Transmission cooler for an AT 545

[cadillackid]

when I had an AT545 in my red bus. I have a factory trans gauge on the navistar panel that went to a 2 pin sensor in the side of the pan.. driving it in hot summer over mountains on the east side of the USA I would see temps of 190-200 or so.. sometimes a bit higher when I was stopped.. had It been a heavier bus than my little 6 window bus.. it mightve run hotter...

my other bus is a heavier bus wit ha DT360 and an AT545 and no gauge.. ive run it all over the appalachains, smokies, adriondacks.. 20,000 miles worth since I got it much of it in hot summer and its fluid is still nice N red just like it was when freshly changed as I got the bus.. so its not been killed by heat...

-Christopher

[Tigerman67]

Originally Posted by Booyah45828

On a side note, how many people know what their transmission temps even are? Are you sure you even need a cooler? I'm all for upgrading things but I'm against creating solutions for problems that don't exist.

The reason I state this is because I was in the same boat thinking that I needed additional cooling with my AT545. That is, until I put a gauge on the line outlet from the trans; which comes directly from the torque converter and would be the hottest temp you'd see. Doing this, I realized that I never even came close to seeing the thing get hot. I took a trip this summer down to southern Ohio and the temp gauge never got over 190*F going up and down and around all the hills that I did. Going down the highway, it might have gotten to 140-150.

To be honest, I was more concerned with the engine oil temp. That was mounted before the oil cooler and was 210-220 at times. I think that I'm going to change the EOT sensor location to after the cooler and see what the temp is there. If it's still hot, then I'm going to do something, whether it be the addition of overdrive, another cooler, or a drivetrain swap altogether.

I have a factory dash gauge for trans temp.

Most days the temp is just fine, but pulling up a long grade, it will start heating up fairly quickly and you have to be sure to watch the gauge as its not particularly difficult to push it too hard in those conditions.

I happened to run across a NOS Allison factory gauge with color coding on ebay the other day which I grabbed for cheaper than a typical aftermarket gauge. When I put a cooler in, I plan on adding the allison gauge to output line of the transmission where it is hotest, and relocate the factory sensor either to the return line or the pan (where ever I can mount it). Some factory gauges are/aren't know to be accurate, so I would rather have the dedicated gauge for transmission. Using the factory gauge as a way to see how effective the cooling would be interesting though.

I'm tempted to remove the factory transmission cooler out of the system since I believe it is a loop inside the radiator and if it ever starts leaking, the transmission is done. But concerned that even with a bypass loop, not sure the trans will heat up effectively when its cold without the lap through the coolant to help warm it up and regulate it. As I have heard, running these transmission with the fluid cold and thick will cause you issues as well.

Of course I don't PLAN to be driving that much when its cold out, but who knows.

[Booyah45828]

I would never remove the oil to water cooler in the radiator. The # of btu's that that cooler can remove is way higher then any add on air to oil cooler could even dream of.

[Rivetboy]

Here is the valve ready to bolt in. Note undropped transmission fitting on far left. The sensor is the 190 degree thermoswitch for the fan on the output side of the new cooler. My thoughts are that the thermostat oil valve will put the cooler in the circuit at 190 degrees and if temps are over 190 degrees on the output side of the new cooler the thermoswitch will bring on the fan. There are also two temperature guages one for the supply side and one on the return side of the transmission lines to help determine whether the fan works better as a pusher or a puller.
The brass sensor is abandoned.

Closer and closer

[Rivetboy]

The factory "cooler" is not really a cooler at all It is a heat exchanger to bring the transmission fluid up to coolant temperature quickly. The AT 545 needs warmed coolant to function properly. The clutches are not happy with cold .


If you remove it you run great risks.

[Rivetboy]

Cooler came out good.
Built this gauge today for direct reading oil pressure when the engine has its first start.
Absolutely do not trust that cheap 4 in one gauge on this new motor or the (probably) burnt out oil warning light.. Put a temperature probe in for oil temp on the output side of the oil cooler also not that it is a big deal but just to show differential between the sensor in the oil pan.
Moving on to indexing and installing the driveshaft then put the tailpipe and muffler back in.

[Tango]

Real gauges be good!

[Kaleth2]

Hi Christopher, Sorry for reviving old thread. I think I remember that you also have short bus Cat/545? And installed a cooler on your 545? If so, did you document that or do you know of some detailed instructions on how to do that? This is Kaleth/Karen. We have the 3126B/545 combination. After getting her fixed (new transmission filter and transmission seal in Big Springs) she’s running at a much lower temp. At night, 38 degrees out, 2500rpm, 58mph she was 140 temp. Daytime, 45-50 degrees out, 58, some hills 3-5percent grades that were’nt very long...40 minutes, 2500rpm, 180-190temp. We think a cooler would help with that and we could use her here in Oregon through the Coastal mountains and over the Cascades. She’s only 25 foot and we don’t plan to haul a car or anything.
Thanks! Kaleth/Karen

[cadillackid]

Since I wrote that post above my second at545 died.. nice red fluid and all and that trans broke( I replaced it with mt643).

Both of my shorties are internationals. One with a t444e and Allison 1000(swapped from a busted 545), and a dt360 with mt643(swapped from busted 545).
Those transmissions lasted for awhile in the eastern US mountains but they were never taken on the Rockies or cascades.
Both of those busses just have factory coolers and regular fluid and filter maintenance

[Kaleth2]

Thanks Christopher. Think I saw somewhere someone was getting more life out of their 545 with a cooler....

[Booyah45828]

I don't know if you've ever checked it, but what does the inside of the radiator look like? If it isn't pretty because of crud or corrosion, you might stand to gain some help by flushing/cleaning it out.

Usually that stuff is found by an engine overheat, but it might be worth checking out none the less.

As far as additional coolers go, make sure it's large enough to not restrict flow in the system. Most of your aftermarket automotive coolers will be too small. There's a handful of write ups on here where people installed additional coolers.