Overheating problems on LSP
 

I can get the MM esc to thermal after a few minutes. I have a LSP with a 8XL, running on 4S trakpower 4900, with 16/46 gearing. No fan, but I have a RCM heatsink on the motor, which stays cool enough to hold onto even after hard running. The batteries do not even feel warm. My MM gets smoking hot. I am going to put in a 14t pinion and add a fan. There is no binding in the drivetrain, as it rolls freely. I have all the controls on the MM on their lowest possible settings. The MM rings and the car stops when this happens, I assume it is thermalling.

If I can only go a little while with this setup, will the smaller pinion and fan help much? Is it possible the batteries put out too much power for the esc?

There really is no such thing as batteries being too much for an ESC current-wise. It's the motor that will pull whatever it needs to do the job. If the motor is relatively cool, but ESC is hot, that usually means the gearing is too high. Try smaller pinion and/or larger spur. A fan on the ESC will help the ESC temps, but not the underlying gearing issue...

I had problems with the MM thermalling in my Revo with a 7XL and a higher voltage than 4s Lipo. The fix was a fan over the heatsink. This dropped the MM temp. down to 140-150, and with the fan it NEVER thermalled (as long as the fan was spinning).

That gearing sounds a bit tall for a truck. Try dropping down to 12 or 14T on the pinion and add the fan.

16/46 was what I ran in a buggy on 4S. The tires on the truck are a lot bigger in diameter and weigh a lot more too, so you have to account for that.

Whatever fan you get, 3mm self tapping screws fit perfectly between the fins of the MM controllers.

You have to remember the LSP's diffs are 4.3:1 instead of the standard buggy ratio of 3.31:1