CVDs, are one of those "must-haves" for anyone serious about racing. They're also a great upgrade for bashers, with more direct power transfer, less drivetrain slop, and no dogbones to eject or wear out. Unlike dogbones or universals, you do have to build CVDs, and because they're an important part of your drive system, it's good to build them right the first time. When assembled properly, you don't have to worry about calling the day early, or a DNF from a dropped cross pin or locked-up CVD.

Words: James Revilla
Issue 139 - June 2007

Difficulty Meter and Tools Required

1.CVDs come in five parts: the axle, driveshaft, coupling, cross pin, and set screw. Get your parts laid out, and make sure you have everything ready, including your hex wrench (the correct size for the set screw) and your thread lock/anti-wear grease.

2. Let's start with the set screw. Place the set screw on your hex wrench and put a small dab of thread lock onto the threads. Don't overdo ita small dab will do, as it will spread around the threads when you install the set screw. With the thread lock in place, insert the set screw into the coupling. Thread it in as far as you can without blocking the cross pin hole.

3. Put a light coat of anti-wear grease (do not use diff grease!) on the coupling's outer surface. You don't need gobs of grease here, as that will only attract dirt and dust and will wear your CVDs prematurely. I like to put a dab of anti-wear grease on the coupling, and then I roll it back and forth between my two fingers to spread the grease lightly across the surface.

4. Insert the coupling into the axle, making sure that the cross pin holes are perpendicular to the axle.

5. Take the driveshaft and place the axle inside the driveshaft cup. Make sure that the cross pin holes on the driveshaft line up to the cross pin hole in the coupler.

6. Now, hold it all together with the cross pin. Insert the cross pin into the driveshaft cup and push it all the way in until the other end meets with the hole on the other side of the driveshaft cup. You might have to wiggle the axle a little to get it perfectly aligned.

7. Hold the cross pin with two fingers so that it stays centered inside the coupling. Angle the axle to gain access to the coupling set screw, and tighten the set screw with your hex wrench. Don't overtighten the set screw, or you risk stripping it out.

8. Most folks are done at this point, but we'll go a step further for a more reliable CVD. Get some shrink tubing that will fit over the driveshaft cup, and trim to size (about 1/2" for anything up to 1/8-scale CVDs). Slide the shrink tubing onto the driveshaft cup, and make sure that it covers both ends of the cross pin, with a tiny bit of shrink tubing overlapping the edge of the driveshaft cup.

9. Using a heat gun or a lighter, shrink the tubing so that it's snug to the driveshaft cup.

Conclusion
The CVDs on your ride constantly spin and change speeds whenever you move the trigger. By building your universals by the book, you can motor on and not have to worry about them. You've now learned how to build CVDs the right way!