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Truck 4WD Grinding or Not Working Quick Fix For Auto Locking Hubs

Created on: 2020-01-16

If you have a vehicle equipped with automatic locking hubs, and sometimes they don't engage, or grind when they do, try out this easy diagnostic.

Tools needed

  • Jack Stands

    Floor Jack

Hey everyone, Sue here from 1A Auto and today we're going to diagnose four-wheel drive inop. Not not working, but intermittently working. To do a quick diagnosis I don't want to go deep into electrical, I'm just gonna go right for make sure I vacuum out my vacuum actuators and make sure that my four-wheel-drive motor is working at the transfer case. So I'm going to have Lynnster [SP], Lenny give, me a hand because you want somebody up in the vehicle so they can put it in four-wheel-drive and you can check for vacuum and make sure that actuator is clicking in and out. Let's go.

All right, so now we raised the truck up on a lift. So at home you gotta think safety, safety, safety. I can't say it enough. Jack stands, make sure they're sturdy because we're going to start this vehicle and put it in four-wheel-drive so that the wheels can spin, so I can be underneath here. So I have a jack, it's locked in on the locks. At home, just do what you know is safe. So we're going to start her up. And this is the vacuum actuator at the back of this hub. And this is the vacuum line going down in there. So when Lenny puts it in four-wheel-drive high and then he's going to let go of the actual brake and let the wheel spin. Now, it's working at this time. So is this one. So four-wheel-drive is working but that tells me that I've got a vacuum down here. Electrical's working, the four-wheel-drive motor on the transfer case is working, 'cause I got four-wheel-drive. What can make this intermittent? Well, that hub not being able to come in and out will make this intermittent. I know I have vacuum because it's working right now. Is my vacuum hub actuator faulty? Possibly. What does that connect to? It connects to the outside of that shaft, the CV shaft, and it has a nut that goes on it. And those are notorious for loosening up. Even though you torque them, they loosen up. Lenny, put her in neutral. So what we heard earlier was a growl noise out of this wheel. So that's why I know the problem is over here, and not at that one. It sounded just like two gears trying to go together but not lining up. That noise tells me that the shaft is not engaged. So we're going to lower it, take this wheel off and check for that nut loosening.

So once you take your wheel off, you have the wheel that was making the noise, get this little cap, I just take a pair of open pliers, just wobble it back and forth and pop that cover off. You don't ever want to put holes in there 'cause you don't want water and grease getting there. That should not do that. So now we're going to look up the torque spec. I'm gonna take this off, make sure there's no damage to the threads. And there's no damage. I'm gonna re-torque it and let's see if it holds. So it's a 13-millimeter socket, just gonna put it on it, and it's so loose I can do it by hand. And we'll check the threads out, both the nut and the end of that shaft. Looks actually really good. Think it just came...just backed off, that's all.

So now that I know the shaft threads are good and the nut threads are good, I cleaned them up a little parts cleaner. I'm gonna put some red Threadlocker on there. I'm just gonna hand thread it. And then I looked up the torque specs and this nut is 20 foot-pounds. So we're going to torque that. Make sure that this is centered. The axle feels like it's in the threads. My torque wrench, 20 foot-pounds, tighten this thing down. Might need a pry bar. It's just 20 foot-pounds but see if I can use these pliers. Now we're going to reinstall our cap. Make sure it's not damaged. It's nice and round, it's not oval-shaped. Give it a little tap. You wanna keep water out of there the best you can. We'll put the tire back on and check it out.

We did it, 2011 Ford F150, quick diagnostic. No need to go into the electrical, no need to go through any books. Just use a little quick, common sense. What causes this to work? You can look that up real quick and know that it's vacuum operated. They're not locking hubs. So the first thing you want to do is, intermittently, that means that everything seems to be working in line but what's stopping it that couple of times it doesn't work? Check for vacuum. Check for power. Motor could be intermittent, or vacuum hubs, or vacuum could be intermittent. We had vacuum, we had hubs spinning at that time, then we heard the growl. Quick fix. Hope this helps. Have fun.

How to Replace Four Wheel Drive Switch 2001-02 GMC Sierra 2500

How to repair, install, fix, change or replace a transfer case shift motor that is not working, engaging or is defective on Chevy Silverado and GMC Sierra, 2500 and 3500, model years 01 and 02.

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