Driveshaft mounted parking brake fluid.

[Dualie]

I have a 94 F-Superduty (F-450) with a drive shaft mounted parking brake assembly. Originally ford called for Mercon/dex III.

Its a completely separate assembly manufactured by ZF for ford. It mounts on the tailshaft of the Trans like a transfer case but doesn't share any actual fluid with the transmission. Its completely sealed and divorced unit with just some bearings to lube inside. Holds like 3/4 quart of atf.

What fluid should i put in there? these things are over $1,000 if you have to buy an assembly from ford.

I'm R&Ring the trans for a reman unit from ford so its the perfect time to service this unit.

I have some older Redline Syn mercon dexIII that im going to use if no one else has any suggestions

 

[unDummy]

Any full synthetic Dex/Merc will be fine.
Redline D4 or Synthetic ATF are good choices.

 

[JHZR2]

So the bearings move when the drivetrain does? They get loaded to actuate the brake, and that's it? Is the unit sealed so that it is NOT servicable unless the trans is removed?

If you can drain/refill on the truck, I'd use whatever - you just want to exchange it every few years to get moisture out.

Redline is great, but unless there is some high load in there, not sure you need much of anything special. I'd mainly want to get moisture out now and again. Redline surely is great, but I doubt critical by any means...

 

[MGregoir]

It probably uses the same fluid as the transmission so if there is a seal failure, you don't get a dissimilar fluid in either unit and cause problems.

Match the transmission fluid.

 

[bdcardinal]

Originally Posted By: Dualie
I'm R&Ring the trans for a reman unit from ford so its the perfect time to service this unit.


Good choice getting a Ford reman. How recently did you buy it? The warranty was upped from 3yr/100k miles to 3yr/unlimited miles.

 

[Dualie]

The unit bolts on the back of the trans and power is transmitted right through it out the back to a U-joint yoke. Its basically a hub/drum brake mounted on the tail shaft of the Trans. Any time the drive shaft is moving the bearings are spinning.

It holds VERY little fluid much less than a quart, basically just an oil bath for the bearings running inside it.

there are some seals inside the unit to keep the fluid out of the drum assembly area. the drum is the parking brake for the whole vehicle, and even when adjusted and working at its highest level is barely adequate. I will snap a pic of it when i get the new reman Trans tomorrow.

since ford is no longer licensing mercon I'm going to assume the new Trans is going to be filled with mercon V. Maybe i should fill the brake assembly with merconV for simplicity's sake


As for the Trans I'm buying it tomorrow. The truck is 16 years old and only has 81,000 miles. the 3 year part is what sold me, that and no matter who installs it they will fix it @ any ford dealer in north America.

 

[Dualie]

Glad i changed it out, the former mercon in there looked like used diesel oil when it came out. BURNT! Hopefully it will like its new merconV fill.

 

[defektes]

Originally Posted By: Dualie
Glad i changed it out, the former mercon in there looked like used diesel oil when it came out. BURNT! Hopefully it will like its new merconV fill.


which tells you why the tranny failed early, good choice on matching it, though. Better safe than sorry.

 

[Dualie]

there completely separate units. the Tranny failed because it was stressed in day to day use. severe service is an understatement. I have records since new with receipts of Trans flush and fills every 15K.

my Trans issues first started when i bought the truck 10K ago and did a flush and fill with the then recommended merconV. The Trans didn't like it AT ALL. started shuddering BAD ran i even went out of my way to get the mercon V FROM FORD.

Ran that fluid for 3,000 miles and flush and filled with Chevron MD3 but i think the damage was already done.


I have to look through all the records for any proof of servicing the parking brake unit.

 

[Dualie]

Here's a pic of the unit if anyone was having trouble figuring out what it is. It holds a whopping 1/8th of a quart of fluid.

 

[Colt45ws]

My Grandparents old motorhome used one of those behind a C6. Weird idea. We always chocked it as a back up.

 

[Dualie]

I can tell you its exceedingly easy to drive with the parking brake set. makes me wonder how well this thing would do if i actually needed it to work.

Also note that if anything in the drive shaft or rear end fails better hope to all that's holy it does so on completely flat level ground.