I've got an '88 F450 with a ZF 5S-42 tranny... the version with the parking brake assembly mounted on the tail end. I've owned the truck since late '99 and have had a recurring problem with the parking brake assembly apparently leaking its fluid and the bearings subsequently frying and seizing the drive line, along with melting the plastic speedometer drive gear. I frequently check the fluid level since the first occurrence, but this is apparently not enough. :-(

The parking brake assembly has its own lubricant reservoir, and apparently something is causing the seals to wear/fail prematurely, thus causing the above mentioned problem. Has anyone had similar problems? Or, can anyone shed light on what may be causing this recurring dilemma? I'd like to find out if this is a common problem with these parking brake assemblies or if mine is a special case.

Many thanks,
Bryan

 

so its on the tail shaft of the tranny?? I would check your carrier bearing and your U joints to make sure your drive shaft aint moving around and ovaling out these seals...

 

Thanks for your reply stkdram55.

I called a shop that specializes in these trannies and found out that the brake assemblies are balanced, meaning if they are disassembled after balancing, then reassembled in a different orientation, you can end up with vibration that will wear out the seal.

I dropped the parking brake assembly on my rig and found a welcome relief... the speedo cable was broken and the parking brake is fine... my initial assessment was (fortunately) all wet.