727 leak @ tailshaft when on jack stands?

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67dartgtgo

67dartgtgo

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Guys,
I have a 360/300 magnum crate backed by a year old rebuilt 727. Funny thing is it leaks tranny fluid out the tailshaft housing @ the driveshaft when the front end is on jackstands for a signifigant length of time. I first noticed it when I left it up overnight for brake work and found a puddle under the tranny. I'd love it if you guys could make me smart on this. :coffee2:
 
Trans fluid will pour out if the driveshaft isn't installed, but if it's happening with the driveshaft in, you've got a bad seal, bigtime wear on the sealing surface of the yoke or both.
 
Driveshaft in....and only leaks when the front ends up...yoke is smooth and even. Suspecting bad seal and asume it's an easy replacement with removal of the driveshaft?
 
67dartgtgo said:
Driveshaft in....and only leaks when the front ends up...yoke is smooth and even. Suspecting bad seal and asume it's an easy replacement with removal of the driveshaft?
Click to expand...

Not too bad really. Pry the old one out and tap the new one in. It's nice to have a piece of PVC that fits around the seal to use as a driver. As long as it's not corroded in, it shouldn't take more than about an hour or so.

Jack the *** end up so you don't get a ATF shower.
 
Another area to check is at the plug inside the slip yoke (see picture below, yellow arrow is pointing to the plug). I've had this happen and it can appear as a leaking seal. You would need to really clean off all the old tranny fluid (ensure it is dry) and raise the front of the vehicle and recheck for the source of the leak.
 

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Thanks ram.

Demon, Will do. How would you repair a leak like that on the yoke? Seal weld it maybe or did you have to get a new one?
 
67dartgtgo said:
Thanks ram.

Demon, Will do. How would you repair a leak like that on the yoke? Seal weld it maybe or did you have to get a new one?
Click to expand...

Mine was well used so I just bought a new slip yoke. But I'm sure if you took it off the driveshaft and cleaned then sealed it would work.
 
Demon 408 said:
Another area to check is at the plug inside the slip yoke (see picture below, yellow arrow is pointing to the plug). I've had this happen and it can appear as a leaking seal. You would need to really clean off all the old tranny fluid (ensure it is dry) and raise the front of the vehicle and recheck for the source of the leak.
Click to expand...

x2 - beat me to it...
 
All good things to check. Will add that hopefully the extension housing bushing was changed when rebuilt. If it wasnt a new seal wont do any good.
 
simple seal issue was the obvious guess here too. '408' is right on about the slipyoke. easier to check it with air compressor though. and the last one about the tailshaft bushing...my old valiant had the driveline get hit hard and made it out of round. it tore up that bushing in the trans terribly. it leaked, i replace the rear seal, it leaked in a couple days. that bushing has thin sharp metal and turned out the pieces of the wasted bushing were eating the new seal.
 
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