Many drivers use ice in their liquid cooled transmission coolers. The idea makes sense—ice absorbs heat as it melts, so it should help keep temps down.
And it does work.
But it doesn’t work the way people think it does.
The first thing to keep in mind is the cooler only holds so much. You’re working with a fixed volume no matter what you put in it.
Ice actually puts you at a disadvantage there.
Ice is less dense than water, so if you fill a cooler with ice, you’re fitting less total mass into that space than if it were just full of water. So even though ice absorbs heat when it melts, you’re starting with less material overall.
After the ice melts, now you’ve just got water anyway.
And in real derby conditions, things get hot enough that the water doesn’t just sit there—it boils. It’s pretty common to see coolers boiling off by the end of a run.
Boiling water moves a LOT of heat. Way more than melting it and warming it up.
So what’s actually happening is:
Ice helps slow the temperature rise early on, but once everything gets hot, the cooling is mostly coming from water boiling off—not from the ice you started with.
At that point, the system is limited by how much total material you have in the cooler and how fast it can shed heat, not how cold it started.
So ice isn’t useless. It works, especially for short heats and features.
I just don’t think packing in as much ice as possible is the advantage people assume it is.
To put some numbers to it:
Take the same cooler filled two different ways.
- Packed with ice: about 57.5 lbs
- Filled with water: about 62.5 lbs
So right away, the ice setup has less total mass to work with.
Now look at the phase changes:
- Melting ice: 144 BTU per lb
- Warming water from 32 to 212 degrees: 180 BTU per lb
- Boiling water: 970 BTU per lb
So boiling removes roughly 6.5× more heat per pound than melting ice.
Which means once things get hot:
The system is doing most of its cooling through boiling water, not melting ice.
And since the ice setup started with less total mass to begin with, it doesn’t really gain anything long-term—it just delays the inevitable for a short time.
That’s really the tradeoff.
The ideal water tank transmission cooler should start with just enough ice to start with cool as close to 32F water as possible. Any more than that and you are just wasting money on ice.
I wrote about this a few years ago with a lot more of the math built out here:
derbytime.net 