im getting a noise vibration when in 4h, only on the throutle. when i let off it goes away. it also goes away when i shift back to 2wheel. it a really loud humming noise for lack of better words. i have check the wheel bearings seem fine. axel u-joints are tight changed the diff oil it was dirty but dont think that was ever it, there is a little play it the diff, not sure how much is ok. checked the vaccum switch, i have good vaccum, everthing seem to work fine. about a month ago i replaced my u-joints in the front drive line. i never marked the position of the yoke when took it abart. im thinking that could be the problem? but what i dont understand is everthing turns all the time, so if it was a drive line problem wouldnt i hear or feel it in 2 wheel? anthing else i could check? also anyone have a good source to buy an abs sensor? i broke mine taking the hubs off. thanks matt

 

Your yokes must be phased or it will vibrate, if there is no master spline, pull the yoke off and line it up with the rear yoke, worse case you will be out 180*, if it still vibrates then remove and turn 180*