Wait... so how does 4WD work on this truck?

Hey all,

I'm about to ask a really stupid question, and I apologize. Please understand that this is my first truck and my other car is an AWD, so I assumed (maybe badly) that 4WD in the Tacoma works the same.

Long story short, the conditions around my house are piss poor. Ice, snow, etc. So, I've been putting the Tacoma in 4H when leaving the house and driving around town, but not turning it off even if the roads were ok. I thought all was fine until tonight. Pulling into a parking spot in 4H, I felt the tires skipping and struggling, making the car lurch and brake on it's own. I freaked out a bit, thought maybe something is rubbing, but it felt more like the diff(s) are locked to some degree.

So I read the manual and I'm seeing indications that 4WD should be used "in conditions where tires can slip".. so offroad, snow, ice, sure, but not onroad? How is this 4WD system different from my AWD? Do the two diffs not let the wheels spin independently? If so, to what degree are they "locked"? I assume that not all the way as that's why I have the option to lock my rear diff. Or am I speaking crazy?

I ran 4H on the highway when it was slushy out, around town like I said, I didn't realize I may be causing damage. I thought the whole point of 4WD was... that

Please be gentle :-\

 

The center isn't a diff, it's a transfer case. As a result while 4wd is engaged, power is split 50/50 front and rear.

In your AWD car you effectively had three open differentials, and a computer actuating the brakes on each of the four corners to move power where it needed to be. (Slowing the slipping wheel.) In your truck, you have an open front and rear diff, and imagine the Transfer case as a LOCKED center diff.

When you go around a corner, the front travels a longer path than the rear. This causes the skipping and struggling you experienced, since the center doesn't allow for that.

 

This link is pretty good... http://gearpatrol.com/2013/03/29/four-wheel-drive-vs-all-wheel-drive-everything-you-need-to-know/

your car had Full Time All Wheel Drive. Your Truck is a Part Time Four Wheel Drive.

 

The skipping you are experiencing is called driveline bind. Like said above when you turn your wheels move at different speeds. It can't adjust for that while 4wd is on as everything moves at the same speed.

Only use 4wd when conditions are poor and never use it on dry pavement as you can break things. Even in snow and similar conditions, try to avoid sharp turns. If you're attempting to park turn off 4wd and make sure it's disengaged.

 

AWD has a center differential so the front and rear tires can turn at different speeds [as in when turning a corner] while the center differential ''slips'' to keep that grabby feels you had. That grabby feel can break and wear drive train parts because either the tires slip to equalize the forces, or parts break.

Off road though, a 4wd system tends to be more robust and lets power to go to both axles equally which is better for traction on slippery ground.

 

Thanks guys! Holy crap, I can't believe I didn't realize this till just now (a couple of weeks into owning the truck). I just found https://www.tacomaworld.com/threads/rear-wheels-lock-up-when-i-make-sharp-turns-in-h4.119550/ and a few other threads, I'm REALLY glad I didn't use 4H around town much and noticed it quickly tonight, hopefully no damage done. The wording in the user's manual is a bit awkward so I didn't realize what it was implying, though I'm only blaming myself here.

Ok, who has my Dumbass of the Day award? I'll take it. You can even engrave my name on it.

 

Fresh meat!!

jk

I think everyone can always learn more, and questions are a great way to get there!

I'll try to help, but I'm sure other people will help even more

AWD means all 4wheels are always engaged, and some AWD systems vary the load between front/rear depending on slip. 4WD systems you have to engage, and are only intended to be used in 4WD on surfaces that the tires can slip on, and like you mentioned this means wet/snow/dirt/sand/etc. Even then it's best not to make very hard/tight turns because this can put a lot of stress on the gears and stuff inside the system.

You have 4HI that is more intended for slow to higher speed, like it sounds, and it can be engaged while moving up to I think 55mph (check the manual). The 4LO is only intended for crawling speeds, and this is so the truck can generate a lot of torque and climb obstacles at a crawling speed. Going really fast over obstacles has a tendency to break things, slow and steady does the trick. Typically you would only engage 4LO if 4HI isn't allowing you to get over/out of an obstacle, or if you're pulling up on something that you know from experience calls for 4LO. This basically means you wouldn't engage 4WD unless you know you're about to be driving in some bad snow, or a nasty trail, but if you are about to make a sharp turn (say turn into a parking lot), you'd want to disengage the 4WD before making that turn.

4WD really shines getting out of poor traction spots (say stuck in the snow or mud), crawling over obstacles (bunch of rocks or logs), or getting you down a trail/road with really bad conditions. Mostly you can run the truck without it, and then only engage it when you're having some difficulty.

Hope this helps a little

edit: just wanted to say some trucks do now have an auto 4WD system that will engage and transfer power in a similar fashion as AWD when placed in that mode, but still have 4HI and 4LO for full time engagement. The F150 (Lariat and above trims) has this feature, and I'm sure others do too

 

You can use 4wd all day on pavement so long as you're driving straight, though not like you need to (just for explanation sake). It's the turning that's the issue.

