Loudgoldwing

Two more interesting things I've discovered about my '98 Cabriolet:

1) The gas pedal depresses in 2 stages. The "light" stage is feathery soft down to about 30% pressed. Then, I can feel it encounter a more springy tension. It feels like the throttle body might be actuating a spring loaded intake plenum or something. But, that's also where it feels like the ponies kick in and the car accelerates quickly and confidently.

Which brings me to the transmission part:

2) When accelerating from a stop and only using the "light" area of the gas pedal, the tranny is just "disorganized." Sometimes it shifts early. Sometimes it shifts late. Sometimes it shifts just fine. The ODD part is, If I drive the car from stop and accelerate in the "springy," more tense part of the gas pedal, the heavier acceleration causes the tranny to find its "happy place" and it shifts smoothly, cleanly, and perfectly through the entire range. Seriously, if you're not looking at the tach, you can hardly tell it's shifting.

The Check Engine Light has never come on (except for when you first turn the key on, to prove that it has a bulb). However, I've heard that this wierd tranny behaviour could be one of the signs that a MAF sensor is on its way to car-part Heaven.

I know that the tranny on this model of vehicle is suspect, but I swapped out the fluid right after I got it and both the fluid and filter were used, but free of debris of any kind. It just doesn't make sense to me that a light foot on the accelerator gives a tranny (mild) fits, but a heavy foot makes it shift like butter. (And when I say butter, I mean ABSOLUTELY NO slipping, missing, clunking or ANYTHING. Just PERFECT!)

So, is it possible that what I'm feeling as the "first stage" of light-as-air gas pedal travel is a sign that something in the throttle body is loose or disconnected, thereby causing a conflict between the throttle position sensor and the transmission control computer? I've driven a vehicle with a bad transmission before, and being more agressive with the accelerator CERTAINLY didn't cure it of its issues like this does...

I really love this car. It challenges me to become a better owner. Kinda like a pissy, spoiled cat.

hubturn

First I would look at the throttle cable and see that all is moving smoothly. After that some research may be needed. Attached are a couple of pages from the Audi 4-Speed Automatic Transmission service training manual that I thought might help for big picture purposes. This is for the 097 transmission which you probably have, as I do on my Cab. I didn't know there was a separate vag-com port for this. Since it seems throttle related, I'd look at that throttle potentiometer.

Loudgoldwing

I don't have a "Sport Switch" I have to assume that the transmission in my vehicle is likely not the one you are showing me in the .pdf's

However, I understand the basic principle, totally "get" where you're coming from, and am EXTRAORDINARILY grateful for the diagrams. The give me a REALLY good starting point.

Let's see what the cable says first, and work from there... I think I remember it looking a little wierd (floating freely in the harness) when I yanked the Idle Control Valve to clean it. I had just chalked it up to an odd design, but now I'm not so sure...

I'll keep you posted. In the meantime, if anybody else has ideas, I'm all ears.

Thx, Sean

1993audi90

Hubturn: would you happen to have a document for the "final drive" part of the auto trans, specifically where the seals are and how to replace, where the fluid fill plug is, type of lube and amount? That's a lot to ask for, I know. I have a leak which seems to be coming from the flange the axles bolt to. I assume the axles are bolted to the final drive...

maineman

Right beside the axle on the drivers side there is a 17 mm internal hex head bolt. That is where your final drive fluid goes. I used Mobil one synthetic gear oil on mine.I don't believe there is a drain plug. At least I don't remember it.
Do you have a repair Manual?

1993audi90

No, I don't have the manual. If I switch to synthetic--which frankly sounds like a good idea--how do I drain the old? Pull the transmission?
Do you know how much fluid when full? Top of the drain plug hole?

maineman

When I put my used tranny in it didn't have fluid in it and yes you fill till it runs out the hole. I've read that people suck it out with different types of things .When the car was new it was supposed to be lifetime fluid ,that was part of the problem why these trannys are problematic.

hubturn

Loudgoldwing, I assumed that you have a USA model Cabriolet. They kept making them in Europe and some had a 1.8 turbo. Do you have the 2.8? I'm not at home and don't have access to my manuals. This training manual is a good overview, but not a teardown type document. I also have to reload my Bently's manual so someone else may have quicker access to 1993Audi90's request. Surely there is a serial number on the tranny to identify it. I just can't remember where it is located. Any help out there?

Loