Defender overheating under bed

[JRSDelorenzo]

We have a 2020 Defender Max HD 10 and can’t get the heat under the bed under control. It got so hot while riding that it caused the rear axle boots to tear. We replaced them and it immediately did it again. Discovered the exhaust had a crack in the Y pipe, which we have since replaced and installed a new exhaust system. We also had a new tune installed which made the engine run cooler. After running it a little while through some smooth trails, the axels are hot to the touch and the boots are hot to the point they feel like they will melt or tear. The plate directly under the exhaust is cool to the touch, so it isn’t the exhaust. Any suggestions on the cause and a fix? 

[Steelslinger]

Check rear end fluid. Might be low

[honda400ex2003]

along with steels note- check your cv joints in your axles, might have bad ones that end up creating a lot of heat.  if they are the only things melting, its more suspect that the axles are messed up rather than extra heat from the engine bay, esp with a tune and such.  theres a lot of other stuff that would be melting that is plastic and closer to the engine than the cv boots.  

steve

[Steelslinger]

You could use a contactless IR thermometer to see what is getting excessively hot to narrow down the area to focus on.

[Andystoy19]

I would suspect that you have a problem with the axles (as mentioned above) or brakes dragging etc. If you have so much heat at the axles you must also be using a lot of throttle. Does the machine coast at all when you let off the throttle or does it stop. You should determine the problem of excessive heat in the driveline before you damage the rear diff etc.

If you replaced the boots before; did you also replace the lubricant if not you will probably need new axles?🤔