Pupp Hays' post forced me to pull my workshop manuals and refresh my thinking.  I went to page 38-02 to 03 and learned something.  I was always of the opinion that a hot check is most accurate.  Per Porsche cold is more accurate.

The three different level indication lines on the fluid tank are: top being maximum level at 80C, middle minimum level at 80C, and bottom line the maximum level at 20C - 30C ATF temp. The amount of ATF between the min and max lines at 80C is 0.2 liters (6.7 US ounces).

If the tank were filled to the top line when the fluid was cold, you would have an overfill situation!!

Specifics are:

ATF level check is carried out at engine idle speed, park brake applied and selector lever at "N".  Car must be on a level surface.

Let engine rune at idle speed 1 to 2 minutes before checking fluid level, so that the torque converter will be full.

ATF can be checked on a cold or warm  transmission, however, the level will be more accurate on a cold transmission (20C to 30C/68F to 86F ATF Temperature) than a warm transmission (80C/175F ATF temperature).  ATF temperature of 80C/176F can only be estimated.

After correcting ATF level to specifications, operate the brake petal, leave selector in each position (R - N - D - N - R) several seconds then return it to "N", so that working pistons of power parts are filled with ATF.  Recheck and, if necessary, correct the ATF level.

If the ATF level is too low, the oil pump will draw in air, which can be heard.  ATF will foam and case incorrect readings when checking the ATF level.  Stop the engine until the foam disappears (approximately 2 minutes).  Add ATF and recheck level.

Excessive ATF must be drained off or drown off, since otherwise transmission components would splash excessively and raise the temperature too much, until finally foamed oil is forced out the vent.  This condition could damage the transmission on a long term basis.
'93 GTS
Charter Member 928 Owners Club

PS: Bad engineering? We do have a transaxle.  Yes, only being able to check and fill the transmission level from the underside is painful, but, the only other option is to cut a hole in the interior somewhere and risk spilling fluid.  Not a good choice either.  Manual transmissions have never been check from the top, why don't we hear griping about that?  How do the new Corvettes address this?


Fellow 928 Auto Trans owners--

A couple posts over the last couple days have discussed auto trans problems with not going into gear and the like.  Owners should be aware that the auto trans is very sensitive to correct fluid level, and that the location of the bottle and the cryptic nature of the markings make it easy to end up with the wrong fluid level.

Your Owner's Manual (Hi Ed!) has a picture of the bottle and the markings on it.  Check the fluid level with the engine running, cycle through all the gears then into park, and the car needs to be on level ground or level on stands when you do all this.  The temperature of the fluid determines which line you get to read.  A trans that's barely warm uses the lower line of the two level marks.

Servicing the trans takes an hour maybe two, and gives you a chance to look for leaks, damaged parts, dust and water spots on the case, and also lets you inspect drive shaft boots, etc while the old fluid is draining.  IIRC, the change interval is 25 or 30k, and may deserve more frequent attention if you drive briskly/aggressively.  No matter, it's a service that's easy to forget until problems or symptoms show up. Try to catch the problems in the symptoms stage and keep your wallet happier.

Again referring to the owner's manuals,  look at the service intervals for the whole car.  Things like wheel bearings, door hinge grease, muffler bearings and the like are often forgotten without the factory schedule and checklist.  Please keep your cars happy and healthy, especially if you have a car I might someday own.  I spend enough time and money fixing my own screw ups, and don't need any extra help.  My guess is that you all feel the same way.

dr bob

This is the correct method to check the level [note, most mechanics won't know where to find the level, let along fill it correctly. It is MUCH easier to fill when on a rack or over a lube pit.

a. Car must be level. With a warm transmission (if you can drive it, go 5 miles or so, if not, let it idle for 10 minutes).

b. Set the parking brake and block the wheels. With the engine running, run the selector through all the gears, then put in in neutral.

c. Scrunch down on the right rear side behind the rear tire. With a flash light check the level in the plastic fluid tank. The tank is at the right rear of transmission, just ahead of the final drive unit. Some models may have a steel shield around it with indicator notches, others, the level is indicated on the  plastic tank. [If you can't see the tank, or if it is dirty, you'll need to jack the car up, tidy it up, then check it].

d. There are 3 level lines, the bottom is the full (min) level when cold, middle is full (min) level when warm, and top notch is full when hot (80C).

e. If it is low, you'll need a squeeze bottle/bulb or a pump to suck the fluid (Dexron III) from the container up onto the plastic tank. If you're jacking the car up from the rear only [use jack stands], DON'T over fill. Squirt in only 8 oz. at a time. You'll need to drop the car back to level ground, restart the engine and run he transmission through the gears and back to neutral. Then check again. [when the engine is off, or when tilted up from the rear, you don't get an accurate level reading]. After several up/down cycles you'll have a full tranny and get your daily exercise.

This will fix this strange trouble. Depending upon the leak rate, remember to check the level every month or you'll be scratching your head again.



On 10/22/00, ""Theo Jenniskens" <jenniskens@wxs.nl>" wrote:
> Hi,
> .........snip.. Am I right is assuming that this is not a problem,
> and that the required fluid level should be between min and
> max markers when hot/running in Neutral as indicated in
> the owners manual? Regardless of the level when the
> engine is off? What indicates an over-filled tranny?
> Thanks for your suggestions and comments.
> Theo
> '88 928s4 cherry red

Hello Theo,

To completely drain the transmission, you must remove a plug on the torque converter and also drain from there.  So that could explain why it didn't take the complete amount.

You are correct, ignore the transmission level when the engine isn't running.  As a matter of fact, Porsche (in their workshop manuals) recommends checking the level when "cold", i.e. 15º - 20 º C / 59º - 86 º F rather than warm at 80 º C / 176 º F.

When checking the level at cold the temperature, just fill it to the bottom line [maximum cold].

'93 GTS


Chris you are correct that after not being started for two weeks or so the fluid level of the ATF is higher than the filler cap on the reservoir . A loose cap or bad seal and it is a major leak ....The ATF does drain out of the torque converter and "overfills" the reservoir . The small diameter hose off the top of the reservoir for later models seems to be a vent . I believe the early cars had a bleed hole in the cap for the reservoir which could also leak small amounts of fluid .


transmission fluid level checking. Researching I’ve found several perspectives on this (checking hot, warm, and cold), however, after carefully reading the WSM (check it cold!), and asking other experts, it’s best to do the following:



So you are ready to do some tranny work? A few tips perhaps?
- Drain the ATF oil
- Get ready for a splash of the remaining oil when you lower the oil pan (precautions?)
- Check the oil pan bottom for anything that looks suspicious
- Have a new seal ring for the plug's), oil pan seal and filter on standby
- Carefully clean everything
- Filling up can be difficult. Several options. A hand-pump and hose is easiest, or even one that attaches to the filler connection (coupler at the side)
- Filling: a poor man solution is a piece of new garden hose, stick it in the reservoir, tape it to the side of the car and use a funnel. Takes time but works ok.
- Do not over tighten the oil pan bolts. 8Nm is like nothing.
- Fill up, run the engine, change gears, fill up again…. Repeat till the tranny is at the 20c mark
- Drive the car and when hot check the oil level in the tranny again.
- Make sure the lid on the reservoir seals nicely.
- Ps: it is easier to add oil than to drain oil ?


1992 928 GTS midnight blue

The Netherlands