Truth behind front to rear power distribution?

[wturner]

I understand that when a vehicle with a locking center diff like my D1 (and H2, according to the website??) sends 50/50 power distribution to the front and rear when locked. I have not gotten out and measured the wheel speed but from my experience in steep loose/slippery grades I think the D1 stands true to its word. Am I right?

I just watched a 30 min special on INHD (cable high def channel) about ?tricked out H2?s? and they showed some off-road action. When this H2 was climbing a grade of loose dirt, I could clearly see that both rear wheels were spinning faster than either of the front. This tells me that either the center diff was not locked, or the folks making H2s are lying about a center locking diff.

What is the deal?

 

[CaptainSpalding]

I understand that when a vehicle with a locking center diff like my D1 (and H2, according to the website??) sends 50/50 power distribution to the front and rear when locked. I have not gotten out and measured the wheel speed but from my experience in steep loose/slippery grades I think the D1 stands true to its word. Am I right?

Re: the Disco - CDL is in there and working. Next time you're on hard packed dirt with tires fully inflated, engage and disengage it. You can feel the tires scrubbing subtly when it's engaged.

Re: the H2, unless you can see all four wheels spinning, you can't be sure of the difflock issue. Front and rear tires on the same side can spin at different speeds even with the CDL locked. Unless you have axle difflocks locked too. The CDL only ensures that the f/r driveshafts spin at the same speed. Not the wheels.

 

[p m]

BJ,

open differential sends equal torque to both axle- or driveshafts, locked - forces them to spin at the same rate regardless of traction (torque) on either shaft.
When the traction is the same (hard pavement, straight line), both locked and open diffs send equal torque and equal power to both axle/driveshafts.

In general, power used up on each wheel is a product of traction and spinning rate.
examples: one wheel on ice spinning, another jammed solid against the rock. The first wheel has little traction (but not zero), and it spins; the second has a lot of traction, but it is stalled. The first wheel receives the power, while the second is not. If you lock the axle diff, if forces both wheels to spin at the same rate; since the second wheel had the most traction, it now receives the most power.
Same argument goes for axle/axle power distribution.

 

[MUSKYMAN]

damn peter...thats the most confussing explenation I have heard you make yet

 

[DeanBrown3D]

Basically a diff lock does one thing only, keeps the axles locked at the same speed. It has nothing whatsoever to do with power or traction (those are difficult to work out).

How a power-split is controlled by some mechanical or electronic means is beyond me, maybe someone can enlighten me?

 

[p m]

okay Thom, will a single statement do?

"Open differential sends equal torque to both axle- or driveshafts, locked - forces them to spin at the same rate regardless of traction (torque) on either shaft."

 

[D Chapman]

okay Thom, will a single statement do?

"Open differential sends equal torque to both axle- or driveshafts, locked - forces them to spin at the same rate regardless of traction (torque) on either shaft."

Not always true...It is in these two said trucks, but something like a GMC Syclone/Typhoon has a 40/60 split. They did this so the truck did not go sideways when you stomp it. I wonder how they did that?

In an H2, don't the ftont end have somthing simular to a TT? That could explain something...If the guy stomped the throttle and got, lets say, the front left spinning, then the "TT" started to pull the right side tire, maybe that got the left front to "take off" and spin faster while at the same time the guy lets off the throttle????

 

[p m]

Dan, it is always true, and it is nearly the only undisputable statement about open and locked diffs. But incomplete - it doesn't say anything about torque-biasing differentials.

It is extremely difficult to get the "truth" out of car salespeople about how exactly is 40/60 split achieved.
Think of an open diff as of an old-time balance-beam scale.
The unequal split is a balance-beam scale with uneven arms. It is as if a Disco would have a t-case output with 1.22:1 high range ratio to the rear, and 1:1 to the front.

 

[D Chapman]

Dan, it is always true, and it is nearly the only undisputable statement about open and locked diffs. But incomplete - it doesn't say anything about torque-biasing differentials.

It is extremely difficult to get the "truth" out of car salespeople about how exactly is 40/60 split achieved.
Think of an open diff as of an old-time balance-beam scale.
The unequal split is a balance-beam scale with uneven arms. It is as if a Disco would have a t-case output with 1.22:1 high range ratio to the rear, and 1:1 to the front.

So would the front and rear end use two different ring and pinions so the tires turn at the same speed?

 

[D Chapman]

Never mind, I got it:

The BORG WARNER-4472 transfer case is a two-piece aluminum case, chain driven, viscous clutch type transfer case. This produces a system in which all wheel drive is engaged all the time. Torque is transmitted through a planetary gear set which distributes torque at a ratio of 1/3 front 2/3 rear. All wheel drive is automatic and has no external controls. The viscous clutch used in the BW-4472 is a torque distribution device and is nonserviceable. The internal construction of the viscous clutch consists of alternating plates that are connected to the front and rear outputs of the transfer case. The viscous clutch is filled with a high viscosity fluid which flows through slots in the plates. The resistance to sheer causes the plates to transmit torque.

 

[p m]

perfect, so that's almost exactly how it is done.

So would the front and rear end use two different ring and pinions so the tires turn at the same speed?

no, but the satellite gears in the center diff will always be spinning.

 

[LuisC]

This may help.........
http://auto.howstuffworks.com/differential.htm
http://auto.howstuffworks.com/four-wheel-drive.htm

Luis

 

[wturner]

My real question was...

When this H2 was climbing a grade of loose dirt, I could clearly see that both rear wheels were spinning faster than either of the front. This tells me that either the center diff was not locked, or the folks making H2s are lying about a center locking diff.

What is the deal?

This was on High Definition TV on my 52" widescreen so I could "clearly" see all four wheels. So either the center diff was not locked, or the folks making H2s are lying about a center locking diff.