4x4 Full Time or Part Time?

Looking for my 1st 4Runner. Setting aside of the differences in the trim levels, wondering how the Torque Split (front/rear) differ?

TIA

 

Full-time is by default 30 front, 70 rear with a center torsen LSD. If one axle completely loses grip, you’ll be stuck which is why you’ll use the center locker for an enforced 50/50.

Part-time is RWD until shifted into 4WD (which is skipping straight to locked) but only for surfaces that allow for slip like dirt or snow so you won’t be using it in rain or dry pavement.

Part-time systems have an axle disconnect in the front axle, the full-time systems always have the front axle engaged so that’s technically one less failure point.

 

Full time is only available with the limited.

 

It is perhaps a cruel twist of fate that the Limited trim is the only one blessed with the superior full-time 4WD system, but cursed with a face only a mother could love.

There’s a guy on this board who bought a Limited and then went to the trouble and expense of having the bodywork swapped out to look like a TRD Pro. If I had it to do over again I would do that.

 

Don't think this is totally true - at least for 5th Gen FT 4WD Limiteds. For most driving situations (good traction/no wheel slipping) the Limited's center diff has a torque split of 40% front / 60% rear. If the front wheels slip it can go to 30% front / 70% rear - so 30% torque split to the front tires is the minimum. If the rear wheels slip it can go to 53% front / 47% rear - so 47% torque split to the rear tires is the minimum. If front wheels are completely slipping - you have at least 70% torque to the rear wheels. If the rear wheels are completely slipping - you have at least 53% torque to the front wheels. Of course this is all with the center diff unlocked. Lock it into H4L (High 4 Locked) and you've got 50% to the front and 50% to the rear. The front and rear differentials are open - so if you have 100% slippage on at least one front wheel and 100% slippage on and least one rear wheel - you are going nowhere. You can go into L4L (Low 4 Locked) and activate ATRAC. ATRAC will use the brakes to stop the slipping wheels - so if you have at least one wheel with some traction you might be able to crawl out. If you are stuck so bad that you have virtually no traction on any wheel - then you need a tow/recovery.

 

Yep. I'm actually OK with the Limited's face - at least OK enough that I bought the Limited because the FT 4WD system was the best for how I would use the vehicle. But if there was an option to get the TRD Pro with a FT 4WD system I would have bought that also.

 

Hi Shooter. I understand how there can be an asymmetrical torque split between the front and rear axles - planetary gears and such. But I don’t understand how the torque split can change. Could you please explain what’s going on in the transfer case, mechanically, that allows that to happen?

 

So this begs the question, how compatible are the transfer cases? Can they be swapped out? Is that a thing?

 

It's more than likely a different 4wd computer as well. I don't think anyone has really done it. A manual shift option would be nice but I have only seen that in Jeeps and Mitsubishi.

2nd gen Montero:

 

I don’t think I’ve heard of a swap being done, I’d certainly be interested but that’ll be a pricey risk for those looking into it.

I can’t fit if the 4Runner has a sunroof so that means no full-time 4WD for me.

You’d have to swap the front axle(?), transfer case and I don’t think it’s clear how the computer and gauge cluster will handle the swap - it could be plug and play since the dial has three positions either way or if those computer bits need to be swapped too.

In my case it’ll probably be simpler to remove the sunroof, weld and paint metal in and swap out the overhead console and headliner.

 

Captain Spalding,

Although I am a mechanical engineer, I am by no means an expert on Torsen center differentials - or even machine design in general. I've spent the vast majority of my 36 year career (close to retirement, woohoo!) dealing mostly with thermal issues/problems (heat transfer, thermodynamics, fluid dynamics, etc...).

The planetary gears you mention within the transfer case drive a sun gear in the middle (power to the front output shaft) and an outer ring gear (power to the rear output shaft). The planetary gears are helical gears that have angled teeth that mesh together with the teeth in the sun gear and ring gear. The planetary gears are mounted on a gear carrier - engine output goes to the planetary gear carrier. When one output shaft, and its corresponding sun gear or ring gear, spins faster than the other the helical planetary gears create a thrusting action that forces them against friction plates. The friction resists the faster spinning gear/output shaft and allows the differential to bias torque to the slower, higher traction output shaft. Torsen differentials do not require electronics or a computer to control function. Torque distribution is determined by mechanical interaction of the planetary gears and friction plates. It's all about the friction. Search how Torsen center diffs work - there are some pretty good videos/animations that do a much better job of describing it than how I (probably somewhat incorrectly) explained above.

