ok so heres one for u guys I swapped everything off my big bear to a better frame however now back together the front 4x4 is not work heres whats strang I never pulled axels out of front diff only took motor off and main drive shaft slide out of joint at engine now I bolted everything onto new frame and no front drive but if the quads on jack stands the left front turns until u hold it then right wheel turns which is what its supposed to do but when let down of stands im only getting rear wheel drive any ideas?? even if I put just front end down on ground and rear end up it will not move the front drive shaft is turning the whole time tho also theres no grinding or noise coming from front diff help plz

 

It is many years since I worked on those old Big Bears, but I think the splined prop shaft has circlips on it so you can slide it out to change UJs so, are the circlips on properly? Are the two frames from the same model exactly? As a frame for a switchable 2/4WD bike may be different to the permanent 4WD one.