One of our 2002 GEMs has had transmission oil leaking into the motor. I have dealt with this before on our 2005 and have noticed a few differences between the two. The 2002 motor is US made and the 2005 is Chinese. The 2002 motor uses a 6203 bearing at the brush end while the 2005 uses a slightly larger 6204 bearing. The trans input bearing on both is a 6005. The motor brushes are also different. 2002 brushes measure 1/2" X 9/16". 2005 brushes measure 1/2" X 1 1/4". Arrowhead Electric in California may have either of these in stock. Knowing all these numbers allows one to have the parts on hand before the motor comes out. Don’t forget to replace the little rubber bushing that goes in the spline end of the motor. Use a pick or small screwdriver to pry out the old one.
When removing the motor, be careful of the four large wires that attach. These are the brushes (thick wires) and the field (thin wires). If the nuts are rusted, DO NOT force them. If forced, the insulator will be damaged along with the internal connection. Just pull the dash, mark each wire, and unhook the opposite end of each wire at the controller. Luckily, the oil could be cleaned out and did not damage the motor. However, several of the studs connecting the brush wires were damaged. Be careful of the clearance between the brush terminal studs and the brush springs. I had to grind down the head of the replacement bolt for clearance (see image). The brush wires can be re-crimped using heavy duty crimp-on electrical connectors (see image). The field terminal wires are solid and therefore cannot be crimped. If one of the field wires broke, I would likely replace the motor, but would save the rotor if it were reusable. A simple way to prevent breaking the studs off would be to replace them with stainless nylon locking nuts BEFORE they rust together. Again, DO NOT force the old nuts if they are stuck. The trick to getting the short 8-32 machine screws back into the bearing retainer ring is to just use a longer 8-32 screw to thread into the retainer, lift it up, and then start the other short screw (see image). Once the first short screw is threaded in loosely, back out the long screw. The second short screw should now reach its thread. Be careful handling the armature because the speed sensor magnet on the end is fragile.
Getting the input bearing out of the transmission is usually not a problem. First, you will need a larger pair of snap ring pliers to get out the snap ring. NAPA #3151 works great. Try not to ding up the aluminum bore where the snap ring rides as this bore is the same diameter as the bearing and dings will make removal difficult. Both times I have used a slide hammer to pull the bearing out and both times, the whole input shaft came out with it. Be careful not to drop the shaft if it comes out suddenly. Check the splines on the shaft for damage. This is not uncommon on a high mileage GEM. These shafts are now available from GEM, but are expensive. A list of part numbers can be found in my post on new and superseded parts. A small three jaw puller is used to remove the bearing. Do not reuse bearings. The Mcmaster-carr number for a 6005 double sealed bearing is: 6661K88. There is not much space between the bearing and the reduction gear by which to get the jaws behind. Check the condition of the o-ring that seals around the outside of the bearing. It is in a groove deep in the bore behind the groove where the snap ring goes. This o-ring measures 3/32 thickness, 1 13/16" ID and 2" OD. The Mcmaster Carr number for this o-ring is 9452K138 for a lifetime supply of 100. be careful not to drop the o-ring inside the transmission. The shaft can be placed in a freezer to make the new bearing easier to install. Be careful if heating the new bearing as it has plastic shields. I have never needed to heat a bearing to install it. If you need to, heat the bearing to 200 degrees F and freeze the shaft in ice, the bearing should then slide right on. Allow the shaft to cool before reinstalling so that the o ring will not melt. Feel for gear engagement when reinserting the the shaft into the transmission. Gently tap the end of the shaft with a rubber hammer to seat it. You will know the shaft is seated when the snap ring can be reinstalled.