was useful for finding certain noises when working by yourself. Top speed in low, or at least as fast as I cared to push it, was about 30-35 MPH.

No offense, but if you just spent $30K on a truck, you better read the manual, because 4wd work is expensive!! I rarely use 4wdlo unless I am crawling a boat out of a bad situation or pulling another truck out. I don't live where there are a lot of rocks to crawl over, and it is no good in soupy mud. Not very good in the snow either, fwiw.

In other words, 4 low comes into play when ascending/descending steep inclines or crawling over big rocks and deep ruts. Additionally, I had never been stuck bad enough to need a wrecker UNTIL I got a 4WD. Then I needed one twice in a week. Took awhile to learn, but you can't go everywhere/anywhere just because you have 4WD. After a few years experience I have found I can baby a 2wd vehicle just about anywhere I could take a 4WD.

My 4WDs (one FJ40 in particular) always got me stuck 2x further from help than a 2WD vehicle.

Sidebar 4WD story:
Before my Mercedes-Benz days, I owned a 4dr, 92 S-10 Blazer that I'd ressurected from the dead (totalled at 32,000 miles and given to me, I straightened the frame, hung new sheet metal and drove to almost 200,000 before selling it for a 300TD). It had a 4.3 Vortec and was 4WD too. Compared to most SUVs, I actually used my 4WD quite often in launching a big Jon boat that I owned. I didn't hesitate to back down the steepest, moss-covered ramp to stick that boat in the river. As long as I could keep the front wheels on dry ground I could (and did) launch 'Barco de Juan' anywhere.

The 4wd on recent model MB vehicles is not quite half the reason to have it. The major gains are due to the so-called “ets” and “esp” features. Ets provides braking to any wheel or wheels that are slipping and esp is yaw control, employed to stop the vehicle from slipping sideways. On icy or slushy roads, or when starting on an icy hill, or when hydroplaning, these enhancements to 4wd make dramatic, even amazing improvements in control of the vehicle. In addition, the yaw control makes unexpected critical under-steer or over-steer almost never occur, and goes a long way to correcting itself when it does. While you can go many places in 2wd that you can in 4wd, when snow or ice is involved there is no comparison.

In answer to the original q, the mechanical difference between 4 hi and 4 low is usually an additional gear in the transmission or differentials.

ahhh - now we're getting somewhere. Thanks for all the info, I'm beginning to understand. I didn't know 4 Lo is a separate gear.
More questions:

I am assuming that the torque split ratio is fixed once 4 wheel drive in engaged regardless of Hi or Lo position.

Also, the limited slip differential in the back would give either rear tire traction by putting torque to the tire with traction?

Is the front usually a dedicated drive wheel?

Sorry for the elementary questions but it is my first truck never mind 4 X 4. I should probably join the Yotatech forum!

I’m not going to tell you not to rig your Tacoma to run with the diffs locked in 4-H. But, I will say this: Be very careful where, when and how fast you go with all four corners locked up. As I’m sure you can imagine, you’d better be on some pretty slick stuff when doing it over about 15mph. I’m not sure how the transfer case and transmission are set up for it on the Tacoma, but it seems to me that safety switch may be there for a good reason. I have a Pinzgauer 710K that when all four corners (both diffs) are locked and I’m in high range, on anything other than mud or very loose gravel over 10mph, it sounds like things are wanting to explode from down under. :eek:
Not to mention you might find it hard to make any quick direction changes all locked up like that at higher speeds. The Pinz can also lock it’s transfer case. I’m not sure about the Tacoma. If not, that may actually be a good thing for you and the transmission. I'm sure you know your OR driving. I'd just hate to hear you blew some gears up. :(
I'm into the slow controled crawl mself.
Sounds to me like you’re out to make one heck of a mud slinger. Enjoy. And let us know how the safety switch mods work out.

Also - Knowing you can’t “shift on the fly” in and out of 4-L: That safety switch might have something to do with not letting you jump in and out of 4WD with the diffs locked. That might hurt on the wrong surface.

1. not necessarily, depending on yout T case. my t-case is locked so i think the power is split close to evenly. if it's open then it's just like open diff.

2. that's how it works but i find that when i depress the brake lightly when "stuck" will engage the lsd.. otherwise the high torque makes the wheel with no traction spin like crazy.

3. not on my pathy. you can make it that way if you have manual locking hubs by just locking one of them. i have an open diff up front so it's mostly tire placement that get's me through and the rear push. would love to get that thing locked though or at least stick an lsd there.

as to your original Q:

4hi for wet, snowy, loose surface driving. if you cen go 40mph then you don't need to be in 4 at all
4lo - bad snow, mud, rocks, very steep inclines. stuck. if you can go 20mph, you don't need to be in 4lo.

lowering tire pressure (10-20psi) in off road circumstances does wonders.

I only use 4 low when I am pulling a heavy trailer through sloppy mud or need to blast through a rut. Chevy has an Auto 4wd function that works when in the event I find some soft ground concealed by grass, sometimes you just have immediately gun it and hope for the best, stooping or hesitating to pust the 4wd button can easily be the end of the road until you get pulled out. I have found the using my truck does not get as muddy when I use 4wd.

Yes I always have a heavy jerk strap handy :wacko:

I thought that too until I began hunting flooded rice fields;) ;)

fwiw, when I lived where there was a lot of snow, I found front wheel drive standard transmission better than 4wd.