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Hey gang - 1950 Packard model 2302 w/ Ultramatic here, still running the stock setup for transmission fluid cooling (internal, bottom of the rad). I stumbled on the external trans cooler kit introduced in the Service Counselor No. 26, vol. 6, though most I've talked to about it steered me way from pursuing this kit. Instead, I've been driven toward simply installing an aftermarket cooler in front of the rad. Seems like a cheap, easy, and positive thing to do for the transmission, so I figured why not.

In reading the installation instructions for the external cooler, it mentions running the external cooler in circuit with the OE cooler. I figured I would try to run it this way first - I'm not having any issues with my current cooler leaking into the rad, and cutting it out of the circuit would be easy to do if needed in the future. I would expect you'd want the fluid to go through the internal cooler, then the external cooler, then return to the trans.

After perusing the forum, parts book, and Ultramatic service manual, I can't seem to find which line is the supply and which is the return. The picture is the view from above looking from driver's side fender. I recently departed from the OE lines recently due to some leaking, hence the rubber lines.

Feel free to set me straight if my thinking is off on the approach here. Thanks, everyone!

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For the 55 transmission the output hole was near the top of the trans case however I don't think the cooler connection mattered from the factory. Very likely the 50 transmission is the same arrangement.

I suspect that running them together is suggested because the internal rad mounted also warms the fluid at cold start-up.
With a front exchanger only, may not get to operating temperature and cause sluggish shifting for a while or for the duration. No direct experience, just engr'g practice.

Personally, if your trans is 'overheating' or requiring additional cooling beyond factory, it's due to service/load changes, towing, hilly, etc. or fault in the trans. If that's the case and not just exploring available period options, I'd first opt for a thorough machine cleaning and fluid change depending on the maintenance history. Particulate settles out in the radiator trans coolers, too. Just servicing the trans won't get that and it just recirculates leading to excessive wear.

They did a lot of things in those days that today don't make much sense on inspection. You'll see a lot of new items that come and go each year as the technology was being perfected. Automatics are in their infancy in this period. P was a little more sluggish in that regard with sales lagging expectations while sticking to outmoded, but proven, designs compared to competition. They were more conservative and high end historically.

I've seen a few discussions about Ultramatics and cooling, are they susceptible to over-heating? I have the stock transmission in my 53 Cavalier, and as far as I know it's not running hot, but haven't really checked it either.

I'm guessing that when cruising down the highway the transmission would run similar temps to the engine if everything is working well and maybe run hotter when under higher loads, or if either the transmission or cooling system is in need of maintenance.

Thanks, guys! So, my initial thinking was that I was going to take the OE cooler out of the circuit and just run the external in order to eliminate the risk of the trans and rad fluid mixing at any point in the future. The directions on the cooler I bought suggested running the internal and external cooler in circuit because it "provides maximum cooling efficiency." The directions suggest that running the external cooler alone should be done only when replacing the OE cooler is cost prohibitive.

I would say that I don't get the sense that my transmission is overheating, more just looking at options for "cheap insurance" for the transmission and cooling system. I hadn't considered the two together might be TOO MUCH cooling. Folks who have suggested the external cooler approach have just provided the perspective that it's a better option both for eliminating a potential issue with mixing fluids down the road and cooling the transmission. That said, I didn't really do a deep dive into whether the transmissions are prone to overheating (or just running hotter than they should). Not an engineer here - college band director lol, and just trying to figure out as I go.

As years pass the water type coolers can get deposits over the heat exchanger surface and lose a bit of efficiency so IMO, adding an extra air cooler in series is not a bad thing. I do believe Joe is correct that if both are used, for best cooling the water cooler should be first in line so it could drop the temp a few degrees with the air cooler second and dropping a few more degrees before fluid is returned to the transmission.

I believe the cooling was adequate when new but not spectacular with the water system but with a water cooler fluid could never get lower than the water temperature. Since automatic transmissions have evolved and been farther refined I think it has been established that cooler temperatures (within reason) is better for any automatic transmission. I don't know if Ross does anything to the cooler circuit when he works on a transmission but believe he has advocated adding some air holes in the bellhousing to provide a bit of airflow thru that confined space for more cooling directly to the converter.

For the 50-54 regular Ultramatics the fluid path is slightly different than the late 54 gear start to 55-6 Twin Ultra layout shown above. I do not have any decent photos of the regular Ultras and cannot find any labeled drawings but believe the fluid out of the transmission is at the port on the left side and return is at the port on the rear of the case just above the pan. If Ross or someone else could review that theory and either confirm or correct the port assumption I would not object.

If you do go to an air only cooler be sure to get an adquately sized unit. Ultramatics do produce a lot of heat.

Hey all, quick update.

I tested Howard's hypothesis and confirmed his assumption. I followed what we were assuming was the feed line and disconnected what we assumed was the return at the cooler. I then turned the engine over (the head is off at the moment, so it spins relatively quickly) to see if any fluid would pump out - confirmed that it did. Relative to my picture:

- the top connection (i.e. the inboard connection) is the supply
- the bottom connection (i.e. outboard connection) is the return

I did dive a little further into past posts discussing cooling, and running the cooler in sequence has been brought up as a positive addition for the transmission. One user did mention that they experienced a failure of their Ultramatic after having cut out the OE cooler altogether for an external air cooled unit. In that scenario, the user sat in a traffic jam for an extended period of time, the transmission overheated and required a complete rebuild.

Good point, the in-line cooler would probably provide better cooling when still than a small accessory cooler. Remember than whenever the torque converter is being used, all of the inefficiency is just heat dumped straight into the transmission. This is particularly relevant in driving with lots of long stops, or lots of hills taken at a moderate speed, where the converter is needed for torque multiplication.

I don't think I've heard much from Ross regarding external coolers, but I heard he likes to paint the converter housings black to increase radiative heat transfer.

As for what order to run an external cooler, obviously having the air cooler after the water cooler would drop the temps more, but I doubt it matters much in practice. Already with the water cooler, the temperature is outgoing radiator temperature, which is still cold when the engine is cold, and probably not too warm even at operating temps.

Not sure what's going on here. Car isn't running.
Service councilor 26 is listing for '52, not '50.
There's a complete Ultramatic (700pps) service bulletin covering all years in the literature archive.
Best to start there.

Service councilor 26 is listing for '52, not '50.

SC 26#6 shows the second version cooler for the 23rd series. First version cooler upon Ultramatic introduction in the 23rd series models was in the radiator bottom tank but it proved problematic when leaks and other issues developed. Materials to fix or replace that one were apparently hard to come by during the Korean war so they came up with the second version which was the external frame mounted water cooler shown in the article. Water for that cooler was provided from the outlets used for heater hoses. Materials in the form of a new radiator bottom tank finally became more available to replace the tank version but believe the external cooler became standard for the remainder of the 23 series production. It might have been changed a bit or possibly an aftermarket version was developed because the cooler Joe shows in his post is a bit different from the one in the SC article. The updated final cooler design used until the end came along in 51 with the water cooler mounted on the engine with water supply via the bottom radiator hose..