700 vs. 500 ComparisonBrake Shaft - While there is some difference here it would appear to be attributable to use of the 2 piece Bevel Gear Assembly in one and the one piece bevel gear in the other. More on the bevel gear below.
Counter Shaft - is considerably different. While this is at least partly attributable to the 700 pictured here being off a walk behind Bobcat Mower, which uses bearings to support the outer ends of the shaft as opposed to the normal bushing application there, there is also a considerable difference in diamter of the shaft.
Shift keys are likewise different... 500 key on top, 700 key on bottom.
In looking at the gears pictured here, difference in the size of the Counter Shafts in these two trannies is clearly evident.
Looking at the right end, as pictured or top of the shift fork, you'll note there is also a difference in the shift fork between the 500 and 700.
As indicated above, here we have pictured a two piece and a one piece bevel gear assembly. It should be noted also that the 700 manual does recognize both on at least some trannies, and states that if the bevel gear is replaced with the 2 piece bevel gear assembly, it must be replaced as a set. Cause and reason being, the bevel itself is different on the two.
Looking at the Bevel Pinion, this is more readily apparent, and one should also note the counter shaft gear on the bevel gear assembly is deeper as well.
Input shaft likewise shows considerable difference! Wear on the bottom shaft aside, everything about the Input Shaft is different!!
While there are some subtle differences in the case, again this is somewhat attributable to the bearings used on the countershaft in the 700 trannie. Otherwise there is some difference in the webbing for external mounts, and the bushings and holes in the case would appear to be the same on the Brake Shaft. If you look closely at the second picture, you'll notice there is also quite a bit of difference in the wall thickness surrounding the input shaft.
So for those thinking these trannies are interchangeable... from a perspective of unbolting one, and bolting the other in, yes you can. Externally all dimensions would appear to be the same. Internally however, their parts are not interchangeable!!