1980s Trans to Differential cover leak

[Turboba6]

Hi Folks, on 1980 Eldo (350 and Thm 325) I have a Strange Trans Fluid leak mainly from the Final Drive assembly to Trans Bolt shown, I can Actually watch it seep out from there......I 'thought' the Trans was sealed but apparently not, ie the trans AND final Drive assembly (Differential) share the same fluid?

[The Tassie Devil(le)]

G'day Brian,

Unless things have changed, the Transmission and Differential use totally different fluids for lubrication.

If the oil leaking out is really thin and reddish, then it is Transmission Fluid, and if it is thick and black, it is Differential oil.

Bruce.

[Turboba6]

Thanks Bruce, Yes it's Red trans fluid for sure, I'm gonna Drain the Trans, pull that Bolt Dry and Seal it (Locktight) then tighten all those bolts, and RTV the area...Then we'll see..... Thanks👍

[bcroe]

The trans has trans fluid, and the final drive has
differential gear lube.  The final drive is actually
one end of the trans, and contains a shaft seal
between them. 

If the gasket between units leaks, it will be trans
fluid.  Replacing the gasket is not fun, but I did it
a couple times because each of my 79 E cars in time
broke off gear teeth (mfr defect) and had to be
replaced.  I managed to do that in a long evening,
with the steering turned a certain way and the damper
disconnected. 

Those final drive bolts are metric with none too much
thread into the aluminum trans case.  Do not over torque
them and strip the threads, or you will have a serious
problem.  Someone had already done that for me on one
car, I drilled those holes and tapped them as deep as
was possible, and used the longest possible bolt
(each custom fitted) to fix it.  It was good for as
long as I had the car.  good luck, Bruce Roe

[Turboba6]

Yep, easy on the Torque..
Thanks Again Bruce!

[Turboba6]

Just to Update here, those bolts (differential to trans) were Loose, all of them! I removed them, put lock tight on them, snugged them up...No more leak...Easiest fix ever..!!

[The Tassie Devil(le)]

Congratulations on finding the fault, and fixing the problem.

As for using Loctite, I would have just gone the factory way, and tightened them with the correct torque.

But, it would be interesting to fing out why they became loose in the first place.

Bruce R.