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Convertible Top Transmission Gear Replacement
 
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Pelican Technical Article:

Convertible Top Transmission Gear Replacement

Casey Gervig

Time:

2-3 Hours

Tab:

$150 to $250

Talent:

***

Tools:

19 mm socket, 3/8? ratchet, T25 drive socket, drive ratchet, small flat blade screwdriver, 8mm socket, marker or center punch, small brush, electric drill

Applicable Models:

Porsche 986 Boxster (1997-04)
Porsche 986 Boxster S (2000-04)
Porsche 987 Boxster (2005-12)
Porsche 987 Boxster S (2005-12)

Parts Required:

Replacement gear set, cables from motor to transmissions, and any other failed

Hot Tip:

Mark transmission end stops before removing from car, try to determine why gears broke. Do one side at a time.

Performance Gain:

Smooth and quiet functioning convertible top

Complementary Modification:

Replacement of convertible top linkages, and clamshell dampers

The convertible top system on your Boxster has a motor, relay, two transmissions, two cables, various linkages and micro switches. In this article we will go over how to rebuild your convertible top transmissions and replace the cracked or broken worm drive gear. I've always been the type to question authority, so when I found out that you had to replace the complete convertible top transmission because of a broken gear I questioned. Lucky for us, the opportunists at Odometer Gears have come through with an affordable fix to keep your Boxster convertible top going without having to spend $1400 on new transmissions. I began to hear what sounded like the motor was cutting out as the top was opened and closed, and the convertible top light would not go out after closing the top completely. I also found that the reason our gear cracked was that one of the clamshell dampers was seized. Make sure to check for smooth operation of all the components before installing the new gears.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Open the top and put it into service position.
Figure 1

Open the top and put it into service position. (See our article on Boxster convertible top repairs.) You may need to help the top open by pressing the button and pushing the top back gently with your hand. Remove both linkages and the 19mm bolt, which holds the boomerang shaped armature to the left and right side transmissions. Now operate the convertible top button in the closed direction until the motor stops. Mark the position of the indentation (yellow arrow) to the case (green arrow). Do the same for the open direction. This will help us properly orient the micro switch cam when we reassemble the transmission.

Release the cables from the motor by sliding the metal retaining clip (yellow arrow) up off of the cable (green arrows).
Figure 2

Release the cables from the motor by sliding the metal retaining clip (yellow arrow) up off of the cable (green arrows).

Remove the transmissions from the car by removing the three 13mm nuts (green arrows) and unplugging the micro switch electrical connector from the left transmission (yellow arrow).
Figure 3

Remove the transmissions from the car by removing the three 13mm nuts (green arrows) and unplugging the micro switch electrical connector from the left transmission (yellow arrow).

With the transmission removed from the car use a drill (inset picture) connected to the cable to turn the transmission to the closed mark (green arrow).
Figure 4

With the transmission removed from the car use a drill (inset picture) connected to the cable to turn the transmission to the closed mark (green arrow). This will make marking the planetary gears easier.

Next, remove the seven Torx screws (T25) (green arrows), which hold the cover to the transmission case, and remove the cover.
Figure 5

Next, remove the seven Torx screws (T25) (green arrows), which hold the cover to the transmission case, and remove the cover. When you have the cover removed make sure to set the thrust washer aside, which will likely stick to the cover (see inset picture, and yellow arrow).

Mark the two studs (green arrows) with a marker, center punch, or scribe.
Figure 6

Mark the two studs (green arrows) with a marker, center punch, or scribe. This will make sure that the micro switch cam (blue highlighting) goes back in its proper position on reassembly. Also note the position of the ring gear in the housing (yellow arrows), when putting the cover back on this will help line up the ring gear studs to the holes on the cover.

Remove the micro switch.
Figure 7

Remove the micro switch. Make sure to carefully clean the grease from the sensor arm (red arrow). Early Boxsters may not use the micro switch, and the right side transmission does not have the micro switch. If your transmission does not have the micro switch, skip this step.

Remove the center gear (inset picture green arrow), and note the position of the indexing notch (yellow arrow), which indexes the center gear to the micro switch cam.
Figure 8

Remove the center gear (inset picture green arrow), and note the position of the indexing notch (yellow arrow), which indexes the center gear to the micro switch cam.