 

And I guess that’s one reason to consider the LC250 for full time 4WD.

 

At the time (2023) when I bought my Limited - the current LC250 was brand new with the turbo 4 cyl/electric hybrid and 8spd AT. If I was looking to buy a FT 4WD SUV now I would likely consider it. However, in early 2023 there was still speculation that the 6th gen 4Runner would come out in 2024 - and I wanted the 5th gen 4Runner with the 4.0L V6, A750F 5spd AT, and FT 4WD - admittedly a rather old engine/tranny combo with relatively shitty gas mileage, but rock solid durability/reliability. Who buys a FT 4WD SUV for gas mileage or acceleration anyway? So, I pulled the trigger on a 2023 Limited. I'm an old dude - so I don't mind all the chrome on the Limited - I'm fine with how it looks. It's got ~35K miles on it. I plan to retire in 2026 and the 4Runner will only have ~40-45K miles on it. Once I retire I'll be putting 3-4K less miles on it per year. I figure it will take me about 10 years in retirement to get it to 150K miles. By that time I will have been driving it for 13 years - and will probably be able to drive it for at least another 4-5 years if I want to. If not, I'll just get something new. I drove a 2010 Tacoma TRD Sport for 13 years before I got the 4Runner - and it had 145K miles on it and was running/driving as good as ever when I gave it to my son. The way I take care of it I'm pretty sure I can get this 4Runner to 200-250K miles. I might just see how long I can drive this thing - maybe get a 66/67 GTO for fun after I retire

 

I’m not sure what I think about the new drivetrain on the LC250, but I think it looks miles better than the 6G 4Runner.

 

It wasn't a random choice. All ghey side shirts, airdams, lowered ride height, and street tires are needed to compensate for the full-time system's increased fuel consumption, so the Limited doesn't drag down corporate average fuel economy numbers. Under previous regimes, automakers lived and died for 1 mpg.

The guy I bought my OEM front skid did a Limited build as well - he bought it at the height of covid shortages, where Limited models were easier to get than ORs. Likewise he removed side skirts and replaced bumper covers... then promptly cut up the new bumper cover to mount a winch cradle, etc.

 

I better my Limited has 70/30 front and rear in H4H, 50/50 in H4L, and neck snapping 50/50 in L4L low range. I didn't realize my Limited was AWD when I bought it, but I absolutely love it. You use it in all weather conditions and it's so safe with Trac and skid control. I wouldn't have anything else. It will go everywhere and you absolutely can not sling it out of a curve. It will hold any line I take in a curve and anything else. Even with slick tires it's amazing. I don't know if anyone has really pushed the limits of their's, but I am shocked and impressed compared to older 4runners. In snow and ice it's good to push Trac button 4 seconds and turn everything off so it acts like a normal 4wd or the skid control makes it a bit squirrely trying to find straight ahead. I wanted a ORP or Pro, but I have always had trouble free Limited models. Doesn't hurt my gas mileage at all. With 20s I got 19-24 mpg. Just be honest about the type of driving you are really going to do, versus reality. They are all the same 4runner with different suspension, drivetrain options. With Atrac, you don't need lockers or much anything else. The Pro, ORP use Atrac with terrain selection basically. I'm sure that's nice and everyone wants everything, but I have offroad experience and I don't need all that. Even trail riding, I still drive hwy 98% of the time. A Limited is the last step before a Lexus. Just point and go.

 

Or any 4th gen

 

I worked at Toyota when the 4th came out, but I was driving a 3rd and don't know much about the 4th. A lot of 4th and 5th generation parts are the same thing with a different priced parts number. Toyota usually sticks with what works. I have been looking for extended rear axle stops and I think a 4th gen will fit just looking at them. I was told the 4th used air instead of fluid on the Xreas. I don't know.

 

Of course but we are in the 5th gen section so I didn't see a need to mention the 4th gen. 3rd gen also had it as an option.

 

I'm so sorry. It was in reference to a 4th gen comparison.

 

I also was not paying attention to the forum section.

And I guess any remaining 4th gens are getting pretty old these days, 16 years at least, so not a desirable option for most people.

 

Yeah I never cared for them compared to my 3rd. The interior quality and just look in general didn't interest me in wanting one. They are probably a good value for an abusive offroad 4runner. They just have a lot of stuff hanging off the front and rear body. I've seen a few 2026s lately. I'm not paying that for anything to drive. I'm impressed with 5th gen coming from the older ones.