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1972 Cadillac Eldorado transmission leak from back cover

Started by Scot Minesinger, April 16, 2015, 09:07:25 AM

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Scot Minesinger

The shop manual states that to replace the timing chain, the engine has to be pulled, when in fact the this can be done without pulling the engine without much difficulty.

For some reason, I'm not great at transmission sealing and so I took this car to have trans sealed by a very reputable shop that has completed several transmission seal work on older Cadillacs for me.  Plus I always see other classic cars there as well.  Anyway they sealed the trans for $370 and I was happy.  Then the next day it was leaking, and after calling the shop they said that if it is leaking from rear cover they have to pull the transmission to seal it and that is $1,000.  I looked under the trans and it is leaking from the rear main cover.  I feel that they should have warned me because they quoted a price of $300 to $600 to seal it.  Plus since it was dropping fluid within 24 hours after it was parked in my garage, they should have diagnosed this leak before I picked up the car.  Their status has been knocked down a few pegs in my mind.

I know boo -who, anyway on to my question, can the transmission be sealed at rear cover without pulling it?  Has anyone done this? 

Thanks,

Scot

Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

"Cadillac Kid" Greg Surfas 15364

Scott,
Look at a shop manual that covers the TH425 and you will see what is under the cover. That cover is the equivalent of a RWD Flywheel/converter cover and is intended to protect the rotating parts, not contain oil.  $1000.00 (if that includes resealing the transmission) is just about right for the amount of work involved.
Greg Surfas
Cadillac Kid-Greg Surfas
Director Modified Chapter CLC
CLC #15364
66 Coupe deVille (now gone to the UK)
72 Eldo Cpe  (now cruising the sands in Quatar)
73 Coupe deVille
75 Coupe deElegance
76 Coupe deVille
79 Coupe de ville with "Paris" (pick up) option and 472 motor
514 inch motor now in '73-

TJ Hopland

The cover he is likely talking about is the 'chain cover'.    The 425 is basically a 400 folded in half.   The torque converter and pump are bolted to the back of the engine as normal.   They basically cut the transmission in half and laid the part with the gears and such next to the engine with the tail pointing forward.  They then used what looks like a really wide timing chain to connect the two sections.   There is a 'tin' cover over this section.    Its got transmission fluid flowing through it to lubricate the chain.   Its not really under pressure but the chain does tend to fling it around so if you have bad seal somewhere you can get a lot of fluid out.   The cover is a thin sheet metal cover similar to the trans and oil pans.   Same as those they can be abused and get bent around the bolt holes. 

I don't know if you can get it off in a 72.   73-78 you can't but they changed the mounts and front frame slightly so maybe there is room?  IF there is there is not much and it would be a crappy job that I would not expect to be successful.   On the 79-85's which are similar I have had pretty decent success just carefully tightening the bolts that I could reach.   On my 73 I had it rebuilt several years ago and apparently they did a good job because its not leaking. 

One thing to check is make sure the pan and that cover are not hitting each other.   They get really close so a little extra gasket or crud in that area can keep things from seating properly.   

Shift shaft often leaks and unlike the 400 its not a lip seal, its just a O ring.  In a 73-78 you can't pull the shaft out while its in the car, it hits the frame before it gets all the way out so you want to be sure to do that if it has to come out. 

Fill tube often leaks.   Its a thicker than normal assortment O ring.  This can be done in the car.

Electrical connector also leaks.   Its a plastic plug with locking tabs and its got an O ring groove in it.  Its a standard O ring.   On mine one of the tabs broke when I was trying to remove it and replace the O ring.   Also noticed there was some fluid leaking around the terminal.  After fighting with it I found out its the same as the 400 and new ones are readily available.   It can be changed by just dropping the pan.   I would for sure replace that if I had the pan off.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Scot Minesinger

TJ Hopland,

Thanks, am familiar with the concept of how they made a TH400 into a 425 by folding in half and adding chain-ingenious, and this may be some valuable advice.  Have printed out your post and will look into trying to tighten the trans chain cover and seeing if it is possible to remove it without removing trans, although as you write it may be unlikely.  Tightening a 40 year old plus light gauge pan with gasket has never stopped a leak before, but it is such an easy thing to attempt, go to try.  If it minimized the problem greatly that might be OK.  Also will be sure two covers do not interfere.  May have to bite the bullet and pay though.  Will keep you posted.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty

TJ Hopland

I figured you had tangled with enough to know what the layout was.   Greg's reply was a bit confusing talking about the flywheel cover.  I'm pretty sure he too knows the layout it just didn't come out right in is post.   I figured most readers have not seen one of these critters so I figured I would explain it so they can better understand what we are talking about.

On mine it looked like they were still factory gaskets and over time the bolts had just got loose and luckily no one before me had tried to tighten or over tighten em.  I was actually laying under the car thinking that there was no way that cover was going to come out in the car and noticed I could actually see a couple of the bolts were loose.   With a 1/4 drive ratchet I was able to get to a little more than half of the bolts.   Before I did that I could actually see bubbles coming from the side of the gasket.   The chain flinging the fluid must froth it up a bit.

