Ruckus is last Christmas gift. Son uses it pretty hard. Roll smoothly without the pinion? You mean the gear on the motor shaft?? Haven't tried that and as far as cleaned the diff out. I haven't gotten any further than changing the Spur and motor so I haven't gotten into the diff deep enough to clean it. If there are bearings out, which ones?Is the slipper spring tight? Go tight and then back out 1 to 1 1/2 turns.
Does it spin easy? Try rolling rear drivetrain without the pinion. Maybe you have bearings out. Last time you cleaned inside the diff.
How old is the ruckus?
I'm not sure how much water but sure if it's there he's running through it. I will check it out this weekend and get back to you. Thanks for the direction to look.Yes, remove gear on motor shaft, that is your pinion gear.
You have a few bearings in rear.
If your boy drives in water, dirt, and do not blow it off ever, it makes it's way into the bearings. They gum up, rust, and become hard to spin and lock up.
If you can't roll freely, it is putting stress on the parts that make it move, gears, motor.
Each wheel has 2 bearings on hubs, your rear diff cases have 2 outters. Depending on how much water he drives through will determine if it made it inside to do some damage on the tranny gears/bearings.
So, back to your spur gear, it's doing it's job if you have bearings out.