1955 Transmission Fluid Change

[Jeff Rosansky CLC #28373]

Greetings all.
I am going to change the transmission fluid in the 55. You always hear horror stories about people changing the fluid in a working transmission and the new fluid killed it. This fluid has been in there at least 20 years so it has to come out. We were only able to jack the rear of the car up and put it in drive and reverse to see that it worked. Other than that I don't think it has been thru its gears in 20 years.
I have a couple of questions.
First, I can't find the front drain for the torus cover as shown in the manual. There is no access hole in the flywheel cover. I don't know if there was a change or if the transmission has been replaced although I have no reason to think so.
Secondly, there is not a filter?
Third,  the car is not ready to run yet. Any problems changing the fluid, dumping new in and not running it?
And lastly, what type of fluid should I use? I have searched this forum, of course, and it appears the Dextron is backwards compatable--but if I am going to make a post about changing the fluid I mite as well ask.
And of course I am open to any other tips and advise anyone has.
Thanks
Jeff

[The Tassie Devil(le)]

G'day Jeff,

I don't usually change the transmission fluid unless it is stinking from being "Burnt".   Or, has a metal-flake appearance when hot.

This stuff doesn't suffer the impurities that engine oil suffers, and lasts for years and years.

Bruce.

PS.   Dexron III is the oil to use if you need to add or change.

PPS.   You will know when it is "Burnt" as it is a horrible smell.   With my Dragster, I used to change the fluid after every 6 passes.

[Bob Kielar]

To change the fluid in the torus you have to remove the starter and the inspection cover. Then you can manually move the engine until the drain plug appears.

Keep Cruzin,
Bob Kielar

[Jeff Rosansky CLC #28373]

Ok, so there is a cover? The book doesn't mention that little tidbit of information. I didn't see any indication of an inspection cover...... but I admit I didn't look to hard. It must not be a small plate because I would have seen that. The starter is off now so this sounds like a good time.
Any issues with just draining and filling without running it?
I see Bruce's post about just leaving it. I am inclined to go that direction but I just don't know what is best.
I have learned a lot over the years but I admit I don't know much about transmissions.
Jeff

[Jon S]

G'day Jeff,

I don't usually change the transmission fluid unless it is stinking from being "Burnt".   Or, has a metal-flake appearance when hot.

This stuff doesn't suffer the impurities that engine oil suffers, and lasts for years and years.

Bruce.

PS.   Dexron III is the oil to use if you need to add or change.

PPS.   You will know when it is "Burnt" as it is a horrible smell.   With my Dragster, I used to change the fluid after every 6 passes.

Totally concur!

[Jeff Rosansky CLC #28373]

This is what the fluid looks like. It smells oily but not burnt.

[The Tassie Devil(le)]

A bit hard to tell by the picture.

Bruce.

[Carl Fielding]

I have logical proof of the following if you need it : CHANGE YOUR TRANSMISSION FLUID AND FILTER IF THERE IS ONE. NOW ! Low hanging fruit. Any rubber vacuum lines if such were used. It has been a very long time since I sold my last '50s Cad. Can't remember what made 'em tick. By the time you are through , you will know more so than most. Assume very little , and remember about timely stitches ! You are the kind of guy I have deepest respect for. I LOVE 4 doors. If they are hanging off a Cadillac , so much the better ! Thanks for saving a tough one , (no where near as tough as that rusty '60 4 door , though) , when you might have been able to take the cheap easy way out ! You guys are heroic brave men !  - Carl

[Roger Zimmermann]

The colorof that oil seems more braun than red. I would replace the fluid and at the same time, remove the lower oil pan from the transmission. It will give an idea about the health of it: probably grey stuff (from the friction disks) and no metallic debris: replace the cleaned pan with a new gasket.

[m-mman]

Uhhhh. . . I am concerned about one statement you have made that others may have missed.
You want to change the fluid . . . . OK that's generally a good thing, However . . .

You said that you do NOT intend to run (operate?) the engine for a while???  Why?

The problem: Once the fluid has been drained from an automatic transmission IT MUST BE OPERATED to achieve the correct level again.
Any fluid added to an automatic trans simply fills up the pan/sump at the bottom. It CANNOT get into the torus (torque converter) without having the engine spin the trans and therefore spin the (front) pump and therefore suck the fluid from the pan into the converter.

From what you have described as your plan, you would end up draining the old fluid and adding maybe 3-4 quarts and the stick would say "full" UNTIL you eventually ran the engine and ONLY THEN would it suck up the added fluid and suddenly the sump would drop to empty.

If you were doing a full service on a running car this is when you would then add the additional quarts (5-8? I dont know the specs on a 55 hydro) one at a time until the stick reads full. You would also then shift through the gears (D, N, L, R) and check the level again AFTER the pump had filled the various servos and clutch packs, etc.

If you add the minimum quarts now and forget to add the additional later then the trans would be operating low and it would not function or possibly cause damage. (running the pump dry)

So again, service is GREAT, but maybe you should elaborate more about what your entire plan is for getting your car going.

[savemy67]

Hello Jeff,

The picture below compares the fluid that came out of my '67 TH400 transmission and new DEXRON III compatible fluid.  I do not know how old the old fluid was.  The car drove and shifted, but the transmission was in need of a rebuild for continued longevity's sake, so I rebuilt the transmission.

Generally, draining a TH400 does not remove all the old fluid.  There is still a fair amount of old fluid in the converter.  The older Hydramatics have a drain plug for the converter/coupler so you should be able to get most of the old fluid out   Hopefully, you have the shop manual for your '55 which should detail the procedure for your transmission.  As m-mman notes, the fluid needs to be circulated through the transmission via the transmission pump.  Be sure you understand how your '55 Hydramatic circulates its fluid (see the shop manual), and keep an eye on the fluid level as you service the transmission.

Respectfully submitted,
Christopher WInter

[Jeff Rosansky CLC #28373]

You said that you do NOT intend to run (operate?) the engine for a while???  Why?

It isn't ready to run yet. The carb kit is back ordered so it is soaking in the corner of the garage. I also have the starter and generator out for rebuild and they are not back yet. The fuel tank is being boiled out and needs to be installed, the fuel lines need to be cleaned out....... Yada Yada yada. I am just trying to get some under the car things done while it is on the jackstands. I intend to pull the oil pan and clean it out but I want to be able to spin the engine with the starter when done so the pump doesn't lose prime.
I have so much to do but I seem to be just hurrying up and waiting. Arghhh!!
Jeff

[m-mman]

Ok, now I understand.
Mechanical skills are important to have to restore a car, but the #1 skill is time management and project management. 

I know it well. Ordering parts on Monday so you can have them by Friday to install on Saturday and Sunday. Stripping and sandblasting the parts by Sunday day, so that you can spray the paint on Sunday night and then have it dry all week so the part is ready to install next Saturday. . . . . Hurry up and wait?  ABSOLUTELY!!!

Car restoration is a juggling act. The stalled, unfinished projects you commonly see offered for sale happen when somebody stopped to wait for 'something" (parts? money?) and then forgot where they were in the process. What had they done? what still needs to be done? A project needs momentum.


Draining the trans/converter now and replacing the gaskets now with the idea to refill things 'later' is fine. You do not have to worry about the trans pumps (or even the engine) losing its prime. Draining oils from a 'pan' always leaves a little residual in the pump (you cant get it all out) such that it will draw in oil next time you operate it.

Let it sit for years after draining?? Remove, wash and install a DRY pump? These might cause issues with needing priming but from what you describe you should be OK.

The DANGER with your plan is FORGETTING to refill (top off) things when you fire it up again. . . .

I currently have a car I am doing. New/rebuilt or cleaned; motor, trans, rear end, brakes etc.  I removed  everything for service and painting (springs, suspension, fuel tank, etc.) and now have all the shinny parts bolted back in place. HOWEVER, Because I might have to remove a part again for some unknown reason (driveshaft? axles? touch up painting?) everything is currently DRY, nothing has been refilled. (including the brake system) I too am ordering and waiting on starters, alternators, radiators, powder coated core supports and such.

I worry constantly that I will get excited and get ahead of myself after installing all the engine accessories and fire up the engine WITHOUT adding the trans fluid or refilling the P/S. Perhaps the more I worry the more I will remember when the time comes, but yeah, forgetting to add the fluids would be very embarrassing, and very destructive.

[Jeff Rosansky CLC #28373]

I know what you mean. Anything can be forgotten. I am a tape a checklist to the windshield kind of guy. Have even put tape over the ignition switch.
This is my second project--however not as involved as yours. I had a plan in my head (and written down) but that is falling thru.
I am just concerned about leaving the system (oil mostly) dry for a few days. I had hoped to clean the pan and then prime the system with the starter. But the guy doing the starter is behind. I know I can spin the oil pump thru the distributor but it is in the back and I am short!
And to top it all off, I have the red 70 in a different location while I am doing this. It has been beautiful the last couple of days so I have been driving it....... and it poured last nite. Weatherman didn't predict that. Oh well, they got wet when they were new, right??
Patience Jeff, patience.

[moto1969]

My 55' cadillac Coupe Series 62 sat for 25 years and decided not to change the fluid because it did not smell burned and the color is reddish-pink.  I warmed up the car and checked the fluid level as directed.  No problems as I tested all the gears and did not need transmission fluid.  Thanks for building my case for not changing the transmission fluid.