Remove the micro switch cam (inset picture).
Figure 9

Remove the micro switch cam (inset picture). Now we can see the awesome planetary gear set used to achieve the torque necessary to open the top.

Remove the ring gear.
Figure 10

Remove the ring gear.

Remove the four planetary gears (green arrows).
Figure 11

Remove the four planetary gears (green arrows). These are identical, so there's no need to mark these, but do remember that they are installed this way, with the small gear side facing up.   

Remove the sun gear plate; make sure not to lose the thrust washer (green arrow), which could stick to the back of the sun gear plate, or stay in the housing.
Figure 12

Remove the sun gear plate; make sure not to lose the thrust washer (green arrow), which could stick to the back of the sun gear plate, or stay in the housing.

Now we clearly see the culprit of all our convertible top woes.
Figure 13

Now we clearly see the culprit of all our convertible top woes...the broken gear! Remove the cracked gear from the housing, and set it aside for now.

Remove the axle for the broken gear.
Figure 14

Remove the axle for the broken gear. Make sure to remove the thrust washer (yellow arrow) along with the axle.

Insert a small flat blade screwdriver (green arrows), and gently pry upward while pulling the cable out (yellow arrow) of the housing.
Figure 15

Insert a small flat blade screwdriver (green arrows), and gently pry upward while pulling the cable out (yellow arrow) of the housing.

Lift the worm gear and bushings out of the housing (red arrows).
Figure 16

Lift the worm gear and bushings out of the housing (red arrows). 

Separate the worm gear from the bushings, and make sure to keep track of the thrust washers (green arrows).
Figure 17

Separate the worm gear from the bushings, and make sure to keep track of the thrust washers (green arrows). Now that the parts are all out of the housing it is time to clean up any plastic fragments, and clean all the old sticky grease from the gears and housing. Use a lint free wipe and some brake cleaner in a well-ventilated area. This cleanup step is VERY important to make sure that your new gears last as long as, or longer than the original ones.  

The new gears are made for the left and right transmissions and are not interchangeable.
Figure 18

The new gears are made for the left and right transmissions and are not interchangeable. Make sure that the gear you press in to the hub is the correct gear. The teeth of the gears (red arrows) must go the same way on the new and old gears.

Now that the housing and all the non-broken gears are cleaned up, we can remove the broken plastic gear (green arrow) from the metal hub (yellow arrow).
Figure 19

Now that the housing and all the non-broken gears are cleaned up, we can remove the broken plastic gear (green arrow) from the metal hub (yellow arrow). I found that the easiest way to do this was to clamp the plastic piece in the vise, and then use a screwdriver to break the hub out of the plastic gear by prying up and down (red arrows). 

Once the bulk of the gear was removed from the hub I was left with this little piece of plastic, which was easy to pry off of the hub by using a flat blade screwdriver (red arrow).
Figure 20

Once the bulk of the gear was removed from the hub I was left with this little piece of plastic, which was easy to pry off of the hub by using a flat blade screwdriver (red arrow).

Now simply line up the hub to the pattern in the new gear and snap it in place.
Figure 21

Now simply line up the hub to the pattern in the new gear and snap it in place. I used a press for the first side but realized that I could easily snap the hub in place with my hands. I would recommend using your hands. It is much easier and causes less stress on the gear. If the hub does not go in easily something may be wrong. Make sure that you are pressing the hub in right side up.

Assembly is the reverse of disassembly.
Figure 22

Assembly is the reverse of disassembly. Liberally lather each gear with grease. I used wheel-bearing grease. This shot shows the worm gear and worm wheel gear installed. Do not forget your thrust washers (green arrow)!

A good rule of thumb is grease anywhere that there is metal-to-metal contact.
Figure 23

A good rule of thumb is grease anywhere that there is metal-to-metal contact. This picture shows the sun gear greased between the thrust washer and the gear plate (green arrow). After the transmissions are reassembled, I recommend putting them in the car and operating them a few times, all the way open and all the way closed. Make sure that they sound smooth.   

Then connect the armature and perform the synchronization process.
Figure 24

Then connect the armature and perform the synchronization process. (See our article on Boxster convertible top repairs.) When putting the boomerang shaped armature back on the transmissions make sure that the mark on the armature (yellow arrow) lines up with the indentation on the transmission shaft (green arrow inset). 








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