Every so often the inevitable happens and we unintentionally incur a bit of damage to our beloved 4WD vehicle. We could be attempting a really challenging incline with tricky obstacles. Perhaps we are enjoying a rock crawling trail with a few mates and after multiple unsuccessful attempts at choosing the correct drive-line, we decide to just give it the boot with a proper full-send. You give it gas and all you hear is a loud metallic popping/snapping sound…BANG!
What could possibly have gone wrong? Yip, the drive shaft broke clean-off right at the yoke! Well, what now? You need to get home to have the vehicle repaired but you are out in the mountains on a 4×4 trail and mechanical assistance could be miles away?
Can you drive a 4WD truck without a front or rear driveshaft? Yes, this is possible, if you drive a traditional 4WD with a lockable center differential. Remove the damaged drive shaft and lock the center differential. This will allow the transfer box to transfer power to the front or rear driveshaft. You will be able to safely drive the vehicle in front-wheel drive or rear-wheel drive mode. A few warning lamps from the ETC system might start flashing but don’t panic.
Driving with only rear drive shaft
In the event of an emergency situation where you are having to drive your 4WD in rear wheel drive mode, there is no risk of axle binding. There is also no risk of shredding pinions or gears when on dry ground. IF the front driveshaft has been removed due to damage or failure and you have the ability to lock the center differential, there will be no difference between the front and the rear differential action thus no risk of binding. This is due to the fact that no force is being applied to the drive train due to differences between the front and rear drive shafts.
Certain internal components of the differential might be under slightly more load, however, this is perfectly safe as long as you adjust your driving style by not speeding or driving like a maniac, you should be okay. This is a fantastic way to reach help when your front drive shaft has blown out, and one of the advantages of driving a 4WD vehicle. Remove the damaged drive shaft, lock the center differential and carefully drive off in 2WD rear wheels only, to find assistance immediately.
Driving a 4WD truck without a front drive shaft
Driving a 4WD without a front drive shaft is quite safe. Part-time 4WD’s have 2H which is meant to be engaged only when driving on dry surfaces with high traction. Driving in 2H also returns the best MPG
(GOOD READ: How 4WD Affects Gas Mileage).
Most 4WD trucks have a center differential that can be locked. This mode engages the front drive shafts once the vehicle is placed in 4H mode. Power is then distributed evenly between the front and rear drive shafts. However, under normal high-traction dry conditions (like a highway or dry pavement), the vehicle should be set to 2H which does not engage or propel the front drive shafts.
AWD vehicles are a different ball game since the power is permanently transferred to both front and rear drive shafts. Most AWD do not allow you to lock the center differential, thus not giving you the option to force the power to either the front or rear drive shafts.
What Is A Slip Yoke?
The slip yoke is a very important component of any drive shaft assembly. The slip yoke assembly allows the drive shafts to flex or “slip” with their given application. The slip yoke is also essential for allowing u-joints to rotate properly with the drive shaft.
INTERESTING READ: U-Joints & the Funny Sounds They Make
It is extremely important to keep the slip yoke lubricated on your 4WD vehicle. Have them inspected with every major service to ensure they are still firmly seated. High levels of stress will occur along the drive shaft due to dry slip yokes or dirt filled lubricants. The drive shaft could also snap off at the yoke due to metal fatigue or old age since these components have a life span. If you often drive off road and fail to regularly inspect and lubricate your slip yokes, this will result in severe damage to the drive train when you least expect it.
Can An AWD function without at front or rear drive shaft?
Most traditional AWD do not function like a 4WD where you can disable a drive shaft. If you drive an AWD with an open center differential that cannot be locked and has traction control, this procedure will not be possible. AWD do not allow you to drive the vehicle in Front Wheel Drive Mode or rear wheel drive mode only. You may however run into other problems, depending on which model vehicle you are driving and if the rear drive shaft of the vehicle uses a “wet slip yoke” to connect to the transfer case. Removing this wet slip yoke will result in oil pouring out of the transfer box while you are driving which will seize up the transfer box.
Can You Drive A Truck Without A Transfer Case?
If you are driving a 4WD vehicle then all the power is sent to the drive shafts to the differentials through the transfer case. Without a transfer case, you will not be able to drive the vehicle since the power is split 50/50 to the front and rear drive shafts and in 4WD or 4H mode. Alternatively 100% of the vehicle power is transferred to the rear drive shaft and differential from the transfer case when 2H mode is selected. Hence, without a transfer case, a traditional 4WD vehicle cannot drive.
Driving a AWD without a Rear Drive Shaft
This is not always possible since AWD does not function the same as a FWD – READ more about AWD vs 4WD here. IT also depends on your AWD transfer case, however, you cannot disable an axle on a AWD vehicle. If you disconnect drive shaft to the rear axle the car will not move. That is because the center diff cannot transfer 100% of the power to the front drive shaft, so it will move until the viscous coupling loses all ability to resist shear. This will happen in a matter of seconds.
Also, if you remove the rear or front drive shaft from the transfer case you will lose transfer case oil. IF you do get the vehicle to drive, depending on what AWD setup you have, you might also experience violent vibrations coming from your drive train after a certain speed since the system is not balanced anymore.
AWD and permanent 4WD vehicles make use of a Viscous Coupling. This component does have the ability to not lock up. The function of the viscous coupling is to allow speed differences between the front and the rear drive shafts from the center differential, not as a coupling to transfer power to the rear.
If we use a Subaru AWD Manual transmission as an example, the drive shaft is directly connected to the center diff. Power has to go through it to get to the front or rear wheels. If the viscous coupling gets damaged the center differential is open. This means it won’t transfer any power to the front if the rear wheels aren’t connected.
Driving a 4WD with the center differential locked and the front or rear drive-shaft removed will get you to safety without much drama. Provided the transfer case doesn’t use a type of viscous coupling between the front and rear as in the case of a permanent 4WD and AWD. This component could heat up to damaging temperatures when there is a speed difference between the two. This means your transfer case will effectively destroy itself.
Or the vehicle just won’t move forward in the case of an AWD since there is no way of locking the center diff.
Bottom line is, have the vehicle fixed as soon as possible. These 4WD and AWD systems are highly engineered and designed to function in a very specific manner that allows power to be transferred equally and safely to drive shaft without damage. Do not attempt to continue driving a 4WD with the center differential locked for longer than necessary. Look after your 4WD and it will look after you!
Happy 4 Wheeling and remember, Safety First!!!