Advantages (and Disadvantages) of a Centre Differential

[carbon60]

(As always, if I missed an existing thread, please point me in its direction.)

As part of my slow decision making progress on choosing an SUV (4Runner) or compact pickup (Tacoma), I notice that a not-so-minor difference is the availability of a centre differential on the 4runner in some packages. So, that opens the question: what are the advantages and disadvantages of a centre differential? (Otherwise known as part-time or full-time 4WD.)

I currently drive a 1996 80-series Land Cruiser, which does have "full-time" 4WD.

To get it started…

Advantages:

1. Improved handling on loose or slippery surfaces, at speed; particularly snow and gravel;
2. Improved maneuverability/turning radius at low speed, off road;

Disadvantages:

1. Additional system impacts maintenance and the possibility of failure;
2. Worse fuel economy (assuming the vehicle is unable to be put into 2WD mode);

What else?

Thanks,

A.

 

[98OzarksRunner]

On the later 3rd gen 4Runners (01-02) it is 2wd until you engage 4wd, at which time it is really in AWD. To engage true (or 'traditional') 4wd, lock the center diff. It gives the advantages of AWD, as you noted, without the fuel economy and wear hits of running in AWD all the time. I often engage AWD off road when I'm on dry dirt or gravel to avoid wear, and lock the center diff when I start to get into more difficult terrain. I can also unlock the diff in low range, so I have AWD with more torque and control. IMHO the 4Runner multi-mode setup is the best of all since it gives the most options.

 

[carbon60]

On the later 3rd gen 4Runners (01-02) it is 2wd until you engage 4wd, at which time it is really in AWD. To engage true (or 'traditional') 4wd, lock the center diff. It gives the advantages of AWD, as you noted, without the fuel economy and wear hits of running in AWD all the time. I often engage AWD off road when I'm on dry dirt or gravel to avoid wear, and lock the center diff when I start to get into more difficult terrain. I can also unlock the diff in low range, so I have AWD with more torque and control. IMHO the 4Runner multi-mode setup is the best of all since it gives the most options.

That would be the best of both worlds (other than the extra system negative, I guess.) I don't think anything newer has that feature, though.

A.

 

[Martinjmpr]

That would be the best of both worlds (other than the extra system negative, I guess.) I don't think anything newer has that feature, though.

A.

The Sequoia still has multi mode AFAIK. At least I know the 1st gens all did. I believe the 2nd gen (2008 - up) Sequoia's do but I'm not certain.

It's always struck me as odd that Toyota never seems to advertise this feature. IMO it's one of the best things about the 4th gen 4runner and I don't recall Toyota ever using it as a way to distinguish the 4runner from its competition like the Nissan Xterra and (R51) Pathfinder, both of which are similar to the 4runner in many ways, but neither of which ever offered a multi-mode 4wd system.

 

[carbon60]

But back to the question: how does it impact handling?

 

[Martinjmpr]

With all 4 wheels driving it feels a bit more "sure footed" on slippery roads. Obviously in 2wd it's no different from any other 2wd out there. I generally lock the center diff if I'm on a road where I would use 4wd on a "conventional" 4wd vehicle. The main reason I do this is because locking the center diff disables the skid control, which I don't want to have beeping and otherwise interfering with my driving when I'm on a rough trail.

 

[Martinjmpr]

AFAIK with the 5th gen 4runner the only way to get a center diff is to get a Limited, which may or may not be what you want. All 4x4 4runners other than the limited have a standard t-case with no center diff (IOW exactly like a Tacoma.)

 

[tanglefoot]

As for handling, the center differential improves handling greatly when in 4wd, over the part-time, center-locked system. With the open center differential, each wheel is able to track the surface exactly, without being forced to slip. It makes for smooth and effortless curve-carving.

With a locked center differential, the front and rear axles are forced to turn at the same speed when in 4wd. This is fine when going straight, but it resists motion in turns, forcing tires to slip in order to relieve drivetrain stress. This results in a shuffling feeling and braking effect when going around curves, and it's harder on the tires.

The availability of an open, but lockable center differential really is the best of both worlds, as others have mentioned. It allows the smooth tracking of full-time 4wd as well as the added traction of part-time 4wd when needed.

 

[carbon60]

The availability of an open, but lockable center differential really is the best of both worlds, as others have mentioned. It allows the smooth tracking of full-time 4wd as well as the added traction of part-time 4wd when needed.

I believe this is not available in a 5th ten 4Runner, can anyone correct that?

And, unlike the axel diffs, there is no way to add a locker to a centre diff, is there? (Excluding discussion of brake-based traction control, please.)

 

[carbon60]

From Wikipedia regarding the 5th generation 4Runner:

The optional 4WD systems were full-time on V8 models while "Multi-Mode" or part-time on V6 models, both systems used a lockable Torsen center differential.

That sentence doesn't make sense to me.

 

[olsen_karl]

From Wikipedia:

The optional 4WD systems were full-time on V8 models while "Multi-Mode" or part-time on V6 models, both systems used a lockable Torsen center differential.

That sentence doesn't make sense to me.

On all 4th gen (2003-2009) 4Runners:

1) 4WD was optional, vs. 2WD. You could purchase a 2WD (rear wheel drive) 4Runner.
2) 4WD with V8 = fulltime 4WD. Transfer case switch on dash allows selection of high or low range.
3) 4WD with V6 = transfer case switch on dash allows operation in 2WD (rear), 4WD high fulltime or 4WD low fulltime.
4) 4WD with V8 or V6 = center differential includes a Torsen limited slip. It is also lockable via pushbutton, which, when locked, results in a 50/50 front/rear split. (i.e. just like traditional 4WD with a "part time" transfer case.)

 

[Martinjmpr]

I believe this is not available in a 5th ten 4Runner, can anyone correct that?

And, unlike the axel diffs, there is no way to add a locker to a centre diff, is there? (Excluding discussion of brake-based traction control, please.)

With enough money I guess you could put a 4th gen T-case into a 5th gen but it would cost you less to just buy a 4th gen in the first place so I don't know why you'd do it.

From Wikipedia regarding the 5th generation 4Runner:



That sentence doesn't make sense to me.

That's because you're reading the section on the 4th gen 4runner, not the 5th.

 

[carbon60]

That's because you're reading the section on the 4th gen 4runner, not the 5th.

I meant 4th gen! Sorry. Still, I don't understand how a drivetrain would be "part-time" 4WD and yet have a locking centre differential. That's the part that gets me from the article.

 

[Martinjmpr]

I meant 4th gen! Sorry. Still, I don't understand how a drivetrain would be "part-time" 4WD and yet have a locking centre differential. That's the part that gets me from the article.

"Part time 4wd" means that you can run in 4wd or 2wd.

Most vehicles with "part time 4wd" do not have a center diff.

OTOH, ALL vehicles with full time 4wd have a center diff (they have to - that's what allows them to have full time 4wd.)

Essentially, "multi-mode" means "a full time 4wd drivetrain, but with the ability to go to 2wd as well."

Does that explain it better?

 

[carbon60]

Essentially, "multi-mode" means "a full time 4wd drivetrain, but with the ability to go to 2wd as well.

So the V6 has a way to disconnect the front drive shaft while also offering a diff. Nice. I think that is what I want.

A.