Original post by rallyguy condensed to add to the other most applicable thread we had.
I can finally say with some confidence that the below information is correct. I know there will some doubters, and I also know there is going to be a situation somewhere in the world that this information is proven to be incorrect. But, in general, here is truth as I know it.
Driver Side Idler Axle: The 1G AWD idler axle and the turbo Mirage idler axles have the same length, the same splines, the same seal diameters. The diameter of the axle itself, and the mounts are different though. The diameter of the axle doesn't seem to be important since there are 500-600 HP AWD Talons out there using the smaller diameter axles. That means the critical difference is in the mount. The choice of which axle to use is more a combination of engine block and transmission. I dont know which of those two changes, but in my personal situation, it was the engine block! I think that others in this situation are going to find it is more the tranny.
First, the obvious difference in mounts. If you assume that the engine and trans are out of the car and you are looking at the back of the engine where the axle will mount up, you will see 3 bolt holes, all roughly the same height up from the oil pan, each spaced "ABOUT" 2" apart. If you were to mount an Eclipse axle, it would use the center hole, and the one closer to the tranny. If you were to mount a Mirage axle, it would use the center, and the one closer to the timing belt. My experience shows that these dimensions (the 2" dimension) dont change and any axle will bolt to any block. That is the obvious.
The less obvious is the height of the holes. If you took both axles and test fit each on the same car by installing it into the tranny and looking at the mounting holes, you would find that the bolt holes for one of them would not line up. Again, assuming you are looking at the back of the engine, the holes for the eclipse axle are higher (closer to the intake) than the holes that are in the Mirage axle by about .75". Since both use the center hole in the block, this means that one of the two is not going to fit. As I pointed out, in my situation, it appears that the difference is in the block since I previously used an Eclipse axle with this tranny and a different motor, but an eclipse axle no longer fits with this engine. However, based on the large number of swaps out there, I suspect that in many situations swapping the tranny is what may create this confusion.
Word to the wise (or just the swappers out there). Be very careful when swapping to an Eclipse tranny. When you bolt your axle up, the bolts should be lined up almost perfectly. If you have to put any pressure on the axle to get the bolts started, go find another axle. If this is the case, you will still need to use your original CV axle (see below) which is fine because the lengths and splines or both idler axles are the same.
Driver Side CV Axle: They are different lengths, so dont interchange them! Enough said. The difference in length is in the axle, the ends, or cups, are the same and can be interchanged during a rebuild if necessary.
I will add some picture links in a few days.
BTW, I have 5 eclipse axles which are not identical, but the variance is only about .150" (significant, but not an answer to these problems), and I have 3 Mirage axles, each one identical.