1984 Eldorado TH425 leaking

[danjarrett1]

I will in western KY, my transmission needs to be resealed. Does anyone have a resource that understands these TH425's that might be able to reseal mine? I would say anyone within 500 radius of me would be good, thanks

[bcroe]

The 84 was built with the 4 speed version of
the TH325, a much lighter duty unit than a
TH425. However the biggest leak problem may
be the same, the big chain cover on the back. 

Many have removed the cover and the original
cork gasket, and used an appropriate glue to
put the cover back on.  This similar to valve
covers of the era.  Has worked for me.  I
doubt this job can be done without removing
the trans.  good luck, Bruce Roe

[danjarrett1]

Thanks for that! I believe you re correct about where it's leaking

[TJ Hopland]

I was just looking at an engine and transmission combo I have in the garage and I'm pretty sure 85 had the single rear mount so there is a fairly large bracket that attaches above the rear cover that covers a decent chunk of the rear cover that then holds the mount.  That would have to come off to get the cover off.  I don't remember it being super tight but if there is room it would have to be darn close.  Would also be fun to try and clean the surfaces while its in the car. 

May be worth checking the bolts that are easy to access.  Don't go nuts but maybe there are some loose ones that will slow the leak down a bit?

[danjarrett1]

My bad....my Eldo is a 74.....but you're likely right, same problems in the TH325

[The Tassie Devil(le)]

With these FWD Eldroados, the Transmission has to come out to get the cover off.  If you cannot get the correct replacement gasket, I recommend using Loctite 5900 as a sealant.  It is compatible with oils, including Transmission Fluid.

Just make sure the tin surface is straight, as simply trying to tighten up the bolts to stop the leak, will make it worse, and bend the flange, compressing what is left of the cork gasket.

I cut a long 1/4" bolt as a guide for reinstalling the cover.   Makes life easier.

Bruce.

PS.  I found it easier to take the Engine and Transmission out as a unit, complete with the third member.

PPE.   Attached is a picture of the cover.   Note how narrow the bottom is.

[TJ Hopland]

Have you got a chance to get under it and look close and see what area(s) are wet?  Where the dipstick tube goes in is a common place for leaks on these especially if it has to sit a while before it starts leaking.  Shift shaft is another place that often leaks.

[smokuspollutus]

The chain cover was shored up somewhat by 1985...still a very old seal at this point though.

A common spot is the selector shaft seal. Need to do some surgery to change it in a front wheel drive car unlike the rear wheel units. Still easier than the chain cover!

Does the car engage in gear immediately after a cold start from sitting for days/weeks? Converter drainback will flood the lower pan and selector shaft/dipstick tube area to the point that even a "good" seal will leak.

[TJ Hopland]

Ya I think on the first gen they didn't trust the chain so they doubled the width to be safe but by the 2nd gen not to mention the engines making half the power they went to a much narrower chain.

74 would also again have the issue with the rear mount bracket taking up any space there is back there. 

[danjarrett1]

Dipstick port is not leaking, the nut for the Speedo cable was loose and had some leakage, but tightened that up, seemed to solve that issue I think the chain pan gasket is leaking.

[TJ Hopland]

About all you can do with that then is snug up any bolts you can reach.  Don't go nuts and bend the cover but maybe if there are loose ones you can slow it down a bit.

[danjarrett1]

That's my plan, I did tighten those up on the bottom that I could reach, will go to the top side and do the same