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C4 Open Discussion General and technical C4 Corvette discussion - ownership, maintenance, repairs, modifications, tuning |
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05-04-2013, 10:49pm | #1 | ||||||
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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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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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05-05-2013, 9:06am | #3 | ||||||
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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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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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05-05-2013, 11:57am | #6 | ||||||
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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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05-05-2013, 1:05pm | #7 | ||||||
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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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05-05-2013, 9:22pm | #9 | ||||||
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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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05-11-2013, 3:14pm | #11 | ||||||
A Real Barner
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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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05-11-2013, 3:19pm | #12 | |||||||
A Real Barner
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Additionally...
From Bill (ZFDoc) Boudreau; Quote:
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05-11-2013, 3:33pm | #13 | ||||||
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05-11-2013, 4:42pm | #14 | ||||||
Barn Stall Owner #46
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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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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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