Chasing a transmission fluid leak

[77silverbullet]

Recently acquired a '77 C20, I believe it has the TH350 tranny.  I've driven just a few time, its spent most of its time in the driveway, which has a typical slant from the garage to the gutter.  After a few weeks it sitting, I noticed that it started leaking red ATF onto the driveway.  Some quick searching and I was sure it was coming from the pan as that seems to be the most common source.  Bought a new pan gasket and filter and waiting for the weather to warm up a bit so I can tackle the fix.

However, when I went to move the truck into the garage to start the repair, a closer look revealed that the dripping was coming from what I now know is the yoke.  Some additional searching and I thought I had it figured out.  I found a page that seemed to accurately describe what I was seeing, and it indicated that the fluid was coming from a weep hole in the yoke (here is the link to that page: http://www.73-87.com/7387garage/drivetrain/yokeleak.htm).  I definitely saw the drip coming from the bottom portion of the u-joint.  There was not evidence that the fluid was coming from the extension housing seal, no trail of fluid running down to the yoke/u-joint area.

So with my new plan, I pulled off the driveshaft (it has the 2-piece) and removed the extension housing only to discover that my setup does not have the cup and o-ring described on that page.

With all of that, here are my questions:

Should there be some ATF in the extension housing?  Seeing both the gasket on the extension housing where it bolts on as well as the seal where the yoke slides in makes it seam like some fluid is expected.  If thats true, what is supposed to keep that fluid from making to the weep hole of the yoke and then to my driveway?  Is possible that someone prior to me removed the cup and o-ring?  Or is that only on the 700R4 from the other page I referred to previously?

Appreciate any help that can be offered, I'm very new at any tranny work.

[VileZambonie]

You should have an oring seal. You can always just squirt some rtv in the weep hole


Sent from my iPad using Tapatalk

[77silverbullet]

Thanks for the quick reply.  I thought the same thing, that it should have an o-ring seal.  So, I went to the junk yard this morning and found one similar to mine and took the drive shaft and tail housing off.  It looked almost exactly like mine (except that it was a few years newer), and also did not have the cup and o-ring.  Makes me think mine never had it.

As far as sealing the weep hole with RTV, any risk in that?  I can't but think it was put there for a reason.

[bake74]

     Does your output shaft look like it might have had the cup on it at 1 time ?  I am under the impression either you are missing the cup and o-ring or someone put the wrong transmission yolk in.  Maybe yours was never suppose to have the yolk with the weep hole.

[thefarmboy21]

It would help with pics....usually besides the pan gasket, the two most common leak areas are the dipstick tube grommet and the rear seal where the yoke slides in. There are also a couple holes on the tail shaft where the speedo cable and maybe another bolt in.