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1946 Trans slipping

Started by Perry McComb, November 16, 2018, 11:35:52 PM

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Perry McComb

Hello,
I changed the fluid in my hydra-matic and it started slipping it was working fine before I changed it
First I put a hose down the dipstick and pumped out what I could then added new fluid that is when it started slipping so I drained all of it including the torus cover put in 12 quarts of new fluid it still is slipping. The trans only has about 200 miles on the rebuild 10 years ago

Like I said it was just fine before I changed the fluid could I have knocked something loose when I put the plastic hose down the  dipstick
hole any advice would be appreciated
Perry

savemy67

Hello Perry,

I have a '48 Hydra-Matic dis-assembled in my garage.  As far as I can determine, I think it is unlikely that you knocked anything loose by inserting the hose in the filler tube.  The valve body, and band adjusting screws are on the other side of the case.  And the fluid pick-up screen is held in place by both front and rear pump pick-up tubes.

Do you know what type of transmission fluid was used when the transmission was rebuilt 10 years ago?  Why did you change the fluid if there is only 200 miles on the transmission and the car was operating OK?  What type of fluid did you use?

I think the '46 Hydra-Matic has a drainplug at the rear of the pan.  Do you not have a lift or other means of safely getting under the car to drain the transmission pan?

If nothing mechanical was disturbed by the insertion of the hose to pump out the old fluid, then either the fluid is incompatible, the fluid level is not correct, or coincidentally something failed that is causing the transmission to slip.  Do you have the shop manual for your car?  And were you scrupulous about following the drain/refill procedure?

I would hate to see you have to remove the transmission to fix the problem, but that is a possibility.  Can you provide any more information?

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

"Cadillac Kid" Greg Surfas 15364

Perry,
It is possible you knocked the oil pick up screen off the pump inlet tube. The most logical thing at this point would be to drop the transmission pan and see if everything is in place.
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-

Perry McComb


Perry McComb

So I took the pan off and the screen was ok. It looks to me like the front bands are loose I'm not sure if they are supposed to be that way or not. Can anyone help me with that as far as the bands ? If they are loose do I need a special tool to adjust them ?
Thank you
Perry

savemy67

Hello Perry,

There are special tools for adjusting early Hydra-Matic bands.  There are internal adjustments, done with the pan removed, and external adjustments, done from inside the car.

The internal adjustment for the rear band uses a tool that can be purchased from Dave Edwards at AutoTran.us.  I don't know if he has the front band adjusting tool, but you can fabricate one easily as was done here:

https://www.youtube.com/watch?v=onBkjvwGgEs

Or you can search for the tools online.

The external adjusting tool sometimes shows up online as well.  It would be a little more difficult to fabricate than the internal front band tool, but not impossible.

More importantly, the external band adjustment is done with the car running. The rear wheels (or entire car) need to elevated, and you need a tachometer to measure engine RPMs.  Do you have a shop manual?

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Bobby B

Yes...Bands appear loose when there's no pressure on them. I have the internal and external servo adjustment tools for your bands. If you have the pan down, it's way more accurate than the external tool. You shouldn't need adjustment if the trans was just redone. Did they use all new parts or just replace wear items? I would make a phone call to the shop that did it first, and go from there. You're more than welcome to borrow what you need. I have all the tools, books, etc., for the Hydra-Matic.
Good Luck....
                   Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

jackworstell

Just a note....if you do the internal method I don't see any reason to do the external method...
both methods do the same thing...……...with the internal method reportedly being the more accurate.


Of course using the external method doesn't require dropping the oil pan

Jack Worstell        jlwmaster@aol.com

jackworstell

In which gear(s)   is it slipping ?   Knowing this would help pin down the problem.

For example...if it slipping in first gear then more than likely either the front band or the rear band
is not being applied tightly by the servo(s).     Of course then would lead to the next question...why not
being applied properly ?   Low oil pressure due to worn front oil pump ?   ( the rear pump doesn't due anything
until the vehicle is in motion)  Or low due to
a faulty internal seal somewhere ? Or due to something sticking in the control valve assembly ? Or ?

If goes OK in first gear but slips in second then most likely the rear clutch pack is slipping or the front band is slipping

And so on.

The above greatly simplies this trouble- shooting procedure but you get the idea  The best thing is to get
a Hydramatic manual  which includes the entire trouble-shooting scheme ...as I recall there is a 1946 Cadillac manual which does this.

Here's where you might start.
    Double check the fluid level
    Adjust the bands internal method if possible or if not the external method
         The bands can be adjusted without the special tools but this is crude and
          I don't recommend it unless you have no other chioce
     Check oil pressure.  There is a plug on the case you remove to hook up a gauge
           with a long tubing extension so you can get the gauge out where you can read it.
            As I recall the gauge should read about 80#  ??

