old school locking hubs...

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crw

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On wintery days like this I end up driving my 1986 Ford F-150. This vehicle has locking hubs which, you have to get out and move the selector in the center of the wheel from Free to Lock. I came of age when these were becoming "old tech", and I've often wondered how this system works? What is actually happening when I lock the hubs?
 
The hubs have splines and the axle has splines. When you twist the locking hub it extends/slides onto or retracts/slides off the axle splines; when extended it engages and creates a direct connection between the axle and hub. When it's retracted it's not connected to the axle, so the axle spins independently (or doesn't spin at all) of the hub.
 
So when I have the hubs locked, but move the lever in the cab back to 2wd, my front wheels are turning the axles even though they are disengaged..?
 
You have a bunch of "stuff" that connects the front wheels to the transmission, so that the engine can make the front wheels spin. The hubs connect the front wheels to all that "stuff." When you unlock the hubs, the front wheels are disconnected so all that "stuff" doesn't needlessly spin when you're in 2wd and you're not using the "stuff" anyway.

Here is the "stuff" I'm referring to:
four-wheel-drive-intro.jpg

You have a front driveshaft, front differential, and two axle shafts that go from the front differential to the front wheels. If you're just driving around in 2wd, you're not using any of that stuff. But if the hubs are locked, all that stuff keep spinning when you're driving, because the front wheels are spinning and the front wheels are connected to all that stuff. So you unlock the hubs to disconnect the wheels from the front driveline, which saves gas and wear and tear on those components.
 
Originally Posted By: crw
So when I have the hubs locked, but move the lever in the cab back to 2wd, my front wheels are turning the axles even though they are disengaged..?


Yup! Some folk screw the hubs in come November and undo them in April. It's slightly more drag/ rotational inertia.

I had to tighten the wheel bearings on my 1994 b4000 with old school hubs; if you watch the youtubes about such things you might get a greater understanding.

TL;DR, there are dozens of round doohickeys that come off. Some torque to 200 ft lbs and some to finger tight minus 1/8 turn.
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Originally Posted By: crw
So when I have the hubs locked, but move the lever in the cab back to 2wd, my front wheels are turning the axles even though they are disengaged..?

Correct. There's no harm in driving around with the hubs locked and in 2wd (my Ranger has no way of unlocking the hubs, they're "locked in" permanently), it just might put a little more wear and tear on those components and might reduce gas mileage a little.
 
Originally Posted By: crw
So when I have the hubs locked, but move the lever in the cab back to 2wd, my front wheels are turning the axles even though they are disengaged..?


Yep. Many trucks have full time hubs. The front wheels are constantly spinning the front axles and differential.

Make sure your front hub system is in good condition if you are going to leave the hubs locked but transfer case in 2wd. Many of the lock in hubs are neglected, broken, leaking, bad seals, etc. I kind of prefer the full time hubs since they are always getting spun, always lubricated, and generally more reliable.

Your hubs are really easy to rebuild, clean, replace seals on if you get a hankering.
 
In 1976 I bought a Jeep CJ-5 and the first day it snowed I tried to lock the front hubs, but I had so little leverage trying to turn the hub via my fingers in these little indentations that I gave up. Drove for 10 minutes and things had warmed up and I could engage the hub.
 
My last truck with hubs was a 1969 F-150. Every once in awhile I wish I had hubs again. Occasionally I would use low range without the front engaged. I still use low range on dry pavement when backing a trailer up a steep hill, I just don't make sharp turns.
 
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So when I have the hubs locked, but move the lever in the cab back to 2wd, my front wheels are turning the axles even though they are disengaged..?


This is why I actually removed my "auto" hubs and put in manually locking ones. I use 4wd so rarely, I would rather have the MPG boost and reduced wear on my axles/CV/CV boots/etc. I got some take-off hubs from an older model. I have to get out now to do it, but I do less maintenance over time and get a little better MPG, and also lighter steering.
 
Auto hubs are supposed to, umm, automatically unlock when they detect that the wheels are seriously outrunning the front axle because the transfer case is in 2WD. They are not the same as locking hubs that are locked all the time.

The big downside is that the truck has to actually roll forward some before they will re-lock and give you 4WD. This is a problem if you are already stuck.
 
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Are these supposed to be engaged before the wheels slips? Like an "on the fly" Jeep?

I was at a junkyard a few weeks ago. The son of the guy running the place got a 4x4 ranger with locking hubs stuck. He wasnt the best at driving a stick so he had me attempt to get it out, but the truck was already stuck before we engaged the hubs. Lots of grinding.
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He didnt care. The poor girl burned oil and had a bad head gasket. Lots of white smoke.... Wont go into how high the RPMs went when I was trying to pop it out of place.
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How many kinds of hubs were there? Manual ones (with a quarter-turn knob), and non-hub (axles always turning); then there are the auto ones that took like two wheel revolutions to lock (so you better engage 4WD *before* getting stuck!). Any others?

Wouldn't be surprised if there were several kinds of auto hubs out there (electrically operated, vacuum operated, one needs 2 revolutions, one is instant).

I know on my Tundra, the axles are always live. But inside the differential there is (I believe) two clutches. One disengages one axle from the differential, and the other disengages the driveshaft. So the diff spins but the spiders do not; and the driveshaft does not either. [It's possible there is only one clutch, the driveshaft clutch; been awhile since I looked at the manual.]

I had a Subaru years ago where the rear axle shafts were always live, as was the rear driveshaft (2HI was really FWD). Engaging 4WD simply connected the two driveshafts together.
 
I'm a big fan of manual hubs. Nobody messes with hubs much, and the auto hubs can get stuck-up or balky after a while. I don't like to spend gas money on spending extra components when not needed... on a 97 pathfinder I used to drive it was a full 1-2 mpg penalty, and that thing certainly wasn't a full size. Manual hubs are easy to use, and it takes 30 seconds if you're expecting snow to engage them before the day starts.

For me, back then I was driving 450 miles per week. They paid for themselves in under a year.

The cost of spinning all of the subaru AWD components was 1 mpg. At least back in the day when you had a choice between 2wd and 4wd. the cost for the rear wheel drive and t-case was 1 mpg. That figure was remarkably low compared to the other mid and full size offerings.
 
I prefer manual locking hubs. I don't mind having to manually lock them, and they are in my experience very reliable. You also get the benefit of no wear and tear on front end components and better mileage when unlocked.

My mom's 1994 Explorer had automatic locking hubs, which have a reputation of being unreliable. They lasted a good 19 years before we started having problems with them, but 4wd wasn't used that much on that truck. Instead of buying new (expensive) auto hubs that were still unreliable, I converted it to manual locking hubs for less than half the price. Way cheaper AND way more reliable, it was a no-brainer. The hardest part was training my mom on how to use them.
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My 1994 Bronco also has manual locking hubs. I'm not positive, but I believe it originally had auto locking hubs when it was new and the previous owners converted it to manual, likely for the same reasons I converted the Explorer.
 
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