How to check trans oil level on a '47?

[MartinC]

Sorry for asking what seems to be a very simple question but can someone tell me the correct procedure for checking the oil level on my 1947 60S Hydramatic please?

Also, what is the correct fluid to top up with, is modern GM Auto Trans fluid compatible?

[LeRoy DeVol]

I own a 1947 cadillac 62 sedan, and as much as i love my car the way to check my trans. fluid is very stupid. You have to peel your floor mat back on the passenger side. This will expos the small cap on the hump in the center of the car. After removing the cap you will see the the dip stick. Make sure the car is running in neutral and the stick will tell you the level of fluid. Some people cut a hole in the carpet at this point and install a cap to access the dip stick. I am not sure what the access was from the factory. If your car doesn't leak, you can check the fluid every year.The GM fluid they sell today is OK. 

Lee DeVol

[Raymond919]

If you don't mind, LeRoy, one more question on this subject.

When inserting the dipstick to check the fluid, you insert the dipstick into the tranmission tube and the cap just under the handle of the dipstick touches the top of the fill tube. You can then push on the dipstick an additional 3/8 inch or so to 'seat' it until the cap bottoms on the top of the tube and holds on tight. At which point do you take your reading? Is it when the dipstick cap first touches the fill tube or after you've pushed it down and it securely 'seats'? There is a distance of approximately 3/8 inch which affects the reading.

I hate to ask such a question, but while we're at it and discussing such a fundamental topic, let's eliminate any confusion.
Ray

[MartinC]

Thanks, so engine running in neutral. I assume it should also be at full working temperature and recently run through all gears?

[LeRoy DeVol]

Ray, You should always put the dipstick all the way in when checking fluids. That 3/8" could make almost 1 qt. difference.

[Raymond919]

Yes, LeRoy, that's why I asked the question. I've been doing it wrong and appreciate your correcting me. I have to drain out a bit of fluid now so I will have a correct level. Would too high a level cause 'foaming'?
Thanks, LeRoy, I appreciate your response.
Ray

[kkarrer]

Yes.  The hydra-matic manual for 41 and 48 says that if the fluid level is too high foaming will occur.  It is a pain to peel back the carpet to check it, but at least you don't have to remove the big trans. cover that is secured by about a dozen quarter twenty bolts.  The engine does need to be idling in N and should be checked after 2min. warm up at slowl idle speed. If you check it at high idle (cold) the level on the dipstick will show over full.
Ken Karrer 1941 6227D coupe

[LeRoy DeVol]

Yes there can be problems with to much fluid. That trans. requires 11 quarts of fluid. If you over fill it could foam, or leak out  at the shift lever shaft. Of coarse this depends on the condition of the seals.

Lee DeVol

[49 Convertible]

Gentlemen

I am sorry to upset your apple cart but the transmission for 48 & 49 should be checked idling after warm-up in the DRIVE position not Neutral

[MartinC]

Hmm, so is it Neutral or Drive on a '47?

[Raymond919]

I can only speak for the '49 shop manual which was corrected by the Cadillac Service Department before the end of the model year. They issued a factory "Serviceman Supplement" with the correction.
On page 148 under note 1 it refers to "Adding and Changing Fluid...In step 1-a-5, delete "place the selector lever in Drive range". In step 1-a-6, delete "Drive" and add "Neutral."
It also mentions about the type of transmission fluid and how often it should be changed.
I have no idea if this also refers to the years before or after 1949.
Ray Schuman

[kkarrer]

Here's a quote from page 128 of the Hydra-Matic Drive Shop Manual for 1948...
2.) With the transmission selector lever in "Neutral," run the engine at a speed equivalent to 20 mph for approximately 1 1/2 minutes.
3.) Remove the sheet metal cover over the Hydra-Matic dip -stick from the front floor pan.
4.) Reduce the engine speed to slow idle and measure the fluid level in the transmission with the dip-stick, having wiped it clean.
5.) With  the engine still running at slow idle, and with the selector lever in "Neutral"add fluidto bring the level to the "Full" mark on the dip-stick.  ("Low" to "Full" , marking on the dip-stick equals 1 quart.)

I think the 41 manual says the same thing.  I can't imagine that it was any different for 1947, but I don't have that manual. 
Ken Karrer 1941 6227D coupe

[MartinC]

I wonder if the GM fluid I can get here in Britain is okay, as it's the 'GM Europe' spec for very different cars than in the States.