Hydraulics!
 

http://www.hobbylinc.com/htm/pgh/pgh2001.htm

Radio control hydraulic kit for 1/25 scale models. I think it will work on an XMOD.

looks like thats way toooo big, thos motors look the same size as xmods and there is no way tey could all fit with that batterry back, not to mention it uses "c" batteries

It is not hydrulics it pulls strings

From looking at it it looks like the batteries and motors go outside the car, in a box, and a series of strings raise and lower the car

In which case, you'd have to disconnect it every time you ran the car anywhere. Wouldn't you have to separate the axles from the chassis anyway? Otherwise it'd just be flipping the body around.