Lazy Daze Owners' Group

Operation of E450 parking brake

April 28, 2024, 07:06:55 pm

Larry W or someone else.  About the operation of the older Ford E450 transmission mounted parking brake.  Does the ATF operated brake need fluid to keep the brake off? Or does the foot pedal provide fluid to operate the brake on?   If fluid were to slowly leak out would the brake shoes inside the drum start rubbing? Could the friction surfaces wear away slowly enough that it would not stop the vehicle after awhile, even when applied?
    Curious about a friend's non operational parking brake.
    (My '99 E350 has 'top hat' type brakes in the hubs of the rotor, like many cars have.  They need new lining's now and aren't adjustable.)  RonB

Re: Operation of E450 parking brake

Reply #2 – April 30, 2024, 08:42:28 am

Hey Ron,

I am not quite sure what specific information you are looking for. IF your friends transmission mounted parking brake is not working, my belief is that the problem is not likely from the lack of the transmission fluid. The transmission fluid, to the best of my understanding is to keep the components in that drum cooled down. If I am incorrect, I hope someone more knowledgeable will clarify that.

But, if the transmission fluid leaks out of the transmission mounted parking brake, it could damage the parking brake and possibly the transmission. You do *NOT* want to drive with that reservoir dry!

I may have been one of the first Lazy Daze Owner's to have had my transmission mounted parking brake rebuilt. Our 2003 rig was 6 years old and had 76,000 miles at that time. As I recall, Larry W was interested in the parts that were used and I think he was curious about examining a failed unit. I very much appreciated Larry's attention to this matter. The leak was evidenced by a small drop (around the size of a 50 cent piece, remember those?)  of an oily substance on the driveway below the parking brake drum. There was also some fluid on the bottom of the drum. I have no idea why my unit leaked; there was some speculation that driving the rig with the parking brake activated could heat up the brake and cause the leak. Consequently,  some folks were installing parking brake alarms to remind them to release the brake before driving. That was definitely NOT the cause of my parking brake leak since I NEVER use the parking brake.
 
I am not sure I answered your original question. If your friends parking brake is leaking, my understanding is that as long as you can top off the fluid (not an easy task) it would be safe to drive until the system could be repaired.

Steve K

Re: Operation of E450 parking brake

Reply #4 – April 30, 2024, 01:57:45 pm

Hi Larry, Good pictures, I must have missed them. So the brake drum and linings are dry.  How does this 'few ounces of ATF' get into the roller bearings?  I also can see the splined slip joint. Is there an eccentric cam to expand the brake shoes?
     My friend says that his mechanic takes care of everything. I'm hoping that includes this few ounces of ATF. But he has no operation of parking (emergency) braking. At 180K miles, maybe the cable has stretched enough and lining thickness has decreased, and that he just needs adjustment; to engage the friction surfaces when the brake is applied.  No 'star wheel' to adjust?
   He lives in flat land, so really doesn't need, and may not use the parking brake often. Here in San Diego, almost nothing is level, so Parking brake use is always needed. The expense of replacing a parking pawl is very high compared to having the parking brake applied. (my Lexi automatically apply and release the parking brakes).
     A little story: where I worked 19 years the parking lot was very  unlevel and a fellow worker would slam his Volvo into park while still moving a bit!  He didn't customarily use the parking brake.  (Software guy, and apparently not much  mechanical knowledge).  I warned him that all somebody else had to do was nudge his bumper and the car could go rolling away!  But he did it to himself. One stop many days (weeks) later and the pawl broke, pieces got into the transmission, several thousands of dollars and a week or so of repair (a rebuilt tranny?, hard to find in the early '80's). I don't know if he started using his parking brake then. He wouldn't talk about it to me.     RonB