Here we go again - Help! - Transmission overheating

[Daniela]

All,

I can’t believe I have to ask for help again. I really thought I was done with repairs. I did drive my 63 Eldorado a couple of times on side roads and all was good. 
last week I took it out bc it was not as hot. 45min Interstate, a short break and then about 15min back roads with a bit stop and go. 
And all of a sudden the transmission is acting up again. When at a light no power whatsoever in 1st hardly going forward. It then jumped into 2nd as soon as stepped hard enough in the gas pedal and it wasn’t a nice shift. 
So back it is now at the transmission shop. They checked fluids right away and those where all good. Only issue is that only the transmission is too hot. 
the radiator has been re-cored so the transmission shop wants to add another radiator bc he said that would help esp bc the flow in and out was all good according to him. Only the car was not made to withstand modern traffic. 
My issue now is that my dad is totally against it and would rather put a brand new and not reman/recored radiator in. 

long story short: any one has a recommendation or might now what else the issue might be?

Thanks as always

Daniela

[Russ Austin]

I call B.S. on the car not being built for modern traffic. Is the engine running hot?  If it is not, the radiator is working as it should and the trans cooler part of the radiator is fine. I would verify that fluid is moving through the radiator before anything else. 

[Daniela]

Hi Russ, he said 7 pounds in and out. And only the transmission is hot.

[Daniela]

The transmission was at 244F when I had all the issues and then left the car there.

[Daniela]

Oh and I forgot to mention: at one point I was literally not able to put the car in reverse, the lever on the steering wheel moved far enough but it neither shifted not moved the display enough. As soon as I got to the transmission shop it was shifting into reverse just fine. My first guess was that it’s an linkage issue but the mechanic said that there is no way it’s that.
I am just lost and have a feeling he is gaslighting me and to be honest he can tell me anything and I wouldn’t be wiser.

[Jason Edge]

I agree with Russ, If your radiator is keeping the car engine cool, staying say between the 1/4 and 1/2 mark  on temp gage, or or around 190 to 200 degrees F on a digital thermometer, and fluid is flowing as it should from and to the transmission from radiator, replacing the radiator with a new, rebuilt, or good used will probably have no affect. It sounds like something is going on in that transmission to make it heat up like that.  The point is these are very rugged transmissions and were used in just as severe driving conditions if not worse back in the day and almost always good for 100K + miles if fluid was kept filled and reasonably clean.  Whoever rebuilt it should stand behind their work and fix it and not try to make us some driving condition excuse.

[CHRIS CARLSON]

I agree with Russ and Jason. Generally the trans oil temp follows the engine water temp if the trans temp is running hotter then engine temp the trans could be slipping building excessive heat. pull the trans dip stick and check the color of the fluid  it should be bright red not brown,   also smell the oil  if it smells brunt the trans fluid should be changed, but if its slipping you have internal problems. and changing fluid wont help. Sorry to hear your having problems.

[Daniela]

Thank you all - the car is with the guy that rebuilt the transmission and he insists it’s the radiator and won’t even consider it’s something else.

[C. Van Tune]

Hi Daniela,

It's a myth that these Cadillacs were not meant to withstand modern traffic. GM & its Harrison Division (the automotive air conditioning group) engineers would test these cars, and all the big GMs, in places like Death Valley in the summertime, pulling trailers, etc.  They use similar, but much more intense, protocols today. I've been on the GM and Ford and Chrysler "Desert Proving Grounds" many times and can attest to it. 

So, while today's cooling systems are much better engineered and robust in terms of the amount of heat they can "cool", versus in the 1960s, there are ways to keep your vintage Cadillac as cool-running as when it left the factory. 

In no particular order, things to make sure of:

1. Install a freshly cleaned, rodded out or recored stock radiator, with the exact part numbers for your year of Cadillac, A/C or not, etc. It was considered good enough for a Cadillac in a 1964, and the weather hasn't changed that much in 60 years.

(Or you can go large and buy a 5-row aluminum beast, made for cooling bulldozers, and squeeze that in. But, I agree with everyone else that it seems like the trans is your problem.)

Regardless, I'll continue:  

2. Make sure the fan belt is tight enough to prevent slippage.

3. If you have a clutch style radiator fan (those spin freely by hand when engine is cold, but when warm, it locks-up more solid...like pushing against a weight with your hand in water) make sure the clutch is good.

In the clutch types, the clutch will wear, causing not enough grip on the fan hub, so the fan spins slower than it should, which results in poor cooling at slow speeds. If you have a non-clutch fan, then so long as it's bolted securely and there's no belt slip, that's all you can do. (The non-clutch fan was usually installed only on non A/C cars in 1963-64.)

4. At above about 50 mph, radiator fans don't really do much good. The aero force of the wind is more powerful that the fan's blast. So, if your shifting problem goes away (or not) above 50 (or whenever it's a cool/cold day) that will give you a clue as to the problem source.

