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Old 05-04-2013, 10:49pm   #1
mike100
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Default Warning: Actual C4 tech question.

So I dropped my exhaust to install headers (yay). While it is off, I want to investigate my ZF tailshaft leak. Ok, so I'm thinking the rear seal is bad, but I sprayed it down with brake cleaner twice and it still leaks. I haven't started the engine in like a month now (I know, I'm lagging on this project).

The seal is dry as can be, but the oil keeps coming from the yoke center- like along its axis. Is that even possible? Is there a hairline crack or something?






maybe its running from the top, but mmm, for a month now? I clean it up and 3 days later the drops hit the garage floor/

So looking at the pic, the oil seems to come from the flat surface 3/8 inch from the u-joint. I want to call Bill B (the ZF Doc) to confirm, but this would be the first time in my life I ever saw bad d/s yoke metallurgy.

Last edited by mike100; 05-04-2013 at 11:03pm.
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Old 05-05-2013, 12:46am   #2
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Don't feel bad, I still wonder where half of one quart went with no leaks at all.

Drive the Z until it reaches Op Temp and look at it again.
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Old 05-05-2013, 9:06am   #3
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Quote:
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Don't feel bad, I still wonder where half of one quart went with no leaks at all.

Drive the Z until it reaches Op Temp and look at it again.
It has been leaking for a year. The pipes burn it off. I hope it needs a new yoke.
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Old 05-05-2013, 11:04am   #4
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I assume the seal is new....back when you fixed the 2nd gear.
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Old 05-05-2013, 11:50am   #5
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May be some porosity in the metal. Seen it before....unfortunately, the only way I know of to really test this is to replace the yoke and see what happens.
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Old 05-05-2013, 11:57am   #6
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Quote:
Originally Posted by PLRX View Post
Don't feel bad, I still wonder where half of one quart went with no leaks at all.

Drive the Z until it reaches Op Temp and look at it again.
It is and the yoke bushing in the tailshaft is new also. I was pretty sure the seal was bad or there was too much play- but surprisingly, this is what I found.
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Old 05-05-2013, 1:05pm   #7
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May be some porosity in the metal. Seen it before....unfortunately, the only way I know of to really test this is to replace the yoke and see what happens.
Can a machine shop polish it?
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Old 05-05-2013, 4:05pm   #8
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Possibly.

My first real experience with metal porosity was on the wheel on my 84. Was losing about 5 psi per week. Turned out the metal was porous. I had the tire dismounted and applied a thin coating of JB Weld over the spot. Problem was solved. Probably not possible with a drive shaft yoke though.
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Old 05-05-2013, 9:22pm   #9
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Quote:
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Can a machine shop polish it?
I would think a machine shop could check it for cracks too. It's pretty simple to do.
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Old 05-05-2013, 10:00pm   #10
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Metal porosity can be a real bitch. Once when I was racing I had a block bored .030 over. Everything checked out good so I put it together, started it, set the timing and let it warm completely up. I then shut it down to pull the valve covers & reset the valves. Got that done put the covers back on & went to start it again, it was locked up! I ended up tearing the heads off again to see what went wrong and I could not find a thing. Cleaned out all the cylinders so they were dry and went to check gaskets, came back & #3 cylinder had water in it! I wiped it out again then stood with a light right over the bore. All of a sudden a drop of water started forming on the cylinder wall. That engine was a running engine but when they bored it the hit a spot where there was just no material. The hole could not be seen either.
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Old 05-11-2013, 3:14pm   #11
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UPDATE with Pics:

took it apart and could clearly see the freeze plug-like spline end cap is leaking. Not too common, but a quick search on the internet does bring up the phenomenon.


I could have probably got away with JB-Weld-
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Old 05-11-2013, 3:19pm   #12
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Additionally...

From Bill (ZFDoc) Boudreau;

Quote:
Just to warn you up front, finding a suitable slip yolk replacement will be extremely difficult since SPICER discontinued production of the 2-3-13131X slip yolk assembly. There is no shortage of replacement slip yolk assemblies that claim to be exact replacement units of the original SPICER unit, but what they don’t tell you is that in new form, these knock-offs have the same excessive spline play equivalent to an original 2-3-13131X slip yolk with 100K miles spline stretch on it.
I did find one genuine replacement yoke in Florida- $195. Decided to fix my 37k mile one.
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Old 05-11-2013, 3:33pm   #13
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Quote:
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$195
Damn Mike, that a lot of ca$h, you could have use JB weld, regular welding or anything else. Test it for a day or two, then make a decision.

One thing is you found out what it is and will get it fix soon.
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Old 05-11-2013, 4:42pm   #14
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Your simple weld should work fine. No way I'd fork over that kind of cash if it's a simple fix.
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Old 05-11-2013, 7:51pm   #15
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Looks like a solid fix. I'm willing to bet your leak will be fixes for ever.
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