Oil Leak from Middle Gear Bearing Cover?

[Geobob]

Developed an oil leak that I am not sure where it is coming from.  This is an 88 with 90k on it and this leak just showed up this summer.  See photos.  I started taking things off and got to the "Middle Gear Bearing Cover" and took the bolts out.  The cover is till glued to the block but as I took out the lower bolts a small stream of motor oil began running out.  So far only about 3 oz have drained.  Clearly this is a gasketed surface so where did this oil come from.  None of the bolts had oil on them.  I just looked at the photos again and it looks clear that the oil came running out the lower center bolt.  I did have the drive shaft and differential off but did not look at the rear drive seal.  I am thinking that is good possibility also.  That is going to require a bit more disassembly to get a look at.  That is where I at for the next few days.  Any thoughts?

Edited November 1, 2020 by Geobob
more detail

[Prairiehammer]

On the middle gear cover, the bolt/cap screw at the six o'clock position should have a copper washer under its head. The copper washer acts as a gasket to prevent oil escaping. If the copper washer has become work hardened (and it is once installed) it will leak when the bolt is reinstalled, even if reinstalled with the washer. The washer can be re-annealed (softened) and reused or it can be replaced with a new washer.
To anneal the old washer, heat it to red hot with a torch and then quench the red hot washer in oil or water. It will now be as new (soft) and capable of acting like the gasket it was.

[Geobob]

5 hours ago, Prairiehammer said:

On the middle gear cover, the bolt/cap screw at the six o'clock position should have a copper washer under its head. The copper washer acts as a gasket to prevent oil escaping. If the copper washer has become work hardened (and it is once installed) it will leak when the bolt is reinstalled, even if reinstalled with the washer. The washer can be re-annealed (softened) and reused or it can be replaced with a new washer.
To anneal the old washer, heat it to red hot with a torch and then quench the red hot washer in oil or water. It will now be as new (soft) and capable of acting like the gasket it was.

well talk about learning something new every day.  I did not notice a leak but after looking at the manual and seeing no other place back there where a seal could be leaking I went back out to the garage and mess is really under that bolt and not so much the rear end of the "Middle Gear" where it exits the back of the motor.  Could it really be this simple.

I try the anneal process.  Sounds simple enough and worth a try.  At least if I clean up the area I can then watch for evidence of the new leak

Edited November 3, 2020 by Geobob

[Flyinfool]

A replacement copper washer is also pretty cheap.

That bottom hole is the drain plug for the transmission. Oil is supposed to come out if you remove it. For normal oil changes the transmission does not trap enough oil to matter so it is not worth the effort to pull that plug. the only time you would want to make the effort of draining the trans if if you are dealing with a contaminated oil issue like gas or coolant in the oil where you want to drain every drop possible.

Anneal or get a new washer and slap it back together and your good to go.