2002 F250. 7.3 4x4. Randomly makes high pitched whirring sound for 1-3 seconds. It goes away if I put it in 4x4. I thought it was bad auto hubs so I replaced them. Still happens. Replaced vacuum lines from frame to hub. Fixed for several hundred miles. Now started again. It also feels like it slows or lurches a tiny bit when it happens. It also seems to go away when I don’t use the AC, but it did still do it once. I thought maybe it was a failing vacuum pump, but it doesn’t have the usual symptoms. Any guesses? Thanks.

 

Kind of sounds like the fan clutch is engaging to cool the engine down. The cooling system on these trucks is so good the fan rarely ever kicks in fully.

 

Ever since I got my '02 7.3L Excursion repaired, I have not heard the fan kick in yet.
of course, have not pulled a load with it yet, but I have been driving in 90* heat up/dn our local hills.

the highest temp I have seen is 202* and the minute I top a hill, it drops back to 196-198

 

I live in AZ so my fan gets used regularly. I will check it out though.

 

Well if it isn't the fan you might check that the exhaust back pressure valve hasn't come loose from the actuator. That is if you still have one. Sometimes if the clip comes off the door can close itself, effectively becoming a Jakebrake.

 

I would bet dollars to donuts you need to grease your front axle stub shaft bearings located in the center of the unit bearing.

You can do this by removing the locking hub, snap ring and thrust washers, then use a grease needle to inject grease along the stub shaft to the bearing.

This really needs to be done periodically on all of these trucks and is something I do to almost every truck I work on - especially if locking hubs are coming off for any reason.

Honestly, the locking hubs SHOULD be removed periodically and greased (lightly) to avoid getting corroded and STUCK in place.

Another thing to consider is the condition of the knuckle seal/‘vacuum seal’. This is what locates the axle in the center of the knuckle. As it gets worn, it allows the axles to ‘droop’ in the knuckle. Eventually, the axle shafts will bind and spin even with hubs unlocked - carnage of the stub shafts will occur when the bearing I explained how to grease above is destroyed and damages the stub shaft. You can check the ‘vacuum seal’ (such a stupid name for this part...) by using a prybar to lift the axle at the u-joint, inside the axle ‘C’. It shouldn’t move more than 1/8” or so and should keep the u-joint in the center of the ‘C’. If there is a lot of play/droop here, the stub shafts, axle bearing and thrust washers may be damaged... Excessive droop will cause the axles to do a jump rope motion - often causing a strong vibration complaint.

I ONLY use Spicer parts for all of the above. Except unit bearings. I use cheap (Detroit axle lately) unit bearings and keep them full of grease - through the ABS sensor hole. I always fill every unit bearing I see with grease if the rotor is off for any reason.

 

If it does this while driving, then I agree with sky. It's the stub axle flopping around and the interior bearing in the unit is toast and locking up. The sound is the stub chattering around the rollers. Using the abs sensor hole grease method will not help as those rollers cannot be serviced like that and need the needle grease method. If you pull the bearing, you can check the rollers and shaft to see if it's the case.

I have had it happen twice before I realized it was due to lack of maintenance on the internal rollers. I would get a whizzing sound while driving and my warn manuals would slightly rotate twards lock. I replaced the bearing, the stupid little plastic vacuum plate/ring and lubed the internal rollers with the grease needle method and it's been good for a long time now. Luckily my stub axle was not chewed up.

 

I’m going to replace the wheel hub assembly, seals, and u-joints. Passenger side outer shaft is flopping around pretty badly so I’ll probably replace the outer shafts too. Might as well do it all once I’m in there.

 

Here is a good thread on the subject and grease needle procedure.
https://www.ford-trucks.com/forums/1...l#post16961300

 

Lost my hub inner seal, but luckily I always grease the hell out of that inner bearing. I’m currently stuck chasing other sounds, in a Napa back lot. Does anyone have a crossover dust seal number? Napa doesn’t carry it, maybe I can find it elsewhere…

 

There is no ‘inner seal’. When the knuckle seal (aka vacuum seal) fails, it spits out the outer ring. The dust seal on axle shafts just keep dirt out of the axle tubes.

 

You should take a ton of pictures next time you do this with auto-locking hubs and post them up in a step by step. You'd be the Axle King and everyone would appreciate your sacrifice and service. We might even put up a statue!

 

There are threads in the tech folder for each of these tasks. I’ve learned all of this stuff (and plenty I’ve already forgotten...) here over the years.

However, I’m literally doing brakes today on a NJ truck that was parked for the last 5yrs. We will be greasing the axle shaft bearings and filling the unit bearings with grease, etc. I’ll try to document all the things I typically do for a ‘brake job’ on these trucks....

 

Thanks. Be sure to link it here so we get notified if you make a new thread for it. I'm going to have to do this on my old girl soon and some detailed info will make it quite a bit easier. My google fu isnt as good as it used to be when I was a young fart.

 

Thanks for that clarification. I was dealing with a few different parts shops in Canada while dealing with a few issues, and one of them had the seal labeled as an “inner seal”.

main issue turned out to be the driveshaft support bearing ….. that the shop that repaired the truck said they had replaced 2k miles prior. They lied.

anyway, 2k miles later and she’s running fine in the lower 48.