M5OD/Driveshaft viabration

[tworanger]

I have had a vibration and harshness problem for the past couple years and have been trying to chase it down. the vibration only shows up in 3,4, & 5th gears when accelerating or decelerating(using the engine as a brake). The noise is the loudest between 25-55 mph. The ranger is an extended cab 91-2wd-2.3-M5od-3.73 7.5"axle, i now have 195,000 miles on it. It all started when the clutch got replaced at 160,000 miles, and it was done by a very reputable mechanic. Since then I have rebuilt the tranny & new clutch, new u-joints, new rear axle, different wheels and tires, different transmission, with no change, the issues hasn't gotten any worse either for the past 35,000 miles. The engine doesn't shake or rattle if revved in neutral. So this leaves me with the driveshaft, it is the two piece that i have read is prone to problems and so i checked the center support and bearing, lots of play compared to other rangers with the same design i have checked(i can shake it freely before there is any resistance by the rubber bushing). could this have been the problem all along and it was somehow damaged when the clutch was replaces or maybe this is a result of the vibration, any ideas? I hear that in order to install a one piece shaft from a new ranger i would have to modify the cab floor, any one actually have experience doing this? Thanks for any input and advice

 

[natmanjoh]

i kinda had the same issue with vibrations in my truck. only happened in certain gears, loud roaring with vibrations between 45-65 mph. turned out it was a broken bearing in my rear axle (7.5 at the time) caused by the driveshaft being out of balance. driveshaft had a lot of play at the rear axle connection. i swaped my cv driveshaft for a ujoint shaft out of an explorer, as well as swapping the 7.5 to an 8.8.

since you seem to have done a lot already, i would suggest just having the driveshaft swapped out, make sure you get it balanced before you install it, and see if that solves your problem. process of elimination for vibrations unfortunely. also pop the diff cover and check to see if anything got broken.

maybe someone with more knowledge about mechanics will be more helpful.