Technical Process for adding oil to Hydromatic transmission

Hello all, I've drained the transmission oil from my '48 Cadillac's transmission and now in the process of refilling it. The old oil continued to drain for 3 days and I had at least 1.5 quarts still draining after the end the end of day 1. The car's shop manual says the tranny should take 12.5 quarts of SAE 90 gear oil when refilling. However, after filling no more than 6 quarts, the tranny dipstick is showing that it is quite overfull. I don't know the process of adding oil but is this normal? Should I remove oil, or should I run it to get the level to go down as it circulates through the automatic transmission? I didn't measure how much came out when draining it but it seemed like it could've been upwards of 12 quarts. I only drained it from the large plug on the tranny pan. Any advice would be helpful because I definitely wouldn't want to start it up with too much gear oil and damage something.

 

I believe that you need the pump to fill up the torus as that is where a lot of the fluid is stored. You may have to spin the motor over. I have yet to fill the one I rebuilt so I may be off base. Calling @PhilA

 

Some torque converters have a drain plug as well, check your workshop manual.

 

Drain torus. Drain pan. Pour eight quarts into trans. Place trans. in neutral. Run engine for 1-1/2 mins. just above idle. Reduce engine speed to idle, fill to just below the L mark. Again, run engine to just above idle, but this time for 3 mins. Reduce speed again to idle. Bring level to the F mark on stick.
Good luck!

 

Not that I’ll ever have a dog in the fight, but is it checked while engine is running or off?

 

You need to check it with the engine at idle and you should do it warm after a drive so it’s been through all the gears. When I do auto boxes I top them up, run it up to temp stationary to get it about right then go for a drive and check again

 

Do drain the torus or it will be like dumping 2 or 3 quarts of old fluid in with your new stuff.

 

Well I could be wrong, but a hydromatic takes ATF not 90 weight gear oil, doesn't it?

 

https://forums.cadillaclasalle.club/index.php?topic=174510.0
https://forums.cadillaclasalle.club/index.php?topic=77532.0
looks like it takes about 15 qts of dexron fluid originally type a. Above are a couple links
Dan

 

That’s what I always used in my last Hydramatic.
I’ve never heard of gear oil used in automatics.

 

Dexron III / mercon is available at O'REILLY'S, ok for pre 2006 cars, we use it on early British cars with GM automatics.

 

Don't know where you got SAE 90 for transmission fluid!
48 Cadillac service manual does say SAE 90 for the differential.
Single Range Hydramatic original specs were for Type A ATF.
No longer available. Use Dexron lll /Mercon.
9 Qts or so on a refill, total is around 11 Qts.
Hope you didn't run it yet.

Bill

 

I've used Type F fluid in mine with no ill effects... just put 8 qt's. in my latest one and will top it off when I get the engine running.

 

I did use Type A in my wife's 56 Pontiac's hydro, the modern "backwards compatible" stuff made it shift like crap. I just did a drain and fill so I do not remember how it went years ago and forgot about that when I replied before. We bought this stuff. https://www.amazon.com/Wholesale-Chalet-ATF-Type-1qt/dp/B076DN7BST huge difference in drivability and trans shifting smoothness. I got a second case for my Olds hydro that I have yet to fill.

 

SAE 90 is for a MANUAL TRANSMISSION AKA STICK SHIFT. Not for an automatic. Back in 1948 the only place you could buy the correct ATF was at the Cadillac dealer.

Now you will have to drain and flush and possibly have the transmission rebuilt if the 90 wt got into the clutches. The two pages here from the GM heritage center vehicle information kit for 1948 Cadillac. https://www.gm.com/content/dam/comp...formation-kits/cadillac/1948_Cadillac_VVI.pdf Save that to the favorites on your computer.

 

Who produces Chalet Type A ATF. Would sure like to see a TDS on the product.
Internet search comes up empty, since as far as I know real type A has been discontinued for eons. Had whale oil.

Bill

 

I believe you can drain the “converter”. My stock 55 Olds and the C&O hydro had plugs..

 

The stuff in the link is $20 a quart, must have real whale oil in it at that price.

 

This may have just turned into a really expensive exercise........ Let's hope not.

 

Very helpful, thank you.

 

Yes, let's hope not!

 

Yes, I should've made sure I had my glasses on as I read the shop manual. I must've seen the SAE 90 under the column for the manual transmission. Let's hope I can fully drain what's in there and start over. Luckily I hadn't started the car so hopefully it didn't circulate much.

 

Much appreciated. Thankfully I haven't started the car yet so hopefully I can let it drain for a few days and start over.

 

Very helpful. Thank you sir.

 

Its $100 for a 12 pack case. You can get from same seller on eBay both have free shipping.

https://www.ebay.com/itm/3251239377...b+vCVc5WtlbE6wI1mQctT6KNFx|tkp:Bk9SR8j5kYbbZA

 

I believe that it is simply straight mineral oil with red die and no friction modifiers but I could be totally wrong. @PhilA was doing testing using tractor oil (which I also believe is straight mineral oil and very cheap) on his hydromatic a while ago but I do not know his final results as he got a NORS valve body and that seemed to have fixed his issues. Whatever it is, it fixed all the shifting issues in my wife's wagon. I was so happy that I am the only review on Amazon, and I never leave reviews.

 

Can the transmission be filled with a solvent , stoddard solvent or something similar to remove friction modifiers?then drained and refilled with the proper atf then drained and filled with the correct atf again. After driving change the fluid one more time.
Will using a solvent make matters worse?
Looking on the web a master rebuild kit is 400 to 500 bucks.
Dan

 

Yeah, anyone who has changed a diff filled with 90w knows how well it clings to stuff. I'd drain it and let it sit for a long time then research what solvent is okay to flush the internals (no damage to seal, band and clutch materials). I'd consider filling and draining the solvent a few times.
You made a boo boo, time to find the best solution. I hope you can get it going.

 

After a day or two draining there won't be more than a couple cups left. That shouldn't matter much when diluted by gallons of ATF.

 

Walliemart sells the Type A ATF online. Chalet has a FaceBook page, that leads you here: Download Safety Data Sheets (SDS) | Welcome to AOCUSA. I;m guessing Chalet is a brand for AOCUSA. That SDS service link is out of action, and asks you to call them for SDS's.

Seems weird to have to work that hard to find an SDS for something that is so common.

Cheers,
Harv