grinding noise while driving?
gain access to the front of each side of the drive unit, each side should have an oil level plug in the front of the axle housing, remove the plug to check the oil level, if low add oil till it runs out of the plug hole. Use clark part number 2794022.
As for the brake pedal going down and no brake action?
check the master cylinder reservoir located in the steering column cowl, there should be a hole exposing the reservoir so you can see the level, if you can't see the level then remove the steering column cover and access the reservoir that way and make sure there is fluid in it.
If there is no fluid or it is low you'll need to check for leaks at the master cylinder located under the floor plates, also check the brake calipers located on top of the drive unit in the middle of the drive axle where the disc's are.