The following describes the process of changing the transmission s gear oil in my own 2008 CS 6sp. I have no relationship with any of the products mentioned, other than being a satisfied consumer. Exercise all due care if you consider following any of what you find herein. While I ve tried to accurately convey correct information, your millage may vary, and you are ultimately responsible. Preparations: 1. Select the gear oil. The workshop manual specifies 75w90 synthetic gear oil for the Cayman s manual transmissions. I recommend the product from NEO http://www.neosyntheticoil.com/. I ve used it in two previous vehicles known to be stiff when shifting, particularly when short sifters are installed. In both cases replacing the OEM oil with NEO dramatically improved the situation. It did wonders for my 987.1, too. NEO is not the least expensive oil, but may be one of the best choices. On-line I paid $18.99/qt which included shipping. 2. The manual shows that 2.8 liters is needed to fill the 6 sp (2.25 liters on 5 sp), so I ordered 3 quarts expecting not to be able to drain all of the original oil. However, in the end this wasn t enough oil.
Possible explanations include that the transmission actually holds more, maybe the factory slightly under-fills the gearbox, or possibly the car wasn t completely level when setting on the jack stands. I measured the amount of oil actually drained and found it very close to the specified 2.8 liters, thus suggesting that almost all of the OEM oil did in fact drain out. Regardless the cause, I ended up needing about 8 oz more and so I used Castrol Syntec 75w90 to complete the fill. 3. Consider replacing the OEM drain plug with one that includes a magnet. A strong magnet can capture steel & iron particles and keep them from circulating into places where they might contribute to additional wear. I ordered one from http://www.drainplugmagnets.com/porsche.php who listed its dimensions as M22x1.5x14 (below, left). It came with a sealing ring, plus a spare, and sells for about $35/each. My factory drain plug (above, right) did NOT have a sealing ring installed, but everything I read said one is supposed to have been there. It wasn t leaking, go figure. Prepare the car: 4. I recommend that the transmission be warm to help speed the oil draining out, but not hot from just having been driven. Better to wait about 1 to 2 hours after parking your fully warmed-up car. 5. Access to the transmission s drain plug requires removal of the rear suspension s support plate. This plate should NOT be removed with the vehicle setting on its back tires because the factory says that doing so requires realignment. Therefore, raise the car on a level area and put it on four jack stands of
nearly identical height. Positioned at the normal jacking points. The car just needs to be level and high enough for you to safely work under the back end. You can do all this while waiting on the care to cool. I also suggest urethane lifting (jacking) pads like these that I purchased several years ago on ebay. They do wonders to keep the car stable since they absorb minor height differences, plus also minimize damage to the car. 6. With the car on stands and wheels off the ground you re ready to remove the support plate. There are four bolts that must be removed; two at the front and two are the rear of the plate. Plus two studs on each side that come from the suspension mounts, pass through the support plate, and then through the diagonal braces where nuts are installed. To lower the braces you must also remove all 4 of the nuts on each brace. You also need to loosen the bolt at the front end of each brace near the jack points. Two each side where studs pass through Two bolts at rear Two bolts at front Front-most bolt for diagonal brace. Rear jacking point
7. With both diagonal braces lose you can maneuver and remove the suspension support plate. Mine was partially covered with a thick yellowish looking paint or coating as seen in the photo, above. So were many parts of the suspension. Not completely covered and it wasn t undercoat, but ugly none the less. I found that brake cleaner or lacquer thinner and a rag could be used to remove it. Four studs Diagonal brace 8. Next use a torx #55 to remove the transmission s fill plug that s located on the driver s side of the transmission near where the axle attaches. This will prevent the draining oil from creating a vacuum inside the transmission. I didn t do this and the oil coming out in multiple spurts that contributed to a mess on garage floor. An additional suggestion is to use an open-top drain pan that is 4 or 5 inches deep to better contain the splashes. Transmission fill plug, driver s side Transmission drain plug
Drain and refill the transmission: 9. Use the same torx # 55 to loosen then transmission drain plug that s located at the bottom center of the transmission. This is the same size torx as the 3.4 engine oil drain plug. 10. Position your receptacle to catch the gear oil under the transmission, and then carefully remove the OEM drain plug. Remember the oil can still be hot, so be ready to quickly withdraw your hand, and bringing the drain plug and its old sealing ring out, too. Have a rag or paper towel ready to clean your hands. I suggest you let the old oil continue to drain for at least 10 or 15 minutes. My mess from not having fill plug removed
11. After the gear oil mostly stops dripping you re ready to re-install the drain plug. Use a new sealing washer and carefully tighten with a torque wrench. Remember the case threads are aluminum so go slow as you approach the specified torque; 30 ftlb for the 6sp (19 ftlb for 5sp). If you elected to use the replacement magnetic plug like I did, it comes pre-drilled for the use of a safety wire to further help prevent it from coming loose unexpectedly. With a variable-speed hand drill I slowly drilled a small hole through one of the adjacent cooling fins, and then ran safety wire from the drain plug to the fin. 12. Now you re ready to refill your transmission. There are several ways of accomplishing this tasks, but I like using a long clear vinyl tubing pushed very tightly on to a funnel. The tubing is ¾ inch OD and about 7~8 feet long that I purchased from a local hardware store.
13. Position the funnel a few feet above the transmission and next to the driver s side rear wheel. Run the tubing down through the wheel, over the axel, and in to the transmission s fill hole.
14. The tube should extend about ½ to ¾ inch inside the transmission, basically just past the threads. Be sure to secure the tubing so that it won t accidentally come out of the transmission while you work. 15. Now slowly pour about ¼ of the first quart of gear oil in to the funnel, and then quickly check to be sure the oil is indeed going in to the transmission. Continue filling until you approach what you think will be the full amount. Lift the tubing by the axle to help move most of the gear oil on into the transmission, now pull the tubing out of the transmission keeping the open end up higher to prevent drips. Porsche specifies that a homemade tool be used to check the gear oil level. I used a short piece of stiff wire bent as shown, below.
16. The workshop manual indicates that the 6sp transmission is full when the oil level is 2~3 mm below the fill hole (or 11mm for 5sp, which seems excessively low to me). To check the oil level you stick the tool through the fill hole with the short end pointed down, and while holding the long edge level bring it down to the bottom of the hole so that it lies flat on the threads. Now lift the tool back up and take it out and measure the space as shown below. 17. When you estimate that you re getting close to being full, check the level. Then begin adding oil in smaller increments and checking the level more frequently. Most would agree that being slightly overfilled is better than any amount of under fill, the obvious limit being when gear oil starts running back out of the fill-hole. Some simply fill until the oil actually does run out and call it good. As mentioned earlier, I ended up adding a bit too much oil and the level was almost even with the threads, that s how I left it.
18. Once the transmission is full, reinstall the fill plug using a new sealing ring, and torque it to the same value as the drain plug. 19. You should now be ready to reinstall the support plate, of course all cleaned up and all shinny. 20. I recommend that you reinstall the support plate leaving all the bolts and nuts loose until everything is back in place. Then torque each of the bolts and nuts to 48 ftlb. Don t forget the two bolts at the front of the diagonal braces. 21. Check over everything one last time before carefully lowering the car. After a short test drive check for anything loose or signs of any leakage. 22. Please properly dispose of the used gear oil. 23. Happy motoring.