I take it you removed the plug that drains the fluid coupling and drained the coupling along with
the rest of the transmission.   Once empty the coupling has to be refilled via going
thru an internal check valve ( which is pushed open by oil pressure )   If for whatever reason the coupling did not refill completely....the transmission will not move the car.   But if you put back in 12 quarts...it seems to me that this is not the answer

Long shot ( very )...when you drained the transmission maybe enough fluid drained oil out of the front oil pump
to the extent it lost prime  ???   I had this to happen to me once just after I had rebuilt a 727 Plymouth
transmission.   But not quite the same.  After I put the 727 back in the car it wouldn't move the car
I dropped the oil pan.... removed the filter and improvised a way to force oil into the pump via
the oil intake tube.  I got lucky and it worked.   But here I had cleaned  the oil and forgot
to pack it with thin grease before I re-installed it.   in your case you didn't remove the pump and clean
it out......you just drained the transmission......so there should have been enough oil left in the
pump to prime it upon the next start-up
I mention this long shot (very) only because it is one of very few things that might explain
why a transmission would slip after the only that was done was a simple oil change

I           

jackworstell

#9
To    savemy67

You said you have a  48 Hydramatic taken apart....would you check the intake tubes for the oil pumps
( especially the front pump ).    Would it be possible to loosen these intakes
such that appreciable air could be sucked in ?
Of course if much air is sucked in the pump(s) will...not.... deliver enough pressure

Frankly as I recall the intake tubes are pressed into the pump bodies and would
be difficult to loosen...….

Jack Worstell        jlwmaster@aol.com

savemy67

Hello Jack,

I am posting here in case others want to know, and I am emailing you at the email in your post.

On my '48 Hydra-Matic, the pick-up tube for the front pump is bolted to the pump (photo 5074).  The bolts include a locking mechanism so that the bolts cannot loosen nor the tube fall out.

The pick-up tube for the rear pump (photo 5075) is a press fit, but very secure.  When the tubes and the screen are installed, they are sort of "locked" in place by virtue of their restricted movement once assembled.  I think it would be almost impossible for the tubes to loosen enough to cause cavitation in the pumps.

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

"Cadillac Kid" Greg Surfas 15364

Chris
The filter just slides on/off the pick-up tube
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-

jackworstell

Thanks for the info Chris.       Refreshes my memory.
     The chances of air being sucking in via a loose intake tube looks to be very remote.


Jack Worstell

savemy67

Hello all,

In my previous post, where I mention that the rear pump pick-up tube is a press fit, I meant that it is a press fit in the rear pump/governor casting (as in the previous post's photo).  Both the front and rear puck-up tubes in the screen (filter) are a slip fit as Greg indicates.

The photo below shows the screen.  The larger hole on the edge of the screen is for the front pump pick-up tube.  The smaller hole toward the rear and on top, is for the rear pump pick-up tube.

Note that the two holes are in two different planes.  Vertical movement of the screen is restricted by the front pump pick-up tube as vertical movement is perpendicular to the axis of the tube where it enters the screen..  Likewise, horizontal movement of the screen is restricted by the axis of the rear pump pick-up tube as horizontal movement of the screen is perpendicular to the axis of the tube where it enters the screen.  Movement of the screen is further restricted by the proximity of the pan once it is in place.  Sorry for any confusion.

Hopefully the OP will chime in again.  Others have provided some good advice, but I think we need some more information to help the OP with his issue.

Respectfully submitted,

Christopher Winter
Christopher Winter
1967 Sedan DeVille hardtop

Perry McComb

Thank you to everyone that replied
It is slipping from 3rd to 4th gear and while it is in 4th gear if I step on the gas pedal in it makes a growl and winds up.

I will try adjusting the bands after the holiday
Thank you all and have a good Holiday

jackworstell

If it is slipping after getting into 4th gear I would first suspect one or both clutch packs are slipping
and this in turn could be oil pressure not high enough.    Remove the plug in the case and hook in a pressure gauge and see how much oil pressure you have.

  Or one or both clutch piston seals
not holding tight ( trans would have to be removed from the car to correct this.)

Once in 4th gear both bands are released.


Jack Worstell       jlwmaster@aol.com

Bobby B

Your answer lies in putting a high pressure gauge on it while driving and monitoring what's going on. It's a simple trans to work on and troubleshoot. Good Luck!
                  Bobby
1947 Cadillac Series 62 Convertible Coupe
1968 Mustang Convertible
1973 Mustang Convertible
1969 Jaguar E-Type Roadster
1971 Datsun 240Z
1979 H-D FLH

Perry McComb

Thanks for the info I will check the pressure with a gauge
This might sound a little strange but the 1946 shop manual says to check the fluid with the fluid warm and the car off
The 48 shop manual says to check the fluid with the car running so I did both when its running it is at least a quart low when the car is turned off it is right on the full mark. So can anyone tell me the correct way to check the fluid ?

Thank you

Perry

jackworstell

Perry

I can see where GM could have calibrated the transmission dip stick  two  ( 1946 vs 1948)  different ways
….either with the engine not running or with the transmission running at idle.

And a one quart difference seems to be about right.

But in the Cadillac parts manual  it shows  part  860.5800 as the dipstick used   1946 thru 1949
( and maybe beyond 1949...my parts manual ends at 1949 ).   This being the case....I don't
see the answer being  the 1946 vs the 1948 dipsticks being calibrated differently

Sorry I can't help.  When you find the answer...please post.

Jack Worstell

Perry McComb

Thanks Jack
So I checked it with a gauge and the pressure is at 80 psi half throttle any suggestions ? should I try the bands next ?

Thanks
Perry