Just got my Bronco! Got some questions...

[McLeod]

To the OP: Even though you know what ABS pulsating is like, you should disconnect the ABS to verify. When the ABS is disconnected/fails, the system resorts to a basic brake system.

[greystreak92]

The "Ball" is referred to as the "centering ball" since that is what it does! It keeps pressure on both cardons or "spiders" or whatever familiar term folks use for the center section of a universal joint. (Hence the term "double cardon universal joint" which is what the front of the rear driveshaft on every Bronco has).

When the centering ball gets old and worn along with the two cardons the entire assembly gets sloppy and begins to lose its ability to maintain proper geometry. Basically what you have in this setup is a U-joint with nearly TWICE the flexibility of a standard U-joint because of the second cardon. The double-ended yoke is actually a very short section of driveshaft that need no additional support because the centering ball creates enough pressure between the two cardons to keep them from flopping around like they would if they had no support in there. When these components get worn they begin to wobble like a two piece driveshaft would if it had no carrier bearing.

Yes, essentially the rear driveshaft is a two-piece unit that requires no carrier bearing because of the double-cardon U-joint with this centering ball setup.

[helirich]

I would agree with Greystreak except it needs further explaing. The carden joint is not like a short driveshaft, but like a constant voloscity joint.

In a conventional driveshaft (like on the front axle) you have the t/case output shaft, the driveshaft and the pinion. If for a moment you imagine the three all in a straight line. If the t/case turns at 2000 rpm, the other two also will turn at 2000 rpm.

Now imagine the t/case output shaft and pinion paralell, but five inches apart. (like in front) If the t/case shaft turns 2000, the driveshaft will turn at 2020 rpm for one quarter turn. Then it will turn at 1980 rpm for one quarter turn. The driveshaft will excellerate and de-excellerate twice ever revolution. This speed differnce will be greater the steeper you make the u-joint angles. If your u-joints are correctlly clocked though, the pinion will still turn at a constant 2000 rpm.

Obviouslly, this creates some vibration. But if you have the u-joints clocked 90 degrees out, (worse case) instead of the pinion getting averaged out, it would get worse. IE: the pinion would be turning 2040 and 1960 rpms. This would cause alot of vibration, not to mention an early failure of some component in the system.

There is also a problem if the pinion is not paralell to the t/case shaft. It will do the same thing to a lessor extent. This is a common problem on lifted trucks that dont put in the correct wedge on the leaf springs.

Now the carden joint will spin the same speed as the t/case shaft no matter how much you bend it. It is a constant voloscity joint. If you notice, the rear diff is pointed to the carden. So the driveshaft is turning the same speed as both ends like in my first example. What this does is allows the whole system to turn a constant 2000 rpm. Thats why they did this.

I guess the moral of this story is if you have a carden, point the diff at it. If you dont have one, the diff should be paralell to the output shaft.

Man, I can get long winded.

[00blkexplorer]

Well I replaced the center ball and everything works great!

Just a couple things here and there and my truck would be good as new. Thanks for all the help guys!