4WD drive sytem help.

[Jim Hannah]

Hi guys,

I'm hoping some of the knowledgeable guys on here can give me a bit of a heads up on how this system works...I know it's operated by vaccum valves, though exactly how what or when I'm not so clear on.

Anyway, I've noticed that if my 3.2 NS is in AWD (4 high, but not locked), and I jack up a rear wheel, which I often do to check wheel bearings etc, the wheel is very stiff to turn (and yes, it is in neutral, with the handbrake off). It appears that I'm turning the rear diff and the central diff/transfer case too? When I switch to 2wd, and make sure it disengages from AWD, it becomes easier to turn, though still not exactly free, so I can't spin the wheel freely to listen for any roughness in the bearings, for example.

Is that all normal, or is something amiss?

Thanks,

Jim

[Kumabear]

Hey Jim

From my understanding the hubs and CV's are always connected so you it will always be turning the cv, dif and driveshaft.

When you place the car in RWD you are just disconnecting the front driveshaft from the transfer case so it will no longer be receiving power.


Because the hubs, cv's and driveshafts are always connected to each other regardless it means the whole drive train back from the wheel but before the transfer case is going to be moving.

In order to check for wheel bearing noise I was lucky enough to have access to a hoist, so i just threw it into AWD with the car on and used a big screw driver. You press the tip of the driver against the hub knuckle behind the bearing from under the car and press the back of it against your ear. You can then hear every internal noise its making, kinda freaky actually.

You could attempt to do the same with the car off on jacks but with the car in RWD ( to lessen resistance) then have a friend/helper spin the wheel as quickly as they can.

[Kumabear]

On a related note this is why we receive very little real benefit to ever driving in RWD.



There is virtually no fuel saving tho i do notice its a little quieter on the highway.