1970s 1979 Eldorado Transmission leak

[Turboba6]

Hi Folks,

  On my 79 I have done the Pan Gasket Twice, second time with Cork and RTV Black, thinking that was my leak
as it seems to run down there, dripping onto the exhaust on the Drivers side, dipstick tube is there Looks dry but its hard to tell...Thoughts?

[The Tassie Devil(le)]

One thing that concerns me is that RTV is incompatible with Automatic Transmission Fluid.

I have found that the best is Loctite 5900.

When you did the trans pan gasket, did you ensure that the pan sealing flange was flat?

How does the Transmission Chain Drive cover look?

Bruce.

[Chopper1942]

The fill tube seal and shift shaft seals are areas the frequently leak. Best bet is to get some dye for an automatic transmission and pou it in the fil tube.  Take it for a drive. Raise the vehicle and put on jack stands. Use a black light to find you leak source. the dye leaves a yellow trace. When you find the leak, drain and save the fluid. Do the repair, wash off the dye traces with brake clean, use a strainer and pour the drained fluid back in the trans, road test, and verify the repair with the black light again.

Using the dye will keep you from guessing the source of the leak.

[SaltLife97]

If the 1979 Eldorado is like my 1973, MY leak came from a small ORing on the transmission selector lever shaft that comes directly out the side of the transmission. It would seep from there and drop along the side making me think it was the gasket. The way my car is, I can only partially remove the shaft partially as it will hit the frame without raising the transmission. I had to cut the old Oring which was shrunken, and cut on the new one. I superglued the cut ends together and it hasn't leaked since.

[bcroe]

Unlike my older 400/425 transmissions, I found the
shift shaft on the 79 TH325 is quite difficult to
get out for service.  Bruce Roe

[Turboba6]

Ok, well to Update here, it is the Drive Chain Cover on the Back of the trans (325 of course) that is leaking!!
Some of the bolts that are visible are loose, I'm assuming this cover can Not be removed in place?  Perhaps tighting the bolts (I can Reach) and Covering the Seam with Gasket sealer would at lease Greatly slow it down??

Thanks!

[Turboba6]

Anyone??

[bcroe]

Try tightening the bolts and see if it helps. 
After that pull the trans (probably with the
engine) and see about gluing the cover on. 
That is what happened here, on a conversion
from TH325 to TH425, which probably would
leak more.  good luck, Bruce Roe

[The Tassie Devil(le)]

When I had the chain cover gasket leaking, I glued the cover on with Loctite 5900.   Worked a treat.

BUT, the Trans has to come out to gain access, as everything needs proper cleaning.

Bruce.

[Turboba6]

Thanks Bruce, yea Pulling them both together is the smart move...!

[The Tassie Devil(le)]

It is easier to pull them out as a unit, as trying to separate the engine from the trans in situ is a real pain, as well as getting them back together afterwards.

I have had them out of my '72, and there are a couple of secrets that aren't in the shop manual that make the task easier.

I know I wrote up a thing on it many years ago, and will have a try looking for it.

Bruce.

[TJ Hopland]

The 79-85's are a little lighter and smaller than the 71-78's were so its really not that bad of a job to get them out.   You don't even have to remove the hood, just disconnect the struts and it will hinge back.  Wish that was the case with the 71-78 where the hood itself weighed a ton.