I experienced something strange with the 4x4 system this morning...

2018 Tacoma 4x4 SR 2.7
So, leaving house early this morning, I turn the knob to 4x4 HI, due to inclement road conditions, and start getting on my way.
(NOTE: This is second time when I use the system since Sep, when I got my truck, and I don’t remember anything weird happening the first time I used the 4x4)
Firstly: I noticed a not so easy acceleration from a standstill, like I had the parking brake still on. (As a matter of fact, I checked on that, just to make sure the parking brake isn’t on!)
Then, after having the truck parked for about 1hr at the hospital, before I start backing up from the parking spot, I turn the know to 4x2, and then proceeded to back up. The dashboard warning light was still flashing when I started backing up, but it was already into 4x2, according to the control knob.
After putting the shifter in D, again, it was hard to accelerate from a standstill. So, after driving about 20ft, I’ve heard a powerful “clank” noise and finally, the system switched into 4x2.
Is this normal for Tacomas 4x4??
My experience was only with Land Rovers systems, the “full-time 4x4” kinda, or AWDs, as in wife’s RAV4.
Am I doing smth wrong here
I read the owner’s manual, but don’t remember of any special precautions for switching from 4x2 into 4x4 (and viceversa), other than can be done with the truck in motion, but under 60mph? So, what gives? Does my truck doesn’t like me?
Or, Do I need to fork the dough for a TRD Pro?

I will also start a search on forum re this issue.
Thx all

 

switching back and forth takes a little finagling. that's normal.

I don't want to assume anything, so will ask... you do realize your Taco 4x4 system is NOT a full time system, right. should not be used on asphalt. it is not as versatile as the previous "full time 4x4" systems you're use to.

 

Hi, couple of things from my perspective.

1. I just started using my 4x4 last week with bad weather as well. You should only use it on slippery roads, and I always turn it back into 2hi before entering parking lots unless there is a significant amount of snow build up covering the lot. This isnt like a auto/AWD system so you should really avoid turning as much as possible when in 4hi/4lo unless there is enough "slippage"

2. The 4x4 will draw more power from the engine than 2hi since you're now essentially taking 50% of the raw power to the front wheels, it will feel marginally different than in 2hi - not sure if it's enough to mimic a parking break feeling?

3. Blinking light means it is in transition.

4. Clunk noise = bad, but I doubt you broke anything especially if it still works next time

 

I know this is the consensus but mine hasn't yet. Just flip the switch and it engages for me, but I've only used it a handful of time so far

 

You sir are doing it wrong. What you experienced is drive train bind.
Lemme guess: you were trying to turn yes?
Use 4x4 only on loose surfaces like snow, sand, mud, gravel. If you have traction issues on wet roads in 4x2 you need better tires

 

I do realize that now

 

Yes, i did turn, kinda sharp too
Anyways, the “clank” noise wasn’t too scary sounding! Will keep your advice in mind for when using it next time in 4x4

 

FYI full time 4wd or AWD vehicles have an open center differential. Your truck does NOT have that. Twist the knob to 4hi and your transfer case locks the front and rear drive shafts together so they cannot rotate at different speeds which is necessary in a turn because one of the axles - depending on the direction of travel - will have to travel a further distance than the other to complete the turn.

 

For what it's worth, the TRD Pro uses the exact same drive train as the rest of the 6cyl tacomas.

 

Wasn’t aware there’s no open diff present! Thx again

 

I find that the 4WD system on this truck binds more than on my old Ford Ranger while turning. However, this truck also has a significantly tighter turning radius that the Ranger had. I think the OEM tires also have better grip in snow than the tires on my old truck did, so that is probably also adding to the problem.

I do get a slight clunking noise shifting out of 4WD, which I don't remember hearing/feeling when I first got the truck. It still engages and disengages, but rarely engages when sitting still in the cold (just blinks), and has done this since I bought it.

I have read elsewhere that the actuator/locking system for the front wheels is weak on 2nd and 3rd gen Tacomas. I guess I'll see how it holds up.

 

Mine is the same way. Went on a very difficult 20 mile portion of road a few weeks ago. Switched between 4lo and 4hi probably 50 times. 4hi to 2wd probably 25 times. Took 5 hours to do the trail.

Not a single transition between drives had any delay or required any finangling. I am glad mine doesn't have any of these issues.

Come to think, my old 01 Tundra never had an issue either. Need to go count my lucky stars.

 

The clunk was more than likely the transfer case switching from 4hi to 2hi. I use 4wd on a weekly basis and have found that it is best to come to a complete stop before changing from 2hi to 4hi and back to 2hi and wait for the transfer case to change gears, you'll hear it if you're listening. 4lo is a bit trickier as you have to be nearly stopped and in neutral to change from 4hi to 4lo and back, sometimes it takes some rolling fore and aft to get the gears to engage, or disengage but i always wait until they do before continuing on my way. The rolling resistance is normal as now you have 4 wheels trying to pull/push you so if you're trying to turn, you'll feel more resistance, going straight you shouldn't feel too much resistance but it will still be there.

 

Don’t mean to thread jack.. but this always confuses me. So how is this different from people adding lockers up front? What you explained sounds similar to a locker?

 

all of the above and it requires motion to engage and disengage 4wd. if you flip the knob that's not enough. you need some travel to engage and disengage it. kinda sounds like you expected it to be in 4wd from a standstill after flipping the knob... if I'm understanding it. anyway all looks good for you now.

 

In 4x4 your only locking the drive shafts going from the transmission to the front and rear differentials. A locker would be in the differentials. In a normal 4x4 like his SR this means that the front and rear drive shafts still spin at the same rate but that's it. The diff still only allows power to the wheel with the least resistance. A locker in the differentials would force the wheels on the same axel to spin at the same rate. It's a similar principle being used but it all depends on where the locking is taking place. It gets more confusing when you start talking about center diffs and AWD. But they don't work in quite the same way.

 

It seems the colder it is out the longer my 4wd takes to engage and seems to clunk more than warm weather,Its always worked just seemed really delayed on the below zero mornings, once everything warms up it seems a lot faster between 2wd and 4wd.Allso it seems if I switch it on and off under a light load it seems smooth to me. If I'm under a heavier load and switch back to 2wd and 4wd it seems to clunk per say.

 

Yup, that's what I do too, usually under 20mph and no throttle and just let it slip in before giving gas. It has worked great so far and I'm sure lessens the strain on the components as they engage and disengage

 

It is similar! The same principle applies to a locked front or rear axle differential when you attempt to turn because the outside wheels (left wheels in a right hand turn, and vice versa) have to travel a greater distance to complete the turn. So if the differential cannot differentiate wheel speed due to being locked you will experience bind. Same as the entire front of your truck if you're going forward thru a turn it will travel further than the rear. Get it?

Also some transfer cases (just not ours) do have lockable center diffs. The AWD equipped 4Runner for example does. When open it allows the front drive shaft to spin independently of the rear drive shafts speed. You press a button and it will lock them together like a spool. Since our trucks are not AWD but part time 4WD they simply don't have a differential in the transfer case. Less parts that can wear and fail I guess.