84FS460 Posted February 12, 2021 Share Posted February 12, 2021 When I engage my 84 F250 in 4x4 and when I'm going up a hill the pickup will do jerking motion or I guess you could say a bumping type motion or feel and feels like it coming from underneath my seat and its random. Is it the chain or gears causing this? Link to comment Share on other sites More sharing options...
Gary Lewis Posted February 12, 2021 Share Posted February 12, 2021 It might be the chain or gears, but I think it is more likely that it is a u-joint. There are u-joints on the rear driveshaft, front driveshaft, and the front axles. U-joints are very prone to failing, so I suspect you have at least one that is bad. Link to comment Share on other sites More sharing options...
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