This part makes your Kirby easy to push, and though they are very dependable, eventually they wear out (the G3 is now 20 years old). If you know your transmission is bad, get one, if your not sure read on.
The Power Drive Assembly provides power to the rear wheels. When you Kirby is in drive the force that you apply to the handle is relayed to the power drive which causes the wheels to turn both forward and back to assist you when vacuuming. To see how well your transmission is working, put your Kirby in drive, now place your Kirby on a short carpet or a hard surface, put the nozzle against a wall and your toe behind the Kirby so that it can't move. Now push and pull on the handle and watch the wheels spin. (Please note, this can mar vinyl floors so you may want to place the Kirby on cardboard first) If the wheels spin in both directions when equal forward and backward force is applied to the handle your transmission is good. (It should only take about two pounds pressure to make the wheels spin)
If the wheels did not spin, or only turned in one direction you could have a loose handle pivot spring assembly. This is the assy. that your handle slides into, and transfers your push and pull force to the transmission. If it is not secure you may notice some lateral movement or slop in the upright handle. you may also notice that the pivot assembly slides back and forth with little resistance, in either case it must be adjusted and tightened for the transmission to work. If you will find the Handle Pivot Spring Assy, in my store category "Power Drive and Handle Parts" you will find instructions for adjustment.
This unit comes with a new motor sprocket gear and clip,
I am not affiliated with the Kirby Co. and I know their recommendation would be to seek an authorized service center for repairs, and if you don't feel comfortable getting into your machine, please take your machine to a qualified repairman.
This is a new Genuine Kirby Transmission with Wheels, it will fit any Generation Series Kirby. Replacement of this part requires some mechanical aptitude but no special tools. (A torx driver may be needed for removal) Instructions:
To Remove Cover Assembly and Transmission:
A. Remove the handle, floor nozzle and emptor from power unit.
B. Remove scuff plate by: 1. Remove the screw at the top of the scuff plate for the cord clip. 2. Insert a flat screwdriver into the slot above the switch pedal and lift. 3. While applying downward pressure to the top of the scuff plate carefully slide it to the rear of the power unit. Once the clips at top of scuff plate are free you can lift it off.
C. Remove cover casting by: 1. Raise the headlight cap and remove the two flat screws at the front of the cover casting. 2. Remove two screws at the rear of the cover. (These were under the scuff plate) 3. Lift the cover casting off.
D. Remove the on/off foot pedal by: 1 Inserting a thin flat bladed screwdriver under the pivot points of the on/off pedal and pry them off the pivot pins. 2. Carefully lift the on/off foot pedal up and out of the power unit until sufficient clearance is available to slide the power switch actuating rod out of foot pedal. Leave the rod connected to the power switch.
E: Removing the Transmission: 1 Turn the power unit over, and remove the three screws holding the transmission in. two of the screws are near the back wheels, and the third screw is centered, but is three inches from the back of the power unit. DO NOT remove the center screw that is at the back of the power unit. 2. While supporting the transmission turn the power unit over. 3. Set the N/D pedal in drive. 4. Lower the transmission a little to get some slack in the drive belt, then remove the drive belt. 5. Make sure the power switch actuating rod is pointing upward, then remove the transmission from the power unit.
If you are going to work on your own machine, I recommend a service manual it is a great investment. The manual can be viewed found in "Instructions, Manuals and Tools".
This part retails for $165.00 plus labor, so if you can do it yourself, great, save some money.