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HomeTech Articles > 993 Technical Article:

Pelican Guest Technical Article
Permission to publish this article is provided generously by
Robin Sun at
Be sure to visit his site for loads of 993 info!

 Transmission fluid change

I changed out my transmission fluids at 28,000 miles to Mobile 1 synthetic 75W90 gear oil. The immediate results of this was a much smoother shifting action.  It was well worth the investment.  The skill level of this DIY from a skill level of 1-10 (10 being the hardest) is a 5.  The only special items you will need besides 4 quarts of gear oil and new washers would be about 5 feet of 3/4" or 7/8" clear vinyl tubing.  I also recommend you get a good quality 10 mm hex socket which can be mounted on a ratchet instead of using an allen wrench. 

(1). Jack the car up on 4 jack stands, please refer to "How to jack your car up" section of my DIY.  Remove the engine undertry and the transmission undertry.  The engine undertray is held on by philips screws, and the transmission undertry need to be pulled out toward the rear of the car once the philips screws are loosen. (Not sure if it is necessary to remove the engine undertry to do this DIY.)

(2). First remove the filler plug, per Ray Calvo's recommendation it is safer for you to remove the filler plug first just in case you drained all the fluid and stripped the filler plug while trying to remove it later.  At this time you will also need to place a drain pan underneath since the transmission fluid will be purring out of the filler plug as soon as you remove it.   Jeff Chan recommends that just to loosen the filler plug first without completely removing, since fluids came pouring out of his filler plug. 

(3)  Loosen the drain plug and drain the transmission fluid.  The transmission drain plug is a magnetic plug that will pick up what ever metal shaving in your transmission during normal driving and shifting.  If there is an excess amount of  metal shavings found on your drain plug I would consult a transmission specialist first before you clean the plug up and put it back on the transmission.  Here are two pictures that shows before and after pictures of the magnetic plug.  The condition of my drain plug at 28,000 miles was normal. Replace the washer and install the drain plug.

(4). Stick the vinyl plastic tube in the filler plug, run the tube through the right side wheel well opening.

(5). Pour 4 quarts of your favorite transmission fluid in the tube slowly and pull out the vinyl tube from the filler hole and install the filler plug with a new washer.  You will need to install the plug quickly, since new fluids will come purring out of the filler plug once you remove the vinyl tubing. 

You are done!   Go for a test drive you will love it!

Important fluid information update May, 2000

As the winter months came the Mobil 1 transmission fluid developed a hard shifting problem in my transmission.  This problem only occurs when the car is cold and the outside temperature is around 35-45 degrees.  During the warm up period I had a terrible time shifting into 1st gear and felt a big bump when shifting to 2nd gear.  But if I double clutch it before shifting to 2nd gear the bump feeling is eliminated.  So the conclusion was that the Mobil 1 fluids were too thick and when it was cold it was not flowing off the syncros fast enough for the sycros to do its work.  But as the transmission warmed up the hard shifting problem went away.  After talking with several Porsche technicians I was told to switch back to good old Dino fluids to see if the situation would improve.  So I drained the fluids out and poured in some Valvoline Dino (fossil) 75W90 gear oil and it did help improve the hard shifting issue when the car was cold, but once warmed up it seems to require more effort for me to shift through all the gears just like before I switched over to Mobil 1 synthetic oil.  I was not satisfied with the result and after talking with someone from "Red line oil" who owns a 993 C4S and had good luck  using a mixture of 3 quart 75w90 and 1 quart 75w80 red line synthetic fluids I too tried this combination.  It did solve some of the problem, but again it is still not as perfect as before when it is cold.  I then recently switched to Swepco 201 gear oil, it is also a 75w90 spec. transmission fluid, but not synthetic.  The Swepco 201s was the thickest of them all, and it made the transmission feel very different.  Almost like a buffer kind of feeling.  I am still having trouble shifting to 1st gear when the transmission is cold, unless I get the car to a complete stop for several seconds I will have trouble put the car in first gear.  But if I shift slowly to 2nd gear when it is cold I can give enough time for the syncros to work and eliminate the grinding sound.   So this is what I am sticking to for now, will see what happens. 

Comments and Suggestions:
JuanC Comments: I change , the brake fluid and the trans fluid , but I have problems when I shift to 2 gear .
March 8, 2015
  Followup from the Pelican Staff: Check if the fluid level is correct. - Nick at Pelican Parts  
Jefrank Comments: For the staff: What is the part number for the plug washer mentioned in the article? It says above it is actually an aluminum sealing ring. Is that the same ring used on the engine oil drain plug? How many are needed to change the transmission fluid and both differentials? Thank you.
July 15, 2014
  Followup from the Pelican Staff: I will have the article updated to reflect the parts. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
Jefrank Comments: Thanks for the information. I have a 1995 993 Carrera 4 which being 4 wheel drive has a front and rear differential. I believe it has three drain plugs. I was told the transmission and both differentials are fed through the same filler plug. I assume I have to remove the drain on each differential and the transmission before filling everything, correct? What is puzzling is my manual says that together the transmission and both differentials take 3.8 quarts. You said you put in 4 quarts and didn't even mention the differentials. I intend to use Swepco 201.
July 15, 2014
  Followup from the Pelican Staff: You will want to remove the drains on each. I would grab a repair manual. It will have the procedure, special tools and torque specs.
- Nick at Pelican Parts
londonlhdcentre Comments: I am using Mobilube 1 SHC 75W90 full synthetic gear oil MOBIL1SHC
December 24, 2013
  Followup from the Pelican Staff: Check the spec in your owners manual. You should be Ok, but double check for yourself. - Nick at Pelican Parts  
londonlhdcentre Comments: I have Mobil1 synthetic 75W90 in the transmission and front diff on my 993 turbo, all seems fine but do you have any comments on having the Mobil1 in the diff?
December 23, 2013
  Followup from the Pelican Staff: As long as the oil spec is right, the brand is really up to you. I like Mobil oil products. - Nick at Pelican Parts  
Don Comments: When I do change the transmission fluid on my 914 what fluid and weight do you recommend and even a brand if you can. I do not need a problem with the shifting when the car is cold. The car is always garaged and has just above 134000 miles on it. I don't ever remember having a problem with the shifting. Of coarse it's not a 993 like the one in the article. I purchased a pump to get the fluid back into the transmission. Maybe I can pump the fluid out in order to lessen the chance of spilling it on my basement floor. What do you recommend on the 914.
December 23, 2013
  Followup from the Pelican Staff: I would replace it every 30k. Give our parts specialists a call at 1-888-280-7799. They can help you find the right oil. - Nick at Pelican Parts  
Don Comments: I just wrote regarding my 914 1973 Porsche and the changing of the transmission fluid. My other question is that I am going to replace the speedometer angle drive at the same time I change the fluid. What is the proper procedure and what problems will I incur when I disconnect the angle drive at the transmission once I have drained the fluid.
December 5, 2013
  Followup from the Pelican Staff: I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
Don Comments: I have a 1973 914 2L which I have owned since 1987. What is the proper procedure to change the transmission fluid and what type of gear oil, brand, and weight would you recommend. What about gaskets and so forth. I think one book from 1976 indicates Castrol oil??
December 5, 2013
  Followup from the Pelican Staff: There should be a fill and drain plug on the side of the transmission. The fill is directly above the drain. Remove them, drain fluid, then fill until fluid trickles out of the fill plug. - Nick at Pelican Parts  
Brendan Comments: I'm the original owner of a '99 996 Carrera manual shifter that experiences difficulty changing from 1st to 2nd, most prominently when the engine's cold. I live in Miami so the temp is pretty uniform throughout the year. I can almost always grate a few gear teeth tips if I shift slowly. The shifter used to be like butter when the car was new but over the past 5 years it's become much more difficult to change gears. I changed the transmission fluid recently with a synthetic but with no difference. Can anyone suggest either an appropriate grade/brand fluid or is the gearbox synchros damaged and require gearbox replacement?
December 7, 2011
  Followup from the Pelican Staff: There is a problem with shifting on these cars, and a detent in the transmission that gets worn out. I have an article on this, but it's not published on the website quite yet. If you drop me an email,, I can email you what I have so far and the fix that we performed on our 996. - Wayne at Pelican Parts  
Mitri Comments: Hi,
About 2 years ago I had a very similar problem with my 2002 BMW X5, 5 speed transmission. I had the original BMW life time fluid in the car and some times in the cold weather it would make a grinding noise upon shifting from 1st to 2nd. I then used the recomended penzoil gear oil and I could not even change from 2nd to 3rd. I thought that I had to change the transmission. After a bit of reaserch I changed the oil to Synchromax from Royal Purple and it was the best thing for the car. The problem was resolved and have not had any problem in 40K miles, even on frezzing temps at Lake Tahoe!!
I will change to the same product in my 95-993 soon!!
December 6, 2010
  Followup from the Pelican Staff: Thanks for the tip! I'm not a huge fan of "lifetime" fluid at all! - Wayne at Pelican Parts  
Marcio Cracel Comments: I have a 2002 Porsche cabriolet tiptronic with 62K miles. The Porsche dealer told me the transmission fluid from the factory is for life. Is that correct? I noticed that my car started shifting in very low speeds. Some times in 5th speed the engine rotation is very bellow of 2k rpm and the car shakes a little bit. Any suggestion? Thanks in advance.
October 29, 2010
  Followup from the Pelican Staff: I don't believe in lifetime fluid, I like to change it, and there are factory procedures to do so. Check out my article here, it's for the Boxster, but it's the same as on the 996: /techarticles/Boxster_Tech/35-TRANS-Auto_Fluid_Change/35-TRANS-Auto_Fluid_Change.htm - Wayne at Pelican Parts  
mburkhart13 Comments: When replacing the filler plug, the above says to "install the filler plug with a new washer". What kind of new washer should be used? Where can I get one?
August 27, 2010
  Followup from the Pelican Staff: The washer is actually an aluminum sealing ring. We sell these in our catalog for a variety of cars. - Wayne at Pelican Parts  
Rob Comments: Hi, I've gotta Giken LSD superlock differential in my '97 993 Cab and I've got 75/120 oil in there because there was a lot of chatter from the gearbox, I still hear a little at times. Giken makes an oil that is 80/250 weight specifically for this LSD and claims that the LSD can be the quietest on the market. I'm wondering how this would affect my shifting and should I just mix in one pint.
May 13, 2010
  Followup from the Pelican Staff: Hi there. For all LSDs, I recommend that you run the oil that the manufacturer recommends. These LSD require that the friction in the gearbox be just right in order for them to operate properly - mixing up the gear lube with another brand or viscosity can significantly change the operating characteristics of the LSD. Too slippery a fluid and it will work more like an open differential. Not slippery enough, and it will lock up more than the designed specs. - Wayne at Pelican Parts  

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