Question on U-joints

[fordby4]

I tried searching for this but I could not find the answer to my question. So here it is. How can you tell if the u-joints are going bad? I have been hearing a little thump coming from under my x and it sometimes sounds like something is loose and rattling underneath my feet when I am driving. And it sometimes makes a thump when I start up my X. Any help will be appreciated.

 

[savant]

If it's a U-joint, you can get under the truck and wiggle the drive shaft (when the vehicle is parked and off!) about a 1/4 turn back-and-forth. Listen for rattles or thumps. Mine were very obviously bad, it was easy to see that there were no bearings left in my front U-joints. I could see the one half of the joint move a decent amount (1/8th of an inch?) before it would take up the slack left by the dear departed bearings, and begin to move the other half of the joint. This led to a slight bump when I would let off the gas, for example.

Another thing that I've heard can cause thumps and bumps in the front end is a worn out radial arm bushing. There are a number of threads around here on that problem, so search for one of those threads if your U-joint testing shows no problems.

 

[DeRocha]

I'm betting its your radius arm bushings. NONE of the 6 U-joints (part of the front drive line) move Unless you're in 4x4 or have your Hubs Locked. It is more common for the front U-joints in the wheel stub axles to become frozen over time from lack of use... To see how U-joints are replaced check out the link in my sig line.

BTW The radius arm bushings are located in a bracket under your feet.

 

[fordby4]

well i put the t-case in neutral and i turned the front driveshaft with my hand and sure enough there is the sound that I have been hearing.So i think it is the u-joint on the front driveshaft that is faulty. Thanks for all the help.