Hi..newbee to site. Just got a 1999 4x4 and I love it...problem started after 1 week of driving. It is a high pitched rattling noise coming from front passenger side. this started off being just a noise but occasionally shakes the entire truck...its not just a little shake i mean the whole truck is violently shaking. when the shaking first happened it would go away when i hit a bump...hit another bump and it would start happening again. the rattling noise never went away but the shaking would.
i put it in 4x4 high and presto the noise went away as did the shaking and rode perfectly.
i dont want to only drive in 4x4 and would like to resolve this issue.

sidenote: i got the 4x4 high and low light blinking 6 times and truck wouldnt go into 4wd...i disconnected the battery for about 10 minutes..checked all fuses and none blown...reconnected battery and it fixed the issue. im not sure if this is at all related to my above problem but wanted to add it just in case.

Anyone know where i should start or why engaging 4x4 fixes the noise and shaking??

Thank you

__________________
1999 Ford Ranger 4.0L Automatic, 4x4 -- 162,000 miles