Hope it works out for you and your client.    I learned about most of these leaks the hard way.   Even after you have done it and with a lift these are not the easiest to pull.   For sure not the worst but not like say a 60's RWD car with an inline engine and manual trans.   Those were the days when you could pull and engine and trans in about 30 mins.   

StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

bcroe

Quote from: Scot Minesinger on April 16, 2015, 09:07:25 AM
The shop manual states that to replace the timing chain, the engine has to be pulled, when in fact the this can be done without pulling the engine without much difficulty.

For some reason, I'm not great at transmission sealing and so I took this car to have trans sealed by a very reputable shop that has completed several transmission seal work on older Cadillacs for me.  Plus I always see other classic cars there as well.  Anyway they sealed the trans for $370 and I was happy.  Then the next day it was leaking, and after calling the shop they said that if it is leaking from rear cover they have to pull the transmission to seal it and that is $1,000.  I looked under the trans and it is leaking from the rear main cover.  I feel that they should have warned me because they quoted a price of $300 to $600 to seal it.  Plus since it was dropping fluid within 24 hours after it was parked in my garage, they should have diagnosed this leak before I picked up the car.  Their status has been knocked down a few pegs in my mind.

I know boo -who, anyway on to my question, can the transmission be sealed at rear cover without pulling it?  Has anyone done this?    Thanks,  Scot 

There are many things that can be done an easier way, that the manual will not endorse. 
Ask me about changing a 79 Eldo heater core without removing the dash. 

I would first ask if the 72 Eldo trans has ever been worked on?  If not, it is WAY overdue to
be apart for all new "soft" seals inside & out.  Hard parts could be fine, but labor is about
the same as an overhaul (I do my own).  Clutch piston seals at this age are about like a
rock, and if they fail, a clutch pack can loose pressure, burn up slipping, and fill what was
a good trans with awful smelling black poison.  One hangs on my wall. 

The bottom of the chain cover is a problem, and if you see what a narrow bit of case the
cover mates, you would understand why.  What the motorhome people and some like me
have taken to, is using a gasket forming glue to put the cover back.  The factory cork
gasket looks pitiful for this job.  For various other leaks, new O rings may do it.  A little
blue gasket former added on assembly will probably work very well. 

The shifter shaft may leak at this age.  On TH400s there is an outside seal, but rust forms
outside and ruins the seal.  Still working on a fix, maybe braze on some material and turn
it down.  The other form seen on TH425s may have an O ring part way in.  Likely a new
O ring will be enough here.  good luck, Bruce Roe

The Tassie Devil(le)

You definitely have to remove the transmission, or the engine/transmission/diff as a unit.

The Engine/Trans/Diff as a unit is the easiest and fastest way to do it, as there is less to undo.

The Gasket used by the factory is not one of those that can be simply tightened up where it is leaking, but is a hard type, and once tightened, will be disturbed, and leak even more.

It would have been nicer if Cadillac had made the rear cross-member removeable, but alas, not so.   There is no clearance whatsoever to even get the cover back far enough to remove the mounting cover from the back of the motor/trans without raising it up.

When I did it last time, I didn't have access to a replacement gasket, so I sealed it with Loctite 5900.   This stuff is the best sealant I have found for hard to seal fluids.

Bruce. >:D
'72 Eldorado Convertible (LHD)
'70 Ranchero Squire (RHD)
'74 Chris Craft Gull Wing (SH)
'02 VX Series II Holden Commodore SS Sedan
(Past President Modified Chapter)

Past Cars of significance - to me
1935 Ford 3 Window Coupe
1936 Ford 5 Window Coupe
1937 Chevrolet Sports Coupe
1955 Chevrolet Convertible
1959 Ford Fairlane Ranch Wagon
1960 Cadillac CDV
1972 Cadillac Eldorado Coupe

Scot Minesinger

The bolts on back cover were not difficult to get to, so I tightened them all to factory torque spec.  Most were real loose.  I'm not optimistic, but will know in the am.

I agree, even though the trans shifts and operates perfectly, it is likely original, but cannot be sure because it works so well.  Car is of course 43 years old and mileage is past just 80k.  The history is unknown and one of the tasks on my fix it list was to repair the speedometer, which is done, but who knows how long it has been not operational.  The cables (both cruise to trans and cruise to speedo) looked like they got caught in an egg beater and were all messed up.  It looks a lot more like an 80k mile car than a 180k mile car, so I think it is likely under 100k miles. 

After the owner gets it back at some point in a few years the engine/trans will need to come out for resealing trans, resealing (rear main and oil pan) and other maintenance.  If my tightening does not work, the trans removal will be for another day.
Fairfax Station, VA  22039 (Washington DC Sub)
1970 Cadillac DeVille Convertible
1970 Cadillac Sedan DeVille
1970 four door Convertible w/Cadillac Warranty