[Justin Stiltner]

Chip,
Having done this just this weekend I can tell you what I did.

You will need to pull or otherwise get the pinion off the FP motor, I had to grind ours down a bit to fit into the puller that we got from bane bots. DO NOT GRAB IT WITH PLIERS AND TRY TO PULL IT OFF, YOU WILL DESTROY THE MOTOR because the force you are putting on it will be transfered to the bushings, etc. in the motor.

After you have the pinion off the FP motor take apart the Planetary 4 screws in the face, and 2 on the motor, careful the entire thing will fall apart.

Now would be a good time to wrap the FP motor with masking tape, this is to keep the metal bits and shavings out of the motor, and yes they will get in there no matter what you try so go ahead and wrap the whole motor, leaving only the shaft accessible.

Carefully measure the length of the shaft on the motor that came with the planetary and carefully mark the FP motor shaft the same length and with a dremel (I tried a band saw, didn't work too well, very dangerous, don't do it) and cutoff disk carefully and very accurately cut the shaft of the FP motor to length being very careful not to heat the shaft up too much as you do. I didn't have a problem with the shaft spinning, but if you have this problem you could hold the back side of the shaft with pliers THROUGH the masking tape. After cutting measure the shaft again, as you don't want to have to pull the pinion off to shorten the shaft more later.

Blow or vacuum the residue off the motor.

Take a file and bevel the edges of the cut edge on the shaft and make sure there are no burrs sticking up from the end, It should be a clean cut. DO NOT FILE OFF THE SPLINES ON THE SHAFT only bevel the end and dress the cut.

Clean the motor off, leaving the masking tape on blow or vacuum the shavings off the motor can and wipe down with a clean paper towel, etc to make sure they are gone.

Take your new pinion(only about 1$ when you order the transmissions) and place your motor in an arbor press (a GOOD vice MAY work if it had smooth jaws and very little slop) making sure that the only contact point on the back of the motor was the shaft, not the plastic or the electrical contacts. Keeping the motor and pinion very straight press the pinion onto the shaft, if it looks crooked stop and look very closely, if the assembly cocks in the press then you could bend the shaft and destroy your motor. I had to stop 3/4 through the pressing and remove shavings from the pinion end to allow further pressing. The pinion should be flush with the end of the motor shaft.

Clean the motor off for the last time and carefully peel the masking tape off (our team leaves the tape over the cooling holes in the motor until just before ship just in case) and reassemble the transmission cleaning the screws off(or replacing with socket head cap screws) and lock tite-ing them. If the end blocks don't seem to be seating onto the round center section or the transmission doesn't turn, or is harder to turn than with the other motor your motor shaft may be too long and need to be shortened. If that happens don't forget the tape!

Hope this helps, and if anyone has a better way feel free to chime in