 

I wouldn't worry too much about parts breaking at low speeds. But certainly don't make a habit of using 4wd when it's not needed. Primarily in the snow, on ice, in the sand, or other rugged, limited traction areas. Where the limited traction allows the wheels/tires to slip. Toyota has built a pretty rugged truck.

 

You guys are great, thank you very much for all of the explanations, and thank you for not roasting me for my mistake

I'm off to read about TRAC, AUTO LSD, A-TRAC, etc., found a couple threads about that as part of this lesson. I'm done being uneducated (or so I hope).

Happy New Year to all of you

 

How about rain? That is where I never know what to do with 4x4? I get it with snow, ice, mud...but can you engage 4h or 4l driving down the interstate in rain?

Is it safer, or nah

 

You should take the time and read this thread. It's long but great info.

https://www.tacomaworld.com/threads/a-trac-trac-auto-lsd-explained-easy-to-understand-i-hope.70551/

@David K for taking the time to educate all of us.

 

Are you in an auto or a Manual?

 

Thank you... and I have made newer versions for the changes in 2012 (the additional or tenth drive mode).

 

Happy New Year to you, too!
Welcome aboard!

I am more than happy to help... either to clear up something I wrote that may use way too many words to make it simple or to help you enjoy the truck.

I am on Tacoma #3, all 4WD and all the OFF ROAD TRD. I did have a full time 4WD Jeep (AWD is the term always used now) so I am familiar with having a middle differential vs. a transfer case.

Let's face it, if you needed 4WD in dry weather or rain, then ALL cars would have 4WD. So, think that way if you are wondering about using 4WD in town or on the highway. The fuel mileage also drops a lot in 4WD. Use 4WD when your tires spin (loss of traction) for safety and to move ahead.

L4 (LOW RANGE) is for really nasty stuff where having more power and to crawl slowly over or up really rough conditions. The truck will amaze you. If you got the OFF ROAD then it is pretty much unstoppable as it has additional traction in L4 that turns the truck into a tank... called A-TRAC (and in 2016, CRAWL Control).

Enjoy!

 

Mine is the 2016 OR 4WD, so yeah, I have all the bells and whistles, hence the steep learning curve

I think all of this trouble originated from my AWD car, honestly. I'm not sure if any of you have driven an Evo (X or 10), but the car comes with an amazing AWD system. Long story short, with all the electronics on, you are glued to the road in all conditions. If you turn off traction control, the diffs do their work without computer interference and you're riding a bullet train on rails. The car excels at things like auto-cross for those reasons. So, having that in my garage, I thought the 4x4 would basically be the same thing. Well, I was WAY wrong and it's embarrassing that I'm just now realizing that as I think of myself as a "car guy". But after reading about the 4x4 system (and thank you David K for your contribution to all the threads I've been reading through) I'm actually even more excited about it as it sounds perfect for offroading.

I will also add that I was worried about driving a truck in 2WD mode through bad road conditions because in my mind trucks need sand bags in the bed and are death traps in the winter. All that preconceived nonsense is now slowly making its way out of my head

 

Actually I'd be most concerned with breaking parts at low speed. Slower speeds is when you have a tendency to make sharper turns. Couple weeks ago at an Offroad event I attended a jeep broke an axle trying to line up for an RTI ramp in the parking lot because he was in 4wd. And that's just one of many I've seen lol

That's also why in Moab on the slick rock we generally have to unlock a hub to make some of the turns because the rocks act like asphalt.

 

I had a 2009 RAV4 with AWD, and it did handle sharp turns differently then the Taco does. As people say, AWD allows for center slip and differing wheel speeds, 4WD tends not to.
I have noticed also that when I do have to use 4WD, on turns I actually get a bit more tire rub then I do in 2WD. I figure the suspension is loading up just enough to make the tiny difference to account for the extra rubbing.
I use mine VERY sparingly, usually when trying to climb a snow covered gravel road, or slogging across a wet pasture in the muck to get hay. Other then that, almost never.
As Garrison Keillor once said "The primary advantage of 4 Wheel Drive is that it lets you get further back in the woods before you get stuck!"

 

Yes, I understand the confusion. AWD is for ALL roads and 4WD is for OFF roads, lol!
The reason a 4WD system is better off road is that the power is split 50/50 (front/rear) vs. AWD which tends to not be even. The middle differential can remove power from the half that is needed. I think Subaru's AWD system is the only one that does better than most AWDs?

Now, a truck is an issue if the bed is empty or lighter than the front half. It will slide out much easier in 2WD. It would be sweet if we could choose FWD (Front Wheel Drive) for when the bed is empty instead of using 4WD in bad rain on curves or slippery roads. The traction control in 2WD starting in 2009 really improved the truck's handling. TRAC or AUTO LSD (TRAC OFF) in 2WD helps prevent the truck from slipping at take offs in wet weather. Otherwise, put it in 4WD if the rear spins-out (pre-2009 Tacomas did this).

Keep playing with your new Toy and send me a PM or email if you need any questions answered off the forum.

 

Can confirm that an '07 with none of the computer controlled gizmos, and a mechanical LSD in the rear, on mildly wet Texas roads (read oily.) results in going backwards if you're not careful.