I have a 1993 bronco that shakes violently when decelerating; braking or leting off the gas. The brakes are fine, the U joints look brand new, the struts are mounted fine, & front end is tight. I honestly can't figure it out! Any helpful suggestions would be appreciated!

 

sounds like you have one very unbalanced driveshaft.

 

If the driveshaft is unbalanced wouldn't it be shaking like that all the time, not just when I'm decelerating?

 

The two driveshafts i had that were out of balance made the truck shake only when i let off the gas or came to a stop and went away above 30 mph.

 

How do I check to see if it is unbalanced?

 

When u say the u joints look new , are they? Only way to competently check them is to pull them off and look at the end caps, bearings etc If your drive shaft was unbalanced that is true . Places to get the shaft balanced would be a fabrication shop . i have a 1985 f-150 and the ford shop checked my u joints (years back) and said the shafts were good , i pulled it off my self to find it wasnt (rusted dust and no grease). good luck TR

 

Are your tires wearing oddly or are they new? It's possible they could be out of balance, slightly, causing you not to notice the vibe at speeds and acceleration.

Also, most all drive shafts are balanced by adding little weights to the outside of the shaft. The weights will be round(coin sized) or rectangular. Make sure you have some(have never seen a driveshaft perfectly balanced,not needing some weight added). The weights are welded to the shaft. They will have small holes in them and the welds will be in the holes. If you look close enough you may be able to see the spots where the welds were if the weights are missing.

How are your brakes? I've seen vibrations due to a high spot in a brake rotor, but this usually causes vibration all the time. But anything is possible.