I recently bought a 99 f250 7.3 diesel and I love the truck but It seems like when I fix something, another thing breaks. Ill get to the soft grinding noise coming from under the driver's seat later, for now, I finally got all my vacuum lines fixed so that my auto hubs finally actuate but when I switch to 4hi or 4lo i get a whizzing sound from my tires then a loud clank before my 4x4 engages. and then while im driving in 4x4 it seems like the hubs dis-engage then I get the loud clank again and they re-engage. I just greased my hubs and they looked fine. someone please help me, I havent been able to enjoy my new truck yet

 

Does the AC default to defrost when this happens? Just replacing the vacuum lines may not have fixed all of the issues with auto hubs. There is still seals and Orings in the hub and hub lock mechanisms that could have slow leaks, and the pulse vacuum hub solenoid is known to go bad as well.

Did you service the hub locks at all when doing the vacuum lines?

 

I did the vacuum line check by turning on the vent and engaging 4x4, the air remained coming from the vent and did not switch to the defrost. THis tells me that the line is sound right? the o ring on the hubs seemed fine.

 

what are the hub locks?

 

That is a good indication, yes.

Hub locks are the actual mechanism that locks the wheel hub assembly to the axle. It's the actual part you turn in order to lock it in. Take a look at the "guzzle" link in my signature. He's got good information on how to service the hub locks and vacuum system.

 

thank you for your help

 

I did do the hub lock maintanance. more or less how guzzle does it. If i have too much grease on the hub locks, would that cause the problems i am having?

 

It's possible. I'm not sure about the whizzing but I've witnessed popping in the front hubs, especially when turning. Usually means the locks need servicing. Still not sure where the whizzing comes into play though.

 

the whizzing sound is more like the sound of a spinning roulette wheel.

 

Is everything turning the same speed, or is there slipping going on? If there is slipping, and the axle is rotating faster than the wheel, it could very well be you need to pull the hub lock out and check it over again. If it's allowing the same rotational velocity at the wheel, how sure are you that you aren't hearing the transfer case lock/unlock? It kinda sounds like what you describe. Maybe it's locking/unlocking intermittently?

 

That sounds like the hubs are only partially locking and the teeth aren't fully engaging and skipping on each other.

 

How dose that happen Jason? I too can feel mine lock and hard to drive on asphat, but say pulling out a stump, the front wheels don't turn. Been fighting this for a whole. I like the auto feature so I haven't wanted go to manual yet.

Chet

 

I am not really sure Chet. I think in his case he may have put too much grease in and they are sticking, but it is just a guess based off of his description.