Rain and "full-time AWD"

I just bought 4 new tires for winter. (3PMSF) If you do this you will be fine driving in all conditions 99% of the time. The debate between AWD/4WD is crazy! I admit I did read every post...and now my head hurts!

 

Unfortunately Limited/Sports model has very little tire options.
I like the 20s Shiny wheels... not getting 17s

 

How would you categorize GM's "Auto 4WD" they've had in their pickups and SUVs (Tahoe, Blazer, Suburban, etc ) since like the 1990s?

 

Not to mention that technically 4wd without lockers or limited slip devices are actually 2wd in some low traction circumstances Adding traction control or brake locking devices would make them AWD/4WD

IMHO, the marketing departments of auto makers screwed the terminology into pretzel.

 

Taking that logic to the extreme, 2WD with open diffs becomes 1WD the second a tire hits ice

Agreed completely on marketing departments...

 

This right here.

 

I am inventing a new term. MWD - Most wheel drive.

There, that should cover it. If you're not locked front and back your vehicle is MWD.

Uh oh, what about selectable lockers? Is it only MWD when unlocked, but when it's not...it's .... Oh crap it's a black hole of AWD/4WD................

Maybe SWD (some wheel drive)?

Here's a NWD (no wheel drive)

 

My understanding of this system is that it is actually just a regular part time system with automatic engagement.

This detects rear wheel slip, and will engage the front axle for extra traction, disengaging it when it determines its no longer needed.

Really no reason an SR5 at least couldn't easily have this feature.

There's no center differential and this typically would not engage on dry pavement.

 

I'd be super excited for a SFA 4R. I had a 97 Grand Cherokee, it rode and handled nice . I remember being in a friend's similar year Explorer that was IFS and thinking my ZJ rode nicer.

For higher speed dirt road stuff, yeah it wouldn't keep up with an IFS vehicle. I appreciated the extra clearance and articulation though. All depends what you're doing with it.

Here it is with 1.75" coil spacers and 30" tires. All stock otherwise, even the shocks.

 

Howdy all, first post here. I am an owner of a brand-new 2023 ORP. Anyhow, one misconception I think some have been making is this notion of torque split. Now I may be the one who's wrong, but my understanding is that a part-time 4WD system that is engaged or a full-time system with a locked center differential cannot have a 50-50 torque split front to back, but rather have 100% torque going to both axles, the reason being because they are now locked together.

For example, take individual axles. There are limited slip differentials where if one wheel is slipping and receiving the majority of the torque, the limited slip will transfer some of that torque to the opposite wheel. This may or may not be enough to get the vehicle moving again, as not enough torque may be going to the wheel with traction. On the other hand though, with a locking differential that locks both wheels together, there becomes no such thing as the slipping wheel versus the non-slipping wheel. They both become just one entity as both get 100% of the torque. Basically it is just the axle itself turning as a singular whole. So there is no torque split between the wheels at this point. Picture a steamroller with one side of the roller with no traction and the other side with traction. There is no torque split between the left and right sides of the roller.

Similarly, with both axles, if both axles are locked together via locking a center differential or engaging the transfer case, they now turn as a singular entity. They both are getting 100% of the torque. If only say the front wheels have traction and the rear wheels have no traction, the vehicle will move no differently than if all four wheels have traction.

Whereas with a torque split, if the rear wheels have no traction, the vehicle may or may not move depending on the terrain as the front wheels may not be getting enough torque to move the vehicle.

 

Very nice! I can't believe what they have evolved the Grand Cherokee into today. I mean it's like watching a wolf get bred into one of those hot dog shaped dogs.

Slightly off-topic, but there is actually a competition called King of the Hammers where solid axle and independent suspension 4x4s compete with one another in both high-speed dirt driving and rock crawling. The rock crawling poses a challenge for the independent suspension trucks and the dirt racing a challenge for the solid axle trucks.

Also, regarding solid front axles for the 4Runner, aren't there conversion kits available for that?

 

This is my thinking too. Congrats on your new 4 Runner and welcome!

 

Think of it this way, if you dyno a 4wd vehicle with the center diff locked in such a way that only one axle is under load and the other is free wheeling, you will not see full power. 50/50 split is still 100% to the ground.

 

What does that mean? Free wheeling? That the dyno is providing no resistance to one of the axles?

This goes back to the example I gave before - only one rear wheel has traction and both the center and rear differentials are locked. That one wheel gets all the torque. That’s why there’s a risk of snapping the axle when you use the diff lock.

 

Thanks. I really miss that thing, it would make such a great trail rig today. It was 15 years old when I got rid of it, and that was mainly because of corrosion and not mechanical issues. The 4.0 ran terrific.

I like the new ones as daily drivers, but yeah they're a far cry from the first two generations as far as capability.

This one here is actually full-time 4WD. In high range it had a viscous coupling instead of a center diff, and as the rear wheels would slip it would send more power to the front. It was fun in the winter for drifting, I could get the rear to kick out before the fronts fully engaged haha.

In 4low, the VC was bypassed and the tcase was "locked*, just as a part time 4wd case would be.

I don't think there are any SFA "kits" for 4Runners, I think that's a custom job. All the SFA 4Runners I've seen have been pretty wild builds, running 38" and larger tires.

I think a SFA 4Runner on D44s and 35 or 37s would be a really cool build that would be capable but still able to be a DD.

 

You cant have 200% of toque delivered to the wheels ... the 4Runner is not a perpetual motion machine.

