What is happening with T-Case in 4Hi and hubs NOT locked?

[wired1000]

The TM says that for 4wd to be engaged, T-Case has to be in one of the "4" settings (obviously) and the hubs should be locked.

My question is... what if the hubs aren't locked? Do the front wheels still get driven, but the diff is open? Or is power being applied to the front diff, but it doesn't make it to the wheels?


THanks for helping me understand what's going on up there... (it snowed last night)

 

[DriverSideImpact1008]

Power goes to the front diff. but the wheels are not being driven.

Conversely, if you leave the hubs locked-in and the t-case in 2WD, the wheels drive the axle and diff.

Here's a different way of explaining it including pictures...http://www.4x4abc.com/4WD101/hubs.html

 

[wired1000]

OK, that makes sense. Thanks!

 

[cheiser666]

I actually use the 4lo w/o hubs turned. It gives a low gear without the power being taken by the front and i dont loose turning radius.

 

[rlwm211]

Two things.

One, if you engage the front axle with the hubs unlocked and you are moving you risk damaging the transfer case

Two You can apply too much torque to the rear axle in low range without the front engaged and can potentially damage the rear end. This is less likely with the components of the CUCV being as heavy duty as they are but even so you should be very careful with how much power you apply to just the rear end.

RL

 

[cheiser666]

i use it for my friends switchback driveway that is a 20% grade. I agree it can prob do damage if left for long term use.

 

[reloader64]

What could be damaged with the transfer case in 4WD, but hubs unlocked?

Scott

 

[acesneights1]

What could be damaged with the transfer case in 4WD, but hubs unlocked?

Scott

4wd is meant for low speed operation so, it won't damage anything but if you drive it past 35-40 mph you are certainly not doing the front DS any favors.

 

[thecbldad]

Here is a shot of whats left of my transfer case after my son went on a little unauthorized field trip and didn't know how to lock in the hubs correctly.

 

[91W350]

I am lost, been messing with 4x4 vehicles most of my life, well, since 1968 anyway. All the locking hub does is disengage the axle from the front wheel. I do not understand how a minimal load of driving the front shaft and axles, but not the wheels would damage the transfer case.

Along the same lines, the full time 4x4s of the late 70s had very few drive shaft and axle troubles. The rotating shaft kept the slip joint from beating itself to death in one position.

I do not understand the broken case above either.

I moved a lot of heavy loads using low 4x4 with the hubs unlocked...especially while backing heavily loaded trailers uphill or in tight twists.

 

[Fleg]

4wd is meant for low speed operation so, it won't damage anything but if you drive it past 35-40 mph you are certainly not doing the front DS any favors.

4Lo is meant for low speed operation. Using your example in 4lo, it wouldn't matter if the hubs were locked or not. 35mph would do damage either way to the transfer case.

To answer reloaders specific question, nothing. The transfer case doesn't know if the hubs are unlocked or not, it just turns the front and rear driveshaft in 4wd both high and low range. You can overspeed a transfercase in 4lo and cause damage pretty easy but that has nothing to do with the hubs.

If (and I'm sure someone will) posts that they heard from a cousins, friends, brother that their buddy was driving in a 4wd without the hubs locked and something drive train related broke then I assure you, the culprit was something else.

 

[Cucvnut]

if you cant drive with hubs unlocked and the T case in 4 high what are auto hubs for ? who ever said you cant drive with a t case in 4 high and the hubs unlocked is wrong.

 

[DriverSideImpact1008]

Yeah, I'm not sure where this thread strayed so much.

Wired1000: To sum it up...again... Basically, don't drive like a fool.

Lock the hubs and drive normally if snow or mud is in expected during your driving. Then engage 4-Hi when you need it.

Don't drive in 4-Lo (regardless of hubs being locked) at more than 25mph or engage it while moving.

You can use 4-Hi or 4-Lo if the hubs are not engaged.

However, driving with 4-Hi engaged or having the hubs locked for excessive periods of time will both cause more unnecessary wear and more drag/less fuel economy.

