Recently I pulled a car out of the ditch while in 4 low........I thought by doing so all 4 wheels would be locked and turning..........However this was not the case only 1 in front and 1 in back ( obviously in snow/ice conditions).

If this is normal than a) why have 4 low and B) how can I lock the diffs.............BTW the hubs were in manual ''lock'' position.

Thanks in advance for advice !

 

It sounds like you have open differentials and not lockers or limited slip. You would have to check the axle code in your door sticker to confirm this. If there open diffs the only fix is new differential equipped with a locker.

 

Sounds as if both of your axles are Open Differential axles.

Your front is definitely an Open Diff since that is the only way they come.

With an Open Diff in a low traction situation all the power is sent to one wheel (the one with the least amount of traction). That's why the rear axle can be optioned with a Limited Slip Differential. Ford uses one that when the axle "senses" that one wheel is loosing traction, the clutches engage to spread the power between both wheels.

Disclaimer: that was a VERY basic explanation. Head over to www.howstuffworks.com for a more detail explanation.

There are many types of traction aids out there you can put in either or both axles.

BTW, it is a myth that an Open Diff only sends power to one wheel. When there is equal traction power is split between the two equally. However, once one loses traction, all the power is sent to that one wheel. So you have 4WD but only when you have traction.

 

what are the benifits of having an open diff and the disadvantages of a limited slip diff?

 

I'm no expert, but here is what I think is happening.

When you select a 4 wheel drive position on the indicator you're telling the transfer case to send power to both the front and rear differentials. “Spin both front and rear drive shafts” as it were.

When you select 4 low, you're telling the transfer case to use the low gear ratio intended for "pulling conditions" resulting in higher torque, but lower maximum speed (as opposed to 4 high which is intended for more normal "driving conditions"). Neither of these options inherently "locks" the differentials.

Whether or not the differentials lock up is strictly determined by the fact that you do or don't have locking (or limited slip) differentials - so yes, wheels can spin.

My guess is that you either don’t have LS or locking diff’s, or the snow/ice was so slick that it didn't allow the lock. Many other posts here (referring to the rear LS diff.) say that you need at least a little grip for the LS to work. So they suggest gently applying the brakes, while applying the gas, to engage the LS.

I don’t know how to engage a “locking” diff. since I don’t have one.

I don’t know if the transfer case is designed such that it can deliver all of the power to a single slipping wheel when in 4x4 mode – but that would seem to be a really bad design. I don’t think so since that behavior is usually associated with a planetary gear system – which I don’t believe is how the transfer case works.

 

Sure would! Now systems that allow the opposite: all the power to the one wheel with traction is what would be cool. You'd need a different type of transfer case and LS units (minimum) in both axles (ala Jeep Grand Cherokee with Quadra Drive II).

Good call on the brake application. Sometimes a bit of brake does indeed help that rear LS unit lock up in situations like you describe.