 

Only "Full-time AWD" by Toyota I am familiar with is in my wife's RAV4. Good in wet/snowy weather here in the PNW AROUND TOWN! We use my P/T 4WD 4Runner on the highways and in the mountains. Just took a trip down south and had 2 full days of ice and snow, followed by one day of rain in and along the Cascades and Sierras. I would not have felt as safe in the RAV and we saw lots of "AWD" cars having problems but that might have been "operator error", though!

 

100% to the ground split 50/50 would be with an open differential. With the differential locked, it becomes like the two sides of the steamroller, i.e. one entity. The front axle will get the same torque as the rear axle.

Now maybe what happens is that with all four wheels locked together, the total torque to the "system," if you will, is reduced, and thus the two axles get 100% of a fraction of the torque? Because I am sure the more wheels the engine has to turn, the more difficult it becomes. So maybe while mathematically one could say it's a 50-50 split, it's really now both axles get 100% of the engine's torque that has been reduced by 50%?

 

It means one axle on freewheeling rollers and one axle on the dyno. You won’t see full power.

 

Found this about diffs but I'm assuming it applies to a locked center diff as well:

The reason that the split is 50/50 is that the axle gears are identical and are driven by one set of pinion gears.

Reference: https://www.physicsforums.com/threa...-in-a-standard-open-axle-differential.566411/

 

So in doing some more research, I found that the TORQUE actually will vary in the system even if all four wheels are locked together. What basically happens is that in normal conditions with all four wheels locked, the amount of torque delivered by the engine is split four ways equally, with 25% going to each wheel. However, now let's say we put the vehicle on rollers where three wheels can spin and only one wheel has grip. What happens is because the wheels and axles are locked together, 100% of the torque (well more like 99.999999% as the wheels on rollers do have some resistance) will get transferred into that one wheel and so move the vehicle.

Now with an open differential system, I thought the opposite happens, i.e. the majority of the torque goes into the slipping wheel, well apparently that's wrong. What happens instead, if I am understanding right, is that the differential still splits the torque 50-50, BUT, the amount of torque that can be applied to the wheel with traction is the same amount as that going to the slipping wheel, and because the slipping wheel is far easier to turn, it therefore needs far less torque to turn, so the wheel with grip thus gets that same small amount of torque. I THINK.

What causes so much confusion is people do not realize or have trouble grasping that the torque can still get transferred around even if all the wheels are locked together.

Here is a good video that explains what we are confused about:

 

Just want to make sure anyone reading this is warned. There's no such thing as a conversion kit that's 100% complete for a SAS of any vehicle that I've seen thus far.

When we did my buddies 2nd Gen Tacoma, we bought the kit from Barnes 4WD and it was very nice, but you still had to do you own figuring out of exact driveline angles, mounts for links, etc. Lots of math, lots of recalculating.

Then we added hydro steering, and had to re-route a ton of stuff because the reservoir is gravity fed.

To summarize, there are kits, but none are complete. Fab skills required.

Side note, even though their customer service can be kinda bad, check out the Marlin Crawler RCLT or something - it was featured on a Dirt Every Day with a 4th Gen 4Runner Fred named Pond Scum. I have not had a chance to see one of those in person, but I think I'd consider that before going SAS, as he ran it on 40's and it was freaking gnarly.

 

I'll have to check out Fred's videos on the Marlin suspension. I also watch Dirt Lifestyle, he installed that kit on his third gen Tacoma, as well as their three link rear kit. He liked the kit a lot, though he noted it was costly, requires fab work, and while it offers a lot of travel it still doesn't articulate in the way that a solid axle does.

I think the long travel IFS suspensions that the king of hammers builders use are pretty interesting, and function impressively. They're just so far removed from what you get in production vehicles, I don't even see it's worth mentioning when talking about the benefits of IFS versus SFA. Not that you did in your post, I'm just speaking in general terms.

 

Yea that Tacoma on UA (Dirt Lifestyle) is really nice.

Also, agree with the KoH stuff. That's a full race truck, not realistic for our daily drivers.

 

Exactly. And for the price of the kit alone, you could build an entire XJ (or buy a built one). I recently saw one on Marketplace with tons, 38s, hydro steering, winch, cage, etc for 10k.

Also, I love how this thread was brought back from the dead and veers on and off topic, haha.

 

With my budget, it's not about being easy, it's about being cost effective, haha.

 

If purchasing a solid axle conversion kit that requires some advanced skills, I'd try to have a decent 4x4 shop put it on and do all that work for me.

 

I'll ballpark you that most shops will come back around $20k - $25k for a turnkey SAS, parts and labor.

Realistically, because everyone wants to say they did a great job for $2000 for a SAS, ours looked like this.
Dana 60, King Dual Rate coilovers, 4 link front. Rear Corp 14 bolt - both with 5.38 gears. Chevy 63 rear, Bilstein shocks. Front 14" of travel.

Parts probably $12,000
6 months of work because all engineering and stuff was done by the guy who owned it.
4.62 miles of MIG wire (joking, but it was at least 4 or so 10lb rolls...)
3 pairs of jeans with welding holes custom installed

He realizes that he could never sell it for what he spent on it. But buying someone else's SAS is kinda sketchy cause who knows what they did. It's all custom on this point.

 

For $25K, something like this would be a better option, IMO.



Or, if someone is just looking for a trail toy, a 2 door Wrangler is probably the most cost effective solution.

 

THat's basically my point. It's not cost effective to SAS.