 

[joediveguy]

Power goes to the front diff. but the wheels are not being driven.

Conversely, if you leave the hubs locked-in and the t-case in 2WD, the wheels drive the axle and diff.

Here's a different way of explaining it including pictures...http://www.4x4abc.com/4WD101/hubs.html

Good stuff!

 

[rlwm211]

If the hubs are DISENGAGED and you try to shift into 4x4 while moving you can damage the synchros in the transfercase. That is one way to damage the transfer case.

Another is that if you use LOW RANGE without the hubs engaged you can damage the rear end, possibly the transfercase as well. LOW RANGE is a torque multiplier and it is easy to exceed the design limits of a drivetrain by rough driving techniques while in low range regardless of the hub selection. By DISENGAGING the hubs you amplify the torque available to the rear end and this can be many many multiples of what the engine can produce alone.

The early jeeps with the two shift lever transfercases were never conceived to have lockout hubs and the designers set them up so you could not engage low range without the 4x4 lever engaged. This is for the same reason as above. I have know of people who broke a rear axles shaft while off roading and I would think that all that torque applied to the same shaft without the front end taking some of the load would be far more likely to snap an axle shaft.

RL

 

[saddamsnightmare]

December 19th, 2011.

To the OP:

Driving your truck up that 20% grade in FWDL without the front hubs engaged is a very poor practice and dangerous to the truck in any case. The system was designed from day one that when in FWD the front hubs are locked, the reasoning being power will then flow equally from the transmission to both the front and rear axles almost equally. Almost none of the FWD's you gents are used to driving are inherently true FWD's that is, intended to be driven on hard surfaced roads in FWD without snow, ice or rain to act as an equalizer, e.g. there must be an ability for either the front or rear wheels to slip (limited) to equalize any difference in tire diameters or other factors. And without true locking differentials, very few FWD's as we know them are FWD's, they are more like two wheel drives X2 as the power will go to whichever wheel slips first.
By comparison, the Unimog was built from day one as a true FWD truck, but in FWD unlocked (eg, differentials unlocked-hubs are always locked) the truck will behave like your FWD's, but when the differentials are locked, all four wheels must slip for any wheel to slip, hence a true FWD. They are not noted for short turning radiuses, and they cannot be driven on the pavement in either FWD or Locked FWD if the surfaces are dry, as the transfer case and axles multiply the engines torque so greatly that something will have to snap. A S404 will in L range-1 (either 2WD or FWD) have the engine turning about 175 RPM to 1 turn of the wheels, if fitted with the auxilliary 4 speed extra gearbox- give 8 gears in low range instead of 2, in L1L the engine turns 368 RPM to one turn of the wheels. With that amount of power applied, even a Unimog can have troubles if foolishly driven. If you want your CUCV to be around very long, drive it like a sane sensible driver, use FWD where needed, otherwise 2WD

 

[cheiser666]

I moved a lot of heavy loads using low 4x4 with the hubs unlocked...especially while backing heavily loaded trailers uphill or in tight twists.

Im with you!

 

[TommyM]

I think the risk is not in having the t-case engaged with the hubs unlocked.

Rather, the risk is ENGAGING (moving the lever) into 4x4 with the hubs unlocked and the front driveshaft/diff/axles not turning, while the vehicle is at speed. The shock on the t-case of slamming the front rotating parts from zero rpm to 2000+ rpm in an instant can't be good.

It shouldn't hurt anything to drive in "2-low," so long as you shift while stopped.

 

[cjtroutt]

Power goes to the front diff. but the wheels are not being driven.

Conversely, if you leave the hubs locked-in and the t-case in 2WD, the wheels drive the axle and diff.

Here's a different way of explaining it including pictures...http://www.4x4abc.com/4WD101/hubs.html

Ditto Ditto

 

[rizzo]

I have a M1008 with a twin stick NP205 in it and 40 inch boggers. I drive around in 2 low all the time. Lots of guys do. I have not broken anything yet.