5. Adding more (or larger capacity) oil coolers, trans coolers, and fans can't hurt, but they should to be mounted in a high-pressure airflow area to be the most effective. Like behind the lower grille.

An added benefit of an additional cooler is that it adds more fluid to the total system being cooled...so that helps spread the heat over a larger surface. Notice that some of the later 1960s-70s Cads even have a loop for power steering cooling...just a metal tubing coming out of the P/S pump, with a couple of cooling fins on it, stuck up into the airflow underhood.

6. Closing up any holes, slots or other open areas all around the radiator (while leaving the radiator as clean and free of anything in front of back of it) is a very helpful method to achieve best airflow. That's why the factory puts all those little strips of foam rubber and air flaps around the radiator support and in any openings around the front suspension, where "bad air" could get trapped, or get routed in the wrong direction.

In a perfect world, you want the air to go smoothly through the radiator, pass through any A/C condensers or fluid coolers mounted in front, and then exit by being pulled rearward by the belt-driven engine cooling fan. From there, it typically is pulled out underneath the car by Venturi effect.

No, car's aren't always well designed for this. Cads of our era for the most part are well designed, because of the large engine compartments and lots of open space around the engine. But, compare that to a 1960s Corvette 427, or even a Lincoln Continental, and it's solid iron top to bottom, side to side. Cad's engineers worked hard to put the major maintenance items (like the distributor) at the front of the engine, and generally made working on these cars easier than other luxury cars of the era.  

7. In working to eradicate unwanted engine compartment/transmission heat, every little bit helps. My motto has always been "A penny (of improvement) here; another penny there. Pretty soon you'll have a dime's worth of improvement." Cooling problems are very often a combination of many little things. This goes for any kind of fluid in your car, but I'm focusing mostly on radiator cooling in these notes. 

8. Getting your automatic transmission to operate in its designed temperature range is a similar task to getting your Cad's engine to run cool, but it's actually simpler. The Turbo 400's fluid is completely contained, so adding an auxiliary cooler is usually pretty straightforward. Heat is created by friction of the internal parts, plus some heat-sinking from the engine and perhaps from an exhaust pipe that's much too close (not typical). There's no "combustion" to add to the heat load, as in an engine. 

But, like an engine, extra transmission heat can be created by vacuum leaks, fluid leaks and fluid levels. As well as worn internal parts (obviously.) So, fix as much of the easy-replacement items as you can (I see you've already done several) like vacuum modulator, gaskets, fluid & filter, etc., before calling in the transmission shop.

9. I'm not a Turbo 400 expert, but I'd recommend getting a shop manual for your car. I have one for every car I own, and it helps to at least learn about what might be causing a problem. Also, buying a mechanical "transmission oil temperature" gauge (it can just be an "oil temp" gauge...exact same item) and temporarily running the gauge inside the car, maybe Velcro'd to the dashboard, will let you have a diagnostic tool to monitor. So you're not just seat-of-the-pantsing-it (my made-up phrase) when you talk to the repair mechanic.   

I'd suggest also searching for YouTube videos from actual vintage car mechanics (not just some yahoo with a popular influencer channel) and look for "curing Turbo 400 overheating" or "how to fix Turbo 400 shift problems" videos. Transmissions look super-complicated, and they are if you don't understand hydraulics and how gears mesh. But, you'll quickly get an idea. From there, unless there's massive wear items inside that you don't know about, it should be straightforward to lower the operating temp, and getting everything running like it should.  

Caveat: I still think that your drivability problems are not be 100% related to temperature. It probably pays a part, but a hot transmission will slip and smell and maybe smoke, it shouldn't rip your head off with a gear change, or sometimes work better, but later not at all. Unless it's totally junk inside, and you'd hope that your transmission shop would've noticed that before now. 

I'd be researching a different transmission shop to take my car to, if I were you. For a second opinion, if nothing else. 

I'm not sure I've answered your question, but I hope that something in there helps. Good luck, and let us know how it turns out. 

Van

[Daniela]

Thank you so much Van! My dad in Germany and I have talked a lot about this and went through all your, Russ and Jason’s comments and the shop manual again and with that we both had a feeling that the mechanic is trying to steer us away from the real problem.
So, I will have another discussion with him on Tuesday and we’ll see what happens next.
I really appreciate everybody taking time to respond to me.

[Doug Scarrow]

   I agree with your comments above . You referenced a Turbo 400 but 63 Cads had the 4 speed Jetaway 315 Hydramtic.

[C. Van Tune]

Doug, sorry...brain misfire. Yes, I'm very aware that the Turbo 400 came out in '64. I read that she has an Eldo and my brain automatically assumed 1964, like my car.  Thanks for pointing it out that the '63 had the Jetaway.