A great customer of ours that owns a bunch of business rental properties in Deerfield Beach, Florida called us a couple of weeks ago with an emergency. The driveshaft in his 1994 Ford F-150 broke the u-joint yoke at the rear differential. Luckily, he was only traveling at slow sleep while this happened. Had he been driving on the freeway, he may have been looking at either a totally new drive shaft or at the very least, a new tube, u-joints, and balance.
We can see in the picture that the u-joint hole on his driveshaft yoke is completely busted out. At this point, we've got the yoke machined out and ready to replace with a brand new one.
Since there wasn't any serious visible damage to the tube, the first step was to cut the broken weld yoke out on the lathe. This is a pretty simple process that just involved cutting all the way through the weld to the machined butt of the yoke. In this case, we aren't worried about preserving the yoke but we want to minimize the amount of tubing lost so that the driveshaft doesn't end up too short once we're done.
This is a pretty long drive shaft. Luckily we have a large bore lathe to put the shaft all the way through. This makes driveshaft work much faster and easier.
Once the yoke is fully cut out, we then profile the tubing. This cleans up the place where the yoke was previously welded in and also give us a nice chamfer to help with welding in the replacement yoke. You'll also notice we deburr the inside of the tubing so the new yoke slides in easier.
It's extremely important when we're either building a new driveshaft or rebuilding an existing one that we assemble everything straight. This includes checking the shaft for straightness after it's been welded. Sometimes the welding process can cause the drive shaft to warp slightly and we use heat and water to draw the steel back into spec. Part of getting the parts to go back together straight includes putting a nice profile on the tube in the lathe. This squares everything up so that the machined surface on the drive shaft weld yoke mates up nicely with the end of the tube.
Here, we have the new weld yoke prepped and ready to go into the tube.
In this picture, we've got the new weld yoke nicely welded in place.
With the new weld yoke welded into place in the drive shaft, we check the middle of the tubing and both ends for straightness. If a driveshaft isn't within tolerance, it will both be very difficult to balance (if it can be balanced at all) and it simply won't run properly in the vehicle. This can lead to all sorts of problems like damage to the transmission output shaft and even gear and pinion problems in the rear differential.
Once we've ensured that the shaft is straight, it's time to put in the other new u-joint and get it mounted in the balancer.
This picture came out a little fuzzy but here, we're installing the new 1330 series u-joint in the new weld yoke.
Here's our F-150 drive shaft mounted up in the balancer.
The last step is to get the drive shaft balanced. This ensures that any variations in the metallurgy of the parts don't cause the shaft to vibrate as the vehicle is travelling down the road. Once it's balanced, we paint it for the customer and that's it. Thank you for reading!