Welding in U-Joint Caps
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By: Terry L. Howe - 8/2001

A Dana 44 short side shaft from a late 70s full size Cherokee.
Detail of the tack weld on the universal joint cap

If you are finding your Dana 44 front axle upgrade just isn't cutting it or you can't afford a front axle upgrade, welding in the u-joint caps can help. Welding in the caps helps saves both axle shafts from being damaged and it provides an early warning system.

Save the Shafts

Welding in the caps can save the shafts for future use. If a u-joint fails and the caps are welded in, the caps are less likely to pop out and hit the ball joint. Once the caps hit the ball joint, normally the yokes from both shafts will stretch making both shafts useless. With Dana 44 axle shafts, I normally see about twenty u-joint failures for ever one axle shaft failure, so the u-joints are really the weak link. It doesn't matter if you are running junk yard shafts or high dollar after-market shafts, the u-joints are almost always the part that fails. If the upper ball joint is hit with a cap that has walked out, the whole knuckle can pop off, which is real unpleasant. If the knuckle comes off, both shafts are normally ruined and the tie rod breaks.

Early Warning

The welded in caps are great at providing an early warning system to axle failure. Once the weld breaks, you know it is time to replace the shaft. The weld breaks when the cap starts to get pushed out or the yoke stretches. If the shaft is replaced early, the damage can be greatly reduced.

How it is Done

The key to welding in the caps is weld enough material to hold the cap in place, but not hurt the operation of the universal joint. All that is required is a tack weld on the edge of the cap. The best place is in the middle closest to the splined end. The outside of the yoke is the weakest part and you don't want to damage the strength of it. If you weld on the sides, it can interfere with the installation of the shaft (unless you have Ford knuckles and spindles). Most Jeep and Chevy knuckles and spindles have just enough room to install the shaft and a tack weld on the outside would make it difficult to impossible to install or remove the shaft. The weld should be as close to the splined end as possible.

Reusing the Shafts

If the other side of the shaft breaks or the u-joint breaks, the tack weld can be ground down with an angle grinder to remove the cap. When a new cap is welded in, any material that was ground away will be replaced. There are a limited number of times you will want to reuse the shafts. Even if a shaft doesn't break, only the other shaft breaks or the u-joint breaks, the yokes will stretch a little. The more times you reuse a shaft that has been in a past break, the more times you will break. A slightly stretched shaft is more likely to have a cap bind up or crack the weld. Once the weld is broken on a shaft that has a stretched yoke, the cap will walk out and make fatal contact with the ball joint. If the caps slide right in the yoke and don't require any hammering to install, throw the shaft away.

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