MIP CVD's (Constant Velocity Drives)

Potential Sources Of Problems

Constant Velocity Drives, or CVD's as they are commonly called, are a source or great controversy. Some people swear by them, while others swear at them. I am in the former category, as my experiences with them on my Electric Stampedes has been problem free. However I do think that MIP has room for improvement with their product. For my full review on them, see the MIP CVD review in the reviews section of my site.

Below I've focused on a couple of problem areas others have experienced with their CVD's and some ways to avoid these pitfalls.

Decreased Shock Travel

One of the more common problems I hear about with CVD's, is a loss of shock travel in some cases. How much, or whether you see this, depends on the exact shock and suspension configuration of your Stampede. If you do experience a limitation in shock travel it is only a millimeter or two. However a much greater concern with this problem, is what might happen when the dogbone and the output yoke strike one another. The result can sometimes be a bent dogbone. To prevent contact from occurring, use the tubing limiters mentioned in my section on Shock Strengthening.

Another possible problem that can sometimes cause a travel limitation is the Phillips head screw that fits in the end of the output yoke. When using the older style stock plastic yokes there is a small screw that fits in the end of the output yoke. The screw is pictured alongside a CVD output yoke below. Note that the new style of the Traxxas stock output yoke, that uses a single pin instead of the two grub screws, no longer uses this small screw.

This screw should not be used with the CVD's. All you need is a little lock-tite on the grub screws, then follow that up by tightening the grub screws down.

Broken Dogbone

Most of the time this is caused by one factor, poor maintenance. What happens is that the grub screw that secures the cross pin, which holds the dogbone and axle together, can become loose over time. When this occurs the pin slides out as the dogbone spins at what is usually a very high RPM rate. Once the pin slides out enough it will catch on the suspension arm. What usually occurs in this scenario, is the hole the pin fits into takes the punishment, and the dogbone breaks at that point. Below is a picture of what the pin would look like as it is sliding out.

There are a couple of things you can do to help with this situation. All I do is use lock-tite on the grub screw that secures the pin, and then cover the entire joint with some shrink tubing as shown below. The tubing will help hold the pin in place should the grub screw work it's way loose. The shrink tubing should hold long enough to catch the problem in your post-bash inspection. If you examine closely, and the pin is loose, you'll notice the pin making an indention in the shrink tubing when this occurs.

If you want to take it a step further, you can use these CVD Bulletproofing Methods to further insulate yourself from this potential problem. However let me stress that none of these solutions is a substitute for inspecting your CVD's at the end of a bashing session or race. As with anything, proper maintenance is crucial to help avoid potential problems down the road. Also it's important to allow all the lock-tite on all grub screws to fully cure before using the CVD's. Otherwise you may run into a problems with a grub screw backing out as well because the lock-tite won't hold. Consult your lock-tite tube for recommended curing times.

Grub Screws That Will Not Tighten

This is an easy fix. The first thing you should do, when buying a set of MIP CVD's, is to throw away the hex wrenches that come in the set. They are made of very cheap material and most of the time strip before you even finish assembling the axles. Go buy a quality set, or just pick up the two hex wrenches you will need for the job. The two sizes you'll need for the MIP CVD's are a 1/16, and a .050 hex wrench.

Part One:	Potential Sources Of Problems
Part Two:	Installation