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Disappearing Transmission Lube Oil

After a diligent search of the forum with nothing similar found:

86 930, 43,000 miles, I have owned it almost a year. Car is all original.

4-6 months ago, while the car was on the rack, I decided to check the trans lube.
It was down, well below the "stick your finger in the fill hole and bend downward to check level" test. I diligently filled the transmission with 75W-90 gear lube.

Fast forward to today, I'm changing engine oil, decided to check trans oil while I'm there. Guess what? No oil on the test finger again. What? There is no evidence of any transmission leak at all. Nowhere forward of the engine/transmission interface that I can see.

There IS a pretty good engine oil leak, seems to be coming from the bottom of the engine case, about half way back. Its coating many of the hoses and metal parts aft of the centerline of the engine.

Any thoughts as to where the trans oil might be going? Answers that include more than three spatial dimensions not accepted!

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1986 930, Garnet Red Metallic
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63 904 (086), 63 904 (038)
70 914-6
Old 06-17-2013, 03:12 PM
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It's probably going out of the top mounted breather in the form of gas/vapor/mist (maybe) . . .

Last edited by Ronnie's.930; 06-17-2013 at 03:28 PM..
Old 06-17-2013, 03:17 PM
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CFD CFD is offline
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What way is the vent on top facing? I had a prob where I was losing oil out the vent and discovered it was facing rearward - turned it forward to the correct angle and problem solved. It was coating my engine cases with oil as well. Perhaps worth a look?...
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Old 06-17-2013, 03:20 PM
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Ronnie beat me to it...!!
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Old 06-17-2013, 03:21 PM
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Quote:
Originally Posted by Telerding View Post
After a diligent search of the forum with nothing similar found:

4-6 months ago, while the car was on the rack, I decided to check the trans lube.
It was down, well below the "stick your finger in the fill hole and bend downward to check level" test. I diligently filled the transmission with 75W-90 gear lube.

Fast forward to today, I'm changing engine oil, decided to check trans oil while I'm there. Guess what? No oil on the test finger again.
I found (that with refilling a 915 trans) that fresh thick 75/90 gear oil takes a while to seep into the outer reaches of the transmission.

I had drained about 2 litres into my waste bottle, but after refilling with one & half litres, no more would go in, this was puzzling - so I left it for a few days to settle. When I checked again the fluid level had fell & I was able to put the rest of the oil in.
Old 06-17-2013, 03:40 PM
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This is very interesting as I had a transmission totally destroyed due to overheating from low fluid on a 85 930 with over 500HP. I was really ticked off as it had been to 2 different shops for other repairs before I bought it and one shop for a dyno tune I had done. I had wondered who forgot to refill if they drained it or WTF happened. It had only 6000 miles on the rebuild of both motor and trans, however I only put on about 600 miles before the trans got real noisy on the dyno. It really was not to noisy when on the road as some race transmissions make more gear noise than stock and being more of a track car it had no mufflers. So trans vent tube should always face towards the front of the car?
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Old 06-17-2013, 05:38 PM
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Quote:
Originally Posted by voitureltd View Post
So trans vent tube should always face towards the front of the car?
For these gearboxes yes, if your mechanic learned the trade with aircooled Volkswagens (Beetles etc) then they will have it facing rearward as thats how it is orientated on those. There is a service booklet from Porsche on the gearbox that shows the exact angle - its not directly forward, rather at about 2 O'Clock (pointing towards the B-post area). I was amazed that such a detail could have a disasterous effect on the gearbox as I also had mine rebuilt due to no oil being in it when I purchased it and continuing to empty itself of oil until I turned the vent (thanks to a suggestion from a fellow Pelican).
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Old 06-18-2013, 05:02 AM
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Amazing! Thanks for the replies. I will check first thing this morning!

Hard to imagine that the wrong vent clocking could cause the transaxle to regurgitate its contents--especially without leaving oil tracks on the trans case.

I'll report back.
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Old 06-18-2013, 06:58 AM
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I just checked the car and found that the vent appears to be clocked correctly, pointing forward, slightly to the right of directly forward. No sign of any oil anywhere near the vent, on the top or sides of the bell housing.

So it appears that's not my problem, or at least that is not where the oil is exiting the trans.

Now what?
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70 914-6
Old 06-18-2013, 07:15 AM
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Amazing, totally amazing...
Old 06-18-2013, 07:16 AM
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Leaking out the shift shaft into the tunnel? Remove the cover on the tunnel behind the seats and have a look.
Old 06-18-2013, 07:23 AM
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Jim:

Good suggestion. I'll check that out. Are there weep holes there that would allow the oil to drip down and somehow get back to the engine?

Visual inspection shows no oil coming out anywhere forward of the trans.

I'm thinking of getting some fluorescent dye to put in the transaxle to help trace where the oil is going.
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63 904 (086), 63 904 (038)
70 914-6

Last edited by Telerding; 06-18-2013 at 09:06 AM..
Old 06-18-2013, 07:52 AM
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Hey Tom! Nothing to add, just wanted to say HEY! Hope you're enjoying the car. Still keeping it stock for concours or are you going to smarten up and make it 'right'? 8-)

Say, are you guys all using Swepco? Or Royal Purple?

I'm getting a nominal graunch into 4th until it's really warmed up, hoping a flush 'n fill will remedy.

How much I need, and source?
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| '07 S6 | '98 M3 vert | '01 M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 S8 | '95 S6 6gang | '88 M5 | '87 190E 2.3-16 |
Old 06-18-2013, 10:35 AM
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Ok, so looking at your first post, there was about 5 months between each check of fluid level in the gearbox. How much did you put in when you topped up? This will give us an approximation of the "leak rate"....

When you say there is an engine oil leak, have you noticed this as a drop in level on the dipstick in the oil tank over time? Have you had to top up the engine oil?

If you clean it all from the engine/pipes etc, check/top up gearbox and go for a drive, is the engine coated with the oil right after as you describe or how quickly do the engine cases /pipes get covered?

If the leak is slow enough it's also possible it may be exiting the gearbox from the input shaft seal into the bell housing. If the rate is very slow over the 5 month or so time frame it might not show up any problems with the clutch/pressure plate and may have an exit where the bell housing bolts to the crank cases and is finding its way along the cases assisted with the airflow under the car. Although, intuitively, if the leak was this slow it should probably not end up as wet oil on the engine and pipes as you describe, especially when the engine is hot from a drive....
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Old 06-18-2013, 01:54 PM
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Paulie: Say Hey! Yourself. Glad to see you are still trolling these environs on a regular basis. I still love the car, still stock as I can keep it. But a bigger turbo keeps calling to me!

I use royal purple. Amount is in the users manual. Can't remember how much.

CFD: good logical questions. I'll try to answer tomorrow.
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70 914-6
Old 06-18-2013, 09:59 PM
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Good to hear from you again Tom, and that you're diggin the car. How 'bout some pics... damn that color is just fiiiiiiiiiiiine!

*cough*headers*cough*intercooler

I'd skip bigger turbo and hit those items first - transforms the driving experience, really makes these cars RIGHT

just sayin 8-)

M5 runs Royal Purple, but I know some swear by Swepco for these. Coin toss I guess.

How's my Daytona? heh heh
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| '07 S6 | '98 M3 vert | '01 M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 S8 | '95 S6 6gang | '88 M5 | '87 190E 2.3-16 |
Old 06-19-2013, 05:42 AM
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Paul:

Daytona is just fine, considering its over 40 years old. A few battle scars, but runs fine. Just drove it down to Pasadena (360 mi. Round trip) for a car show a few weeks ago. Ran like a top, and got 15 mpg on the trip. Not bad for six two-throat Weber carburetors!

The problem of even thinking about modding the Porsche is where do you stop, AND HOW DO YOU STILL PASS SMOG HERE IN Calif**kyou? Besides, all that cough-ing could kill you!

Anyway, come out here on a visit and you can drive the Daytona.
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Old 06-19-2013, 06:52 AM
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Quote:
Originally Posted by Telerding View Post
Daytona is just fine, considering its over 40 years old. A few battle scars, but runs fine. Just drove it down to Pasadena (360 mi. Round trip) for a car show a few weeks ago. Ran like a top, and got 15 mpg on the trip. Not bad for six two-throat Weber carburetors!
NICE - good show, Watson! Keep up the good werk...

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The problem of even thinking about modding the Porsche is where do you stop, AND HOW DO YOU STILL PASS SMOG HERE IN Calif**kyou? Besides, all that cough-ing could kill you!
Califukkyou... HA!

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Anyway, come out here on a visit and you can drive the Daytona.
CAREFUL!!! 8-) I've driven a Lusso but a Daytona's fersure on ze bucket list. Only been to CA once so far regretably coupla years ago for a wedding... scared if I go again I won't leave! You've got a Berlinetta IIRC?
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past:

| '07 S6 | '98 M3 vert | '01 M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 S8 | '95 S6 6gang | '88 M5 | '87 190E 2.3-16 |
Old 06-19-2013, 07:09 AM
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CFD:

It looks like about 0.55 qt is disappearing every 1000 miles +/-.

I haven't noticed significant engine oil loss but I have added perhaps a quart or so in the last 2000 miles.

I now have a good reference point for both oil levels. I have cleaned off most of the oil residue on the underside of the car. Today I will take it for a 30 mile drive and then inspect the underside and report back.
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63 904 (086), 63 904 (038)
70 914-6
Old 06-19-2013, 10:49 AM
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Sounds good. Be interesting to see what you find. That's about half a liter, so certainly something not right there. Few thousand miles and your gearbox wont have much oil in it...mine takes about 3.7L...

Its also possible to do a crude check of the inside of the bell housing to determine if you do have oil in there from an input shaft seal failure - the photo below of mine shows the openings that you could get something in through - clean rag on a wire end etc - to see if it comes out oily.


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