Amp Mt won't run on the ground

[SIK-RC]

I have a ECX amp Mt that belongs to my eleven-year-old son he was playing in the backyard it started driving really slow and the battery is fully charged when you lift it off the ground the tires will spend super fast when you put it on the ground it barely wants to move I just put metal gears in it tonight the spur gear looks fine none of the nylon gears were shredded could the brushes in the motor be bad on a stand it will go forward / brake and go in reverse fine but on the ground it just crawls this is why I changed the gears to metal thought they messed up but they were fine I think the esc is fine if its doing all that I mentioned earlier any help would be greatly appreciated

 

[Kolten]

If all else is working could be bad motor.
Spins freely when off the ground but under load does nothing...?
Can you hear the motor turning with the truck on the ground when on the throttle?

 

[SIK-RC]

Yes I can see the gear turning inside the motor the pinion gear and the Spur Gear are spinning while it's on the ground is just moving real slow but the motor sounds like it's going a hundred miles an hour

 

[Kolten]

time to inspect dissect the entire drivetrain from motor to wheels, take your time if you have to tear it down a bit, at least these rigs can be repaired ?

 

[X]

Most likely your slipper clutch is loose and/ or worn out. Look at the nut holding it on, probably needs to be tightened. If so, replace with a new locknut or put Loctite on the threads. Also look at the slipper pad, you might be able to rough it up with sand paper to bring it back to life, but replacement is likely needed.

 

[weave]

I agree with X, it sounds like the slipper clutch. One other thing it could be is the drive wheel hex could be rounded out due to the wheel not fitted to the hex properly.

 

[SIK-RC]

it was broken driveshaft pin

 

[weave]

Yep that wi cause your problem!

 

[John-Luke]

I had the same problem with my sons ecx amp... Took ages to find the problem having dissected everything!... New bearings, clutch, metal gears, 500000 diff oil.... Then finally could see the pin slipping in the plastic part of the axle.... Think metal ones would be better if I could find some.