The V-10 E-450s that come with 4R100 (4-speed automatic) have the parking brake assembly mounted on the tail shaft of the transmission. It has it's own oil supply, separate from the transmission. The parking brake housing contains 4 ounces of transmission fluid. If the brake assembly develops a leak and is not keep filled, the output bearing can fail. Originally the oil seal was not replaceable and the assembly was replaced as a unit at a cost of over $1000 plus labor. However, Ford now has rebuild kits for this unit. There has been more than one failure reported on the LWALDRV forum. It's worth checking occasionally. I often visually check the entire under-carriage for leaks and annually remove the plug to physically check for the fluid level. The plug is not visible from below without using a mirror or small camera. You must find it by feel. Once you have found the plug, it is fairly simple to remove the plug and to check the oil level.
You can see how to find the parking brake and check the oil level here:http://www.flickr.com/photos/lwade/6128666523/in/set-72157627503762313/
There is also a good article about checking the fluid level on the Technoz website that includes a photo of the fill plug.
By the time you notice drip marks under your rig,which are around the size of a silver dollar under the parking brake unit, it will probably be too late to prevent more damage. Those drips are usually caused by the parking brake unit becoming overheated........ and by that time you will probably experience damage to your parking brake unit like I did. But if you check the fluid level or have your servicing shop do it when they change your engine oil, perhaps you can prevent the overheating issue. Another cause of overheating this part is driving with the parking brake engaged.
Note: As noted above, Ford now has rebuild kits for this unit. When I was told my parking brake unit could be rebuilt, I was quoted a labor figure that included removal an the rebuilding of the unit which I thought would be a few seals and gaskets. Once the unit was taken apart, it was discovered that some bearings in the unit had overheated and needed replacing. Those weren't cheap either.
Here is the parts list and prices, all are Ford parts:
E8TZ-2L602-A......Bearing assembly 73.03
E8TZ-2L603-A......Bearing assembly 106.75
5534 Transmission to brake gasket 16.15
I think if I had caught my problem earlier, I would not have needed the two bearing assemblies. but who knows?
Check emergency brake fluid regularly.
Do not drive with emergency brake on.
Contributors: Larry Wade, Steve Kocan
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