What goes here?

Woodsplinter · Jul 17, 2014

I removed the propeller shaft between the transfer case and the front rear differential so I could remove the parking brake shoes. On the end of the tube facing the parking brake drum is a hole.

The TM states that there is supposed to be a "breather" there. Does anyone know what this is and where I can get one. The breather cap that is used on top of the axles would be too tall. The edge of the hole is ragged and I can't tell if it was ever threaded but the TM indicates it was.

Grease has apparently been leaking out of the hole for some time as there is plenty around the parking brake drum shield.

The breather is listed as item 2 in the TM.

Thanks!

View attachment Deuce Propeller Shaft.pdf

phil2968 · Jul 17, 2014

We use these at work all the time.
http://www.saeproducts.com/grease-fittings-H200317400.html

Jeepsinker · Jul 17, 2014

That hole allows excess grease to exit the slip joint when it compresses. I've never seen one capped with anything and I wouldn't put anything in there.

Woodsplinter · Jul 17, 2014

Jeepsinker said:
That hole allows excess grease to exit the slip joint when it compresses. I've never seen one capped with anything and I wouldn't put anything in there.

The more I look into this, the more inclined I am to agree with you. But I am curious why the TM indicates there is a breather or relief valve there.

Flyingvan911 · Jul 17, 2014

It may just be referring to the hole itself. The hole will relieve quite a bit of excess grease.

Floridianson · Jul 17, 2014

I don't know but it looks like something was screwed in there at one time. I will look at one of mine tomorrow.

Woodsplinter · Jul 18, 2014

Flyingvan911 said:
It may just be referring to the hole itself. The hole will relieve quite a bit of excess grease.

On the TM it shows a drawing of the "breather" and instructs you to remove it when taking things apart and to replace it upon reassembly. I can't find a part number for it though.

After disassembling the shaft, I can see from the hole where the grease zerk is installed, out through the hole in the end of the tube. It appears that grease pumped in here could just be pushed out the hole when the shaft compresses.

rustystud · Jul 18, 2014

Most modern trucks and busses just use a metered orifice (small hole) relief valve now. If you do not allow the grease to escape you will have a hydrolock in your driveline ! Things tend to get bent when this happens ! Usually the metal cap ( looks like a freeze plug) just blows out.

rustystud · Jul 18, 2014

phil2968 said:
We use these at work all the time.
http://www.saeproducts.com/grease-fittings-H200317400.html

Yeah, those are the relief valves I was talking about.

phil2968 · Jul 18, 2014

I can send you one.

Woodsplinter · Jul 18, 2014

rustystud said:
Most modern trucks and busses just use a metered orifice (small hole) relief valve now. If you do not allow the grease to escape you will have a hydrolock in your driveline ! Things tend to get bent when this happens ! Usually the metal cap ( looks like a freeze plug) just blows out.

Ok, I see what you mean. So would you leave the hole open or install the metering valve?

Woodsplinter · Jul 18, 2014

phil2968 said:
I can send you one.

Does that valve allow grease to escape or just air? Do you think an auto parts store would carry them?
If it doesn't allow grease to escape, I agree with Rusty that it would be bad to install.

Floridianson · Jul 18, 2014

Phil do you have him covered as I grabed one this morning off an extra shaft.

DieselBob · Jul 18, 2014

phil2968 said:
We use these at work all the time.
http://www.saeproducts.com/grease-fittings-H200317400.html

Well they say if you learn just one new thing than the day wasn't a waste. I have worked on everything from lawn mowers to Cat D9 bulldozers over the last 40+ years and have never run across one of those relief valve assemblies. Interesting.

Woodsplinter · Jul 18, 2014

DieselBob said:
Well they say if you learn just one new thing than the day wasn't a waste. I have worked on everything from lawn mowers to Cat D9 bulldozers over the last 40+ years and have never run across one of those relief valve assemblies. Interesting.

Yes Bob, I agree it certainly is interesting- I have quite a knack for stumbling onto "interesting" things. Unfortunately I usually end up scratching my head and wandering off not having a clue what I just found.

Floridianson · Jul 19, 2014

Let me know if Phil has you covered. The one I grabed has a ball and spring and two little relief holes in the sides of the hex head. Then it has a what looks like a very small pop out plug in the center of the hex head. Yea I can see now if something like that was not there and you pumped in too much grease seems like you could blow off the seal retaining cap and seal messing up the threads for shure. I would think any drive line shop would have them if you can't wait.

rustystud · Jul 19, 2014

Woodsplinter said:
Does that valve allow grease to escape or just air? Do you think an auto parts store would carry them?
If it doesn't allow grease to escape, I agree with Rusty that it would be bad to install.

I didn't say it would be bad, I said you need a relief valve to prevent damage. If the grease has no where to go, (as when the driveline is moving in and out) it will act just like a hydro-locked engine and bend or break parts ! I would use the new relief plug as this will prevent crap from entering the slip yoke. If you have too, just tap a new thread into the end. The relief valve allows excess grease a way out.

phil2968 · Jul 19, 2014

I have not heard from him James. I have one if he wants it or maybe he would like an OEM one like yours.

Woodsplinter · Jul 19, 2014

rustystud said:
I didn't say it would be bad, I said you need a relief valve to prevent damage. If the grease has no where to go, (as when the driveline is moving in and out) it will act just like a hydro-locked engine and bend or break parts ! I would use the new relief plug as this will prevent crap from entering the slip yoke. If you have too, just tap a new thread into the end. The relief valve allows excess grease a way out.

Ok, thanks for the clarification. I just sent a PM to Phil.

nchittendon · Jul 19, 2014

Interesting. So it's something similar to the "breather" found on the axles? The little spring loaded cap that farts air out.....

I can't imagine it would last long due to grease catching everything and just hanging onto it. Wouldn't take long to clog up IMHO.

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