Hey y'all!

First off this is a 2000 F-250 Super Duty with 350k... So she started making this draggy grinding really quiet noise about a week ago. So little you could only hear it at about 5 miles an hour, and really never smelled, smoked or even made the truck noticeably slow down like brakes, so I thought it might be a problem with the hubs or lockers. Anyway, even thought the 3 other people I asked to listen said they couldnt hear it, it was driving me nuts so I went into the brake system. This truck has had 6 sets of rotors and pads in its life, 3 sets of hoses, and wheel bearings 3 times. It's had 2 sets of wheel bearings and 2 brake jobs (one with new hoses) since I've owned the truck for the past 4 years. I had the mechanic go over it with a fine toothed comb last time I had them done and he swore up and down there was nothing wrong with it, and that this amount of wear was very common on a lot of the 7.3's that come through. His shop works on all Diesels, but they seem to mostly work on the Fords. A lot of 7.3s and 6.0s through there, so I figured he knew what he was talking about. Plus I've used that shop since they bought it in 2017, and before that I used the same shop but from the Original Owner. After the brakes started dragging, I decided I'd tear the truck apart myself. The most major thing I found was that the HydroBoost was leaking like crazy from.... everywhere... I am obsessive about checking fluids and everything, and I've never had to top off power steering OR brake fluid. So I pulled the HydroBoost and Master Cylinder and just rebuilt them both just in case. The rest of the braking system seemed fine, other than a couple of busted hoses that I also replaced. Caliper Pins were a little stiff, I probably will pull them tomorrow as well. Otherwise the truck's brakes seem fine. So I continued looking into other culprits that could be making the brakes wear out. Suspension sqeaks and creaks like an old cellar door but all the joints move well and are greased. All checked out. I checked the Power Steering side too, and I could've sworn I saw fluid coming from the motor casting of the pump. Now, the cap on mine does not fit tightly and will slosh out some fluid if its high, and I had just added some to take it to max fill to see if it would fix my problem (it didn't). I wiped it off and everything and I swear a very small amount of fluid was coming from that pump. However, I am a plumber by trade and residual fluid can make you think a lot of things are leaking, so I decided itd be very unlikely for the pump itself to leak right out of the casting where the motor sits. Finally, I checked out the 4WD side (Vacuum Pump). Lots of problems with it. I vacuum tested it and all the lines, and only 1 of the lines passed. So that got me thinking about the 4 wheel drive. If I understand correctly, when the vacuum pumps gets to a certain amount of Mercury per inch, it cuts off and that sealed vacuum is what keeps the hubs unlocked. My hub seals leak tremendously, so my question is are the hubs always at partial lock (or Auto like it says on the hub), and if they are is that not doing some damage to something? I was always told not to drive around with your hubs locked even with Electronic 4 wheel drive, but that doesn't mean that's right. I'm not saying this has anything to do with the brakes and wheel bearings and stuff wearing out prematurely because I'm not a mechanic by trade and I don't have the diagnosing knowledge or full understanding of how total systems work together. I know in plumbing a problem with one system is often caused or exacerbated by another, so that's kinda what I'm going off here. My other question is, should that thing that looks like a lid that has the gasket under it on the side of the Vacuum Pump be airtight? I would've thought it would have to be to create vacuum, but I could'nt find anyone else who asked it. I'm pretty mechanically included, I had the HydroBoost, Master Cylinder and Vacuum Pump out in about an hour, and the Master Cylinder and HydroBoost rebuilt in a couple. I can do most of the work on these trucks, just limited by time because of work, and the lack of repeated experience doing it.

In conclusion:
Does the lid like thing on the Vacuum Pump need to be airtight
Are my hubs always partially locked
If they are is that okay
Could the partially locked hubs at all contribute to premature wear of pads rotors, calipers, wheel bearings and hubs.
Is this amount of wear normal? My previous 7.3 NEVER had those problems
Is it common for the Power Steering Pump to leak from the motor casting?

Anything y'all can tell me would be appreciated very much. THANKS SO MUCH -Rob

 

The vacuum pump is set to always maintain a certain level of vacuum in/on it's reservoir. If the key is on the pump will run if need be, so if your pump isn't constantly running than it's fine and the lid thing is fine.
The hubs are actuated by vacuum but their at rest position is unlocked. So any leaks will only become an issue when your try to use 4wd. This is where the manual function of the lock out would have to be used to lock the hubs and engage 4wd.
The excessive wear is most likely caused by the stiff slide pins you mentioned. These model trucks are notorious for slide pins getting dry and binding causing the brakes to drag and wear out parts.
I wouldn't call the wear normal because if the pins are greased often, say every other oil change, then the life of the brake parts goes way up.
It is common for everything in the steering system to leak at some point. Everything about the steering on these rigs is a joke. From the weak gearbox, to the pitiful undersized pump, and the **** poor routing of the hoses. Which is why a lot of folks end up modifying the system in some way to try and take up some of the slack Ford left hanging.

 

No, thats the newer trucks. The F150 have what they call 'Integrated Wheel Ends' (IWE) instead of hubs.
They are normally locked, and vacuum pulls them unlocked. I don't recall if they will remain unlocked without vacuum or not.
I'm not sure whats on the newer Superduties, but the vacuum actuated hubs on your truck use vacuum to switch between modes, not to hold in that mode.

I would be very surprised if yours still work via vacuum at all. I always treat mine as manual hubs.

If they were engaged, or partially engaged, that wouldn't add any wear to the brakes. Maybe some accelerated wear on the u-joints and front driveline, but thats about it.