42177 rc conversion transmission cracking+ melted plastic smell

so, ive done a full conversion keeping everything functional even turned the useless DNR into a 2 speed and now the Hi-Lo doesn't wanna do anything but vibrate and melt, without motors pushing the car works fine no crack no melt, i thought the hi lo was pushing itself towards paesanger set so modded for push back, didnt work still crack, running motor super slow do see any issues and cannot see what could be causing it, both hi and lo have this issue, the v6 swap i made thats in the engine...