Good afternoon FTE. The 1992 F-Super has a severe oil leak from the parking brake. This parking brake is not the original one, it's from a different application, and it has a hole with a speed sensor in it. The oil is leaking out of the sensor hole and I need to do something about it so the parking brake doesn't burn up and leave the truck dead in the water during a really busy time. It's bad enough that it's been filled completely with No. 2 grease, and even then it needs to be refilled every 1,000 miles or so.

Got to thinking, eventually I should probably fabricate a plug to fill the hole, since the sensor is delicate and expensive and completely unnecessary on my application. I may do that come slow season. In the meantime, I'm being lazy about it and/or don't want to be fussing around in my mud driveway to fix this- does anyone know of an off-the-shelf plug or block-off plate for the speedometer cable holes that were used on various driveline components on our trucks? It's the same VSS-over-speedo-gear setup used in the 1356 transfer cases on many of our trucks, like this (link).

TIA for any info y'all can share, all the best until next time!

 

hhow about a picture of your driveshaft brake youre speaking of (right?) and the size and location of the opening

 

That is a regular speedo cable hole, just put a cut off cable end from the junkyard in there
Or a used speed sensor for cruise control
They do make plugs for the ones in between ABS speed sensors on the rear axle and the E4ODs that have no provision for a speedo
Supposed to be filled with GL-5 gear oil, your grease will work

 

that would be my way of doing it.......or stuffing a cork in the hole. depends on what is available.

 

Thanks for the replies, lady and gentlemen, sorry I've been away for a few days. Looks like for now I'll just buy a new sensor, and come summertime I'll fabricate my own plug for it. BTW, I am 100% certain it is not supposed to have gear oil in it, the manual and the tag on the case for the old one both specify Mercon 1. However, for a long time, I have been filling it with gear oil anyway, since it only has to leak about 2 fluid ounces before it's completely dry and fries the bearings. Maybe the sensor body doesn't like gear oil and that's why it leaks now, who knows.

 

The ones online I saw said GL-5 on the tag
If yours said Mercon then Mercon it was / is
I agree, you can probably get away with just about anything in there
Mercon sounds a bit lightweight to me, but there are only bearings in there that need the lube
All the aluminum cases took Mercon anyway
Does yours have an aluminum case?

 

What do you mean sensor body?
Post a picture if you can
The old plastic speed sensors would leak around the o ring inside them
They would also send oil up the cable housing if the sensor leaked internally
Besides the speedo cable housing or cruise VSS
You should not have anything in there to leak besides the rear output seal and the front input seal

 

I'm not going to get a picture anytime soon, the driveway is 100% mud this week and the truck won't be elsewhere for the next few days. In the sensor I posted a link to, oil comes between the body of the sensor- the blue aluminum piece- and the black -plastic piece. I've seen it happen countless times on these sensors, it's not unusual at all which is why I figured the aftermarket may have addressed the issue. The 1356 transfer case in my half ton does it all the time, as did the last 2 I owned.

You are correct that usually there is no sensor to leak- just two seals and a vent. This particular parking brake is from something else- I think a 2000's E-450, but I'm not sure, the junkyard didn't write down what it's from- but apparently it was something that needed a speed signal from the output shaft.

This is the first I've ever even heard of one of these brakes calling for GL-5 or having an iron case- do you by chance have a link to that?

 

Does it look like this?

https://www.thedieselstop.com/member...atest-activity

https://www.thedieselstop.com/member...atest-activity
I did a little bit of googling, im entirely out of my domain on this but I did find this website and based on the technical details provided by that User, I trust that hes at least knowledgeable if not he was an actual engineer working on these systems. If you have an account there or care to make one, or find him on another forum, you probably can get some assistance in IDing it better.

Also, how do you know the unit calls for GL5? The only situation I can see it calling for GL5 is if your transmission calls for GL5 like how many t-case/transmission combos will call for the same fluid.

Later GM sm465s will call for ATF instead of gear lube partially for shifting performance in the cold, but also because if the transmission leaks, instead of GL4 (yes, GL4. Not GL5 that claims to work with GL4.) gear lube mixing with ATF in the NP208 transfer case, you have ATF mixing with ATF. The same type presumably. Although my example isnt the best since the leak would have to fill quite a bit of the space in the adapter before it would even be near the seal for the NP208. But an auto 4x4 700r4 to NP208 is a better example since they mate much closer.
I use this to ask because what type of fluid do you use in your ZF transmission? Is it possible you use GL5 and you were told to put GL5 in it because of that fact?

If its leaking from the body halves it sounds like you need a new sensor, but those are pricy. you dont have a cable in it right? Ive found forums people said they use a speedo cable, insert it into the sensor , cut off most of the cable so it has a short bit exposed, then shrink tube/RTV/JB weld the end so fluid cant escape the tip of the now cut cable, then call it good. however, i find it interesting a 2000s anything would have a Speedometer cable . the Speed sensor makes sense, but most things in the 2000s you would expect to use that signal and not a cable for anything I can think of. Are you sure the right sensor was even installed? I would just fabricate something at this point if the surface isnt too complicated, you should have a hold down bolt to use to help clamp whatever you make down.

edit: I just saw that manic is the one who said gl5 not you originally. Well, if you have 2wd and are using a 2000s brake unit, its probably meant to take Mercon V. What fluid do you use in your ZF?

 

You will see a few of them for sale on Ebay
In the pictures, their tags say GL-5
They all had cast iron cases before about 1980 when the aluminum transfer cases came out
It was common for those old VSS's to leak oil, just replace it
If you look for new ones, they are all aluminum cases, the older rebuilt ones I saw had cast iron cases