The Erevo trans is the same whether it's the brushed model or the brushless model. Either way they're basically bulletproof. But there could be some binding and an easy way to check is to simply remove the pinions from the motors. Then you can roll the truck, rotate wheels individually, rotate both the front wheels together, then the rear, listening and feeling for anything funky in the drivetrain without the motors interfering.

The most likely source of any binding though is the pinion to spur gear mesh. Many people just can't get this right and if they didn't care because they were selling it the mesh could be off. But before you put those pinions back on check the size (spur too) and compare to the manual which is available online at Traxxas.com. The previous owner could've geared for a higher top speed increasing the load on the motors making them run hotter. If the tires are much heavier and taller than stock they could also have an effect. I've never ran a brushed Erevo but from what I've read they're slightly overgeared from the factory and to keep them cool you need to drop about 2 teeth on the pinions compared to stock. Also in the manual is how to adjust the slipper clutch, if it's slipping excessively the motors could be getting hot from that. Adjust according to the instructions although I recommend going about 1/8 turn tighter than the instructions.