Yes there is. <a href="http://forum.mtm2.com/viewtopic.php?t=2073" target="_blank">The tip was found by winterkill</a>.
Make your rumble pod file. Then download <a href="http://mtm2.com/~mtmg/downloads/mtm2/utility/podview.zip" target="_self">Podview</a> and unzip it someplace (the mtm2 folder, or traxx folder, any place will do). Double click the podview.exe and open your pod with it. Scroll down until you see a file with the *.SIT extension. It will be in the world folder. It will look like <a href="javascript:void(0)"onClick="window.open('http://mtm2.com/~mtmg/pics/summittest.gif','ohyeah','menubar=no,scrollbars=no,width=583,height=544,left=100,top=10')">this</a>. Write down the name of the sit file, make sure it's exact. Now close everything up, and mount your track in pod.ini
Now start mtm2. Make sure your track shows up in the races screen. Now start a different track. Doesn't matter which one. Use Crazy 98, it's just fine. Now in the game, type <i><b>gold</b></i> (you'll hear a tone), then press <i><b>Ctrl+Y</b></i>, then press <i><b>Z</b></i>, then press <i><b>Ctrl+Y</b></i> again, then press <i><b>Ctrl+L</b></i> (you won't see or hear anything, you have to trust yourself you did it), then type the name of your <i><b>*.SIT</b></i> file (the one you noted above - make sure you include the .SIT part), and finally press enter. Your rumble will load in test drive mode. You only have five minutes of time... and all eight trucks will appear.
Code:
Summary
load a circuit
type GOLD
press CTRL+Y
press Z
press CTRL+Y
press CTRL+L
type yourtrack.sit
press enter
Enjoy