Vibration at 55mph 1800 rpm

[St. Lou]

Hi all!
I'm new to the forum and looking for some help with my '91 Explorer Sport 4.0 AOD (180.000 miles) . Over the last couple of months its developed a vibration at 55mph at 1800 with the overdrive engaged. Any other mph or rpm and everything is OK. I've checked the u-joints and they are OK. Tires are evenly inflated, though worn I'm open to suggestions on what it could be or what to check next. Thanks!

 

[NHale623]

Try and rotate your tires and see if that has any effect.

 

[Gatorblazer]

That issue is common and could be a number of things. It would seem that you may have a transmission mount broken or maybe a motor mount.

Other common areas to check for 1st gen vibrations are the radias arm bushings, warped wheels and the wonderful mystery rear end issue that no one seems to be able fix.

Happy hunting and welcome to the site