Transmission fill - 11mm below the plug? Why?
 

Drained and filled my 5-speed gearbox earlier this week. I used full synthetic Walmart Supertech gear lube 75w90. Sorry to say it does seem to be tougher/notchy to shift in cold weather when first starting out. It was about 40 degrees today when I noticed it.

Anyways, what is with Porsche saying 11mm below the fill hole? I tried the little bent paper clip routine and had a hell of a time getting it right. I think I got it but not 100% sure. Since 11mm is hardly anything - anyone ever just fill it until it spills out? Catastrophic failure??? Why didn’t they just locate the hole 11mm lower?

I refilled my ‘04 986S manual transmission to the fill hole over 20,000 miles ago and have not experienced a single issue...first time I’m learning about this. Even in light of this information, I don’t plan to empty any fluid.

I also changed mine last week. I bought 3 liters of the VERY expensive Porsche transmission oil...Just because of the cold shifting issues that some folks here experienced. I went with factory stuff.

Fortunately, I have a friend that works in a repair shop that ordered it for me and got 15% discount.

I had bent a paper clip and scratched the metal for 11mm to emulate a dipstick. Wasn't perfect. I ended up measuring precisely 2,25 liters and poured it by gravity, using a tube & funnel. After I measured with the paperclip, it was about right. Could also touch the oil with my pinky finger...Felt secure. Closed it up. Shifting was fine after that.

Don't know about overfilling issues. I also questioned it a bit but figured that they must have had a reason to specify the level. So I just blindly followed directions.

And saved a few drops of the expensive liquid in the process :-)

I now have a 0,75 L leftover with little use for it .

Me too. I try not to go against the engineers. They know what they are doing and there is a reason for everything they do.

Maybe the 11mm lower level is some sort of a correction for something they found out after the transmission was already designed?

Maybe I can find three other people with .75qt leftover to send me and combine them all. :D

Looks like the 6 speed is supposed to go to the bottom of the hole so I think you are good Htci

I got my 2001 for a song as we thought the gearbox was toast. It was extremely hard to shift into any gear. It felt like all the cables and linkage was frozen or something inside was broken or jammed. I found it has the factory short shift and though that the mechanism was bad, it was fine. Cables? Nice and smooth and fully attached. Adjustment of the cables? No change. With nothing left to lose I decided to go ahead and change the fluid.

When I opened the fill plug, when the car was cold, oil shot out like projectile vomit and made a mess of everything. Strange. I then pulled the drain plug and drained the rest of the oil. Smelled like dinosaur 90w but was clean and free of debris. I could not get my hands on the factory oil here in Japan so I used a local synthetic oil from a Japanese company called Wakos and I did actually fill to about the top of the fill plug. Oh well.

Amazingly, when I got back into drive it was a little stiff until it warmed up but since then it has been slick as &*%$. Didn't need a gearbox after all.

So it was only stiff the first time you drove it with the new fluid and good ever since then?

The six speed is filled until it overflows, the five speed is filled to 11 MM below the plug hole to prevent oil from getting on the clutch through the throw out bearing collar if it is filled higher.

Guess that answers my question... oil on the clutch sounds bad.

I hope I got the level right. I used a white paperclip and made a mark at 11mm with a fine point sharpie. Hard to get it in there because it seemed like there was stuff inside and you had to get the paperclip in just right and not touch any other parts on insertion or removal. Seems like there has to be an easier and more precise way. Overthinking this I’m sure.

Yes, surprised me in a good way. It was 2 years ago this past March.

When I filled mine I carefully measured 2.25 liters, then checked with a bent plastic piece and it was exactly 11mm. However, before I drained it I opened the fill port and some oil came out so I think mine was overfilled before.

I used Mobil 1 DELVAC 75w90 and my 6 spd shifts fine. The fill plug is toward the back of the car driver's side and slightly higher than the drain plug.

The five speed uses a different oil.

My Bentley manual says they both use hypoid 75W90. What is correct for the two different oils? Owners manual doesn’t really say. “101 projects for your porsche boxster” says original porsche oil or delvac 75w90.

Ill probably stick with what I already put in there for now and see how it goes. And maybe end up changing it to genuine porsche oil as I have read on your previous posts most people end up having to do!

I drove the Boxster today and the shifting was good and no issues like the first day after the new gear oil. Hoping I have the same experience as Tommy2

Porsche likes to use full synthetic gear oils that are manufactured to their specifications, which have no API ratings such as Gl-4 as they have never been tested under API/SAE. The oil in the five speed was produced by a Shell subsidiary called “Burma ”, and is unique apparently due to the type of alloy used for the synchronizer rings used in the transmission. The six speed uses a different lube, but again one made for Porsche. Several years ago, we contacted all the major gear oil manufacturers to see is anyone had something comparable, only to be told that they “might have something that could work, but the gear lubricants Porsche uses are unique and we cannot be sure they will work”. And as the lubes are made exclusively for Porsche, you cannot find them anywhere else, and because the Porsche gear oil market is so small, the big company’s are not going to get into competition with Porsche.

Thank you - I really appreciate the comments and sharing your knowledge and experience. You probably don’t remember but I bought my Boxster for cheap with an overheating issue about three years ago and you helped me to diagnose and fix the problem. I probably wouldn’t be driving and enjoying it today without your past help :cheers:

Glad to have been of help.