Auto Locking Hubs explanation

129145 Views 24 Replies 14 Participants Last post by 97_7.3_4X4, May 30, 2015

wopr21

Discussion Starter · Jan 24, 2012

Ok Ive gone through a lot of threads here and cannot find an answer to my question.

I have a 2001 F250 7.3 Diesel. I just replaced both auto locking hubs and wheel bearings. All tested fine and according to my mechanic, all is working normally. I want to know if 4WD low engagement is the same as getting out of your truck and locking the hubs manually. If I have my hubs in the "auto" position, why do I still have to get out and rotate the hubs into manual. Some people are telling me that because of limited slip differential that I dont have full 4WD until I get out and change the hubs to manual. So my question is why have auto locking hubs if I still have to manually change the hubs.

It seems like I have half 4WD until I lock the hubs myself. Then its great. I've gotten stuck in snow many times thinking I have engaged 4WD when I haven't.
Its frustrating when everyone with 4WD is just plowing past you.

Thx anyone

wopr21

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BryceB

· #6 · Jan 24, 2012

whitextreme said:
Since the auto hubs only run off of one vacuum line shouldn't they be both be locked when the truck calls for 4 wheel drive if the system is working correctly? I didn't think that there was any difference between the auto and locking them if they work. Please shed some light on this if I am wrong.

Yes, both hubs lock. the dash knob is just a vacuum operated way of locking the hubs to the end of the axle and also shifts the transfer case. just locking the hubs manually does not put you in 4x4 becasue it does not shift the transfer case (the magic knob on the dash does that too). A full manual 4x4 set up, the transfer case would be shifted with a lever and the hubs would have to be manually turned.

Unless you installed a limited slip differential in your front axle, you don't have limited slip in the front, just the rear axle. AFAIK, LS was not an option or our trucks in the front axle. So forget about LS in your front.

Locking the hubs (either with the automatic vacuum method on the dash or getting out and turning the knobs) locks your wheels/hubs to the axles. the differential is still a differential. It does not lock the 2 halves of the axle together. The wheel with the least amount of traction will get the most power in an open differential type set up.

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BryceB

· #12 · Jan 25, 2012

wopr21 said:
So I guess if I'm going to need real 4WD , I'll need to plan ahead and lock the wheels manually. True?

wopr21

Incorrect. If your auto hub system is properly working, the hubs will lock.

If you have an open differential in the axle, power will go to the wheel that has the least traction. If you have a Limited Slip differential, power will go to both wheels until forces overcome the clutches in the LS differential then 1 will spin. If you have a "locker" in the axle, it will lock both axles together like a solid rod between the wheels and both wheels will turn. (OK, they can unlock when needed in a mechanical and when you turn them off in the case of an air or electric locker). None of that has anything to do with the hub locks (manual or auto)

to have true 4wd where all wheels get power, you need lockers or solid axle front and rear... but that's not very friendly on the street. That's why they have differentials... solid or locked axles cause both tires to spin the same speed on that axle and that's bad in turns because you need the outside tire to rotate faster than the inside or the wheel will slip on the inside (the chirp from an axle with a locker in a corner or sometimes a spin out). A no open or LS differential allows the tires to rotate at different speeds.

in the case of my truck, I have 2-3wd in a sense. LS in the rear that will hold both spinning to a point (1-2 wheels) and an open front differential that give me 1 more wheel with power. 3wd until the rear LS lets go and only 1 spins giving me 2wd. It's called 4wd becasue all 4 wheels can get power from the engine at times.

the reason for auto hubs.. so you don't have to get out and turn the hub lock.
why are there manual hub locks on auto hubs.. when they don't work automatically, you can get out and lock them manually and get unstuck.
Do you have to lock your hubs to be in 4WD? No, only if your auto hubs are not working or if you don't have auto hubs.
Do I get better 4x4 action or true 4wd if I manually lock my auto hubs. No (OK in some cases yes). In the case of No... If you hubs are locked, they are locked whether it's the internal auto lock working or manually.. they aren't doing anything but locking the axle to the hub. Locked is locked as long as they are not broken. In special cases, changing the direction of travel (forward to back, or back to forward) will momentarily unlock the hubs (my '97 Ford Ranger was like this). I'm not sure if our hubs work like this... if they do, then manually locking them will stop this moment of unlocking.

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