What You Need to Know About High Performance U-Joints Part 2

In our last issue, we discussed the loads placed upon a drag race universal joint. If you recall, even a lower horsepower Sportsman combination can place incredible amounts of torque on a universal joint. Factor in sticky tires and you just know the driveshaft is waiting to take the first exit.

What You Need to Know About High Performance U-Joints Part 2
The workhorse u-joint for most sportsman drag race applications is the 1350 series. This is a non-lubable universal joint, and it is used in all Mark Williams 1350 series driveshafts. Cup diameter is 1-3/16-inch. Width is 3-5/8-inch.

Fair enough, but how do you select a universal joint, and which size universal joint is best for the application? That depends, but according to Mark Williams, the workhorse in their race car driveshafts is the Spicer 1350 joint. In the accompanying photos, you’ll see why. It’s considerably larger than the joints commonly found under a production line car. Naturally, to use one of these joints, the shaft (along with the slip yoke and the rear pinion yoke) has to be changed, but that’s another story.

What You Need to Know About High Performance U-Joints Part 2
Here’s a comparison of the three main types of performance u-joints you will come across. Mark Williams points out: “The Spicer 1350 series has become the standard for virtually all drag racing and NASCAR applications. That said, given the tremendous shock loads generated by more powerful engines, the “stock” u-joints are subject to breakage. To provide racers with the required upgrades, MW developed a series of transmission and differential yokes that utilize 1350 series joints. MW has also developed transmission and differential yokes for use with 1480 series universal joints to suite heavier-duty Pro Mod and similar applications.”

There’s more: At the rear flange, it’s common to use a u-bolt to hold the universal joint in place. But it too has its limits. Mark Williams has come up with a next generation u-bolt kit. The new second generation alloy steel u-bolt kit is a result of information gained from their driveshaft Torsion testing machine. Williams determined that the standard 3/8-inch 1350 u-bolt was prone to cycle failure when cycle testing at high torque levels. The one piece u-bolt allowed the joint to rock out of the differential companion flange.

What You Need to Know About High Performance U-Joints Part 2
You need to attach the u-joint to the pinion yoke (no secret). Standard practice is to use something like a Spicer 1350-series u-bolt kit (first photo), but recently Mark Williams engineered a slick billet steel cap setup (on right).
The new design allows for a more secure attachment at the differential companion flange, significantly improving reliability. This cap setup can be retrofitted to any current style MW pinion yoke. A similar cap is available for MW 1480 series pinion yokes.

The solution was to surround the universal joint cups a full 360 degrees. This allowed the u-bolt to support up to 500 additional foot pounds of torque. Williams’ second gen u-bolt kits incorporate a bubble stud on the rear flange bolt hole, securely indexing the location. The straps are produced from a pre-heat treated Chromium-Molybdenum steel, while the studs are 150K material complete with rolled (not cut) threads. They’re sold as sets with accompanying 12 point reduced double hex nuts, and they fit all current Mark Williams forged billet rear pinion yokes.

What You Need to Know About High Performance U-Joints Part 2
Mark Williams manufactures an extensive range of transmission slip yokes for various gearbox and u-joint combinations. M-W’s “Rapid Release” series of yokes incorporates removable steel caps that can be used when space limitations prevent installations with traditional yokes. The cap design also does an excellent job of securing the U-joint cups.

So what’s the bottom line when it comes to u-joints? Get the driveshaft angles right, keep the pinion angle under control and don’t cheap out when it comes to universal joints. The reliability offered by following this advice can reap major rewards. Don’t get shafted, even if the parts you install are forever hidden from sight.

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