3906 with an evx2 ESC.. No way to upload pictures. Gribley, I plan on having this turned into an aluminum truck one breakage at a time
Assuming you're speaking of the driveshaft that goes between the transmission and the rear diff... What i did on my 3906 was take the female end of a stock axle (wheel) shaft and fitted it by trimming it so that the entire length of the splined part of the driveshaft was engaged into the female part (IIRC, you'll need to disassemble the bulkhead at the chassis to install it as it won't telescope inward afterward). This seems to about double their strength and basically put an end to broken driveshafts for me (the front one I rarely had an issue with, it was always the rear that broke on mine).
For the axle (wheel) shafts, what worked on my 3906 E-Maxx were MIP CVD shafts (a piece of shrink tubing was needed around the 'bell' end of the MIP shaft to keep the drive pins from falling out though).
FWIW, as I understand it, aluminum will only increase your rate of failure if you (ab)use it hard (the bulkheads themselves being about the only exception to that). Things such as aluminum A-arms & bumpers just bend into twisty little shapes.
I would suggest Traxxas aluminum bulkheads (only), then use RPM plastic parts everywhere else you can if you want to beat on it (the front lower A-arms were a common breakage spot on mine until I went to RPM stuff). RPM stuff flexes and then springs back without breaking.