Sounds like trouble

Got the truck a few months ago and Ive starting taking my M1078A1 for short trips to see how it drives and I noticed that above 30 MPH there is a grinding that can be heard/felt when I let up off the acceleration. Above 40 MPH the truck is so loud it cant be heard but it also cant be felt. This is the only one ive ever ridden so don't know if its normal hub gears or something more sinister.

Check your driveshaft phasing. Check your hub spider gears. One or both is your problem.

This should be in the LMTV section. It will get more traction there . Guy? @Guyfang

Moved!

Also an unbalanced drive shaft can cause it.

Grinding when you unload the drivetrain sounds like some form of excessive backlash. So could be hub gears, or differential gears…

Hub gear backlash, wheel bearing and CTIS seal service,. Or just get rid of the reductions and install ECO hubs. These trucks have a lot of noise and heat being generated from the hub reductions and many of us have deleted them. It's a much better experience without them. Review the ECO hub thread if you have questions. It's all been covered at great lengths.