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Old 01-20-2021, 11:28 AM #1
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4wd no center diff lock

So as I understand it, the center diff lock makes it so there is even power between the front and rear wheels making the vehicle a true 4x4 and helps with traction on slippery surfaces.

Now the trd pro and fj cruiser etc have a rear locker but no center diff lock. Do they then not have this ability to evenly split power between front a rear which is helpful on slick surfaces like snow, ice, rain or mud?

I understand the rear diff has advantages for traction - more off roading or when one wheel is off the ground, but it seems like there are still times where youíd want more front traction for stability

So 4r is a rwd in 2wd and in 4wd the front kicks in so maybe itís like 75 back power and 25 front power. The center diff will make it 50/50. If you have only a rear diff you make 50:50 right and left rear but it doesnít affect the power going to the front - thanks for the help
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Old 01-20-2021, 06:07 PM #2
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On those transfer cases without a center differential, 100% of power is transmitted from the transfer case rear output via driveshaft to the rear axle while in 2WD. 0 power is directed to the front output.

When one pulls the lever to engage 4WD, whether 4 Hi or Lo, 100% of power is transmitted via both transfer case outputs - to the front diff and to the rear diff. This is done by engaging a gearset in the transfer case to power the front output (and remember the rear output is engaged 100% of the time). There is no "split," it's not some percentage - the outputs are locked together, like when an air/e-locker in a diff is activated. Via the gears (and chains) in the t-case, power is applied equally and wholly to front and rear.

The center diff does allow some percentage of power to be applied to both outputs, and depending on model/mfgr this percentage can be static or transition as needed - e.g. when slippage is detected. When you engage the center diff lock, you eliminate this feature as 100% of power is supplied to both outputs ("diff" outputs are locked together).

----

Having owned numerous vehicles with center diff - the V8 4R, GX, FZJ80, old Discovery, Subarus - each mfgr biases them differently. Some may bias power toward the front until slippage is detected, then they can transition power rearward, for example. Some may be static, where they send say 60% to the front and 40% to the rear in normal conditions (my Disco was alleged to be 40F/60R on normal surfaces). We even had a Honda CRV that biased 100% to the front in normal driving, and sent some power to the rear while in snow and sand when slippage was evident.

Whether you like 2WD/RWD vs full-time AWD is purely personal preference. I love the feature, and am completely happy with the tradeoff of lower mpg and more maintenance for AWD and the ability to lock the center when needed.
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Old 01-21-2021, 01:00 AM #3
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The models you mentioned don't have a locking center diff, because there is no center diff to even lock. These are "part time" 4WD and should only have 4WD engaged when you are off road (or in a low grip environment) since it relies on a certain amount of tire slippage to allow for the amount of give needed by the driveline.

A "full time" 4WD has a center diff that allows power to be biased front and rear as needed. Those are the models you see with the center diff locking feature.

The models you are talking about default to 50/50 power distribution, but the "full time" systems (the ones with a center diff) will bias slightly as needed, typically when going around tight corners where different distances are traveled by the front and rear tires.

These aren't like the AWD systems that may bias power all the time to either the front or rear.
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Old 01-27-2021, 03:34 PM #4
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This video, while lengthy, describes (and shows) in great detail how both the traditional transfer case and one with a center diff works. Bonus because the one with a center diff is from a 4R!

Center Differential Transfer Cases - YouTube
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