Why its happening to groups of people at certain tracks: The number one way to cause this damage is nosing in, casing a jump, or lawn darting on a landing or pipe. So, tracks with big jumps (US style Motor Cross tracks) will have twice the number of failures. While we would all like to perfectly land our jumps all the time, inevitably we will case a jump hard and the damage will occur. Once again, after the chassis has a couple gallons on it the chassis flexes more.
Here is whats happening at full chassis flex:
After the last failure I took the center diff out to inspect the drive cup. I found that the drive shaft was wearing quite heavily in the BOTTOM of the cup. I then asked myself; where does all this force go when bottomed out? BINGO, the answer is...... directly into the bearings!!!!! Crush!
(((((Xray's action items that could resolve the issue!))))))
- Shorten the drive shaft. (in my opinion this is the proper fix)
- make the diff cups deeper to allow for more movement.
- or re-work the bulkhead somehow to allow more room for flex.
- re-work the chassis with 4 mill thick version reducing chassis flex.
(((My temporary fix!)))
You can gain more room for movement of the drive shaft inside the center diff drive cup by using a carbide round tip dremel bit, to further concave the bottom of the drive cup. Also move the pin slots deeper so the pins don't receive excessive pressure.
Looks like this when done:
You can gain further room for movement by slightly shortening the ball end on the drive shaft. be sure not to go too far and weaken the shaft end.
Looks like this when done:
This should only take you 15 minutes, and will save you hours of work later replacing the blown out bulkheads and bearings. In the future I hope to see a re-worked front shaft thats a bit shorter from Xray, but for now its Dremel time. Thanks for the read....!
