Today I finally got my brakes set and I finally was able to play with my truck for the first time in a month. After about three tanks my dogbone fell out of the rear axle and starting binding on the rear axle. This has happened to me several times since I got the truck and have to replace 5 sets of rear axles. Is there any solution to this? I do plan on doing the TMaxx shafts upgrade but then I will also have to get new wheels and tires which will be a little spendy which I don't have the money for yet. Oh also I do have o-rings in my diff cups. Any advice would be great

Make sure there is no play in the dogbone. It should have very little movement back and forth when it is in place. Also, move the wheel to completely stretch out and contract the suspension. Watch the dogbone and see how it is moving. I am guessing at one of the xtremes, the dogbone is moving too much in one of the cups. I had that problem with the ATX and I cut a short piece of fuel tube (maybe 1/8 inch) and put it in the cups where the dog bone fits into. One in the diff outdrive cup and one in the axle cup. This took out the extra movement and fixed my problem. Just make sure your suspension travel is still good afterwards and nothing is binding.

yeah, do the fuel tubing like alvinl says. I had that happen one time and lost the dogbone in the snow []
Also, you can tighten up the balls that go into the end of the A arms. This will bring the wheel hub in closer to the truck so there is less slack in the dogbone. Just make sure to readjust your tie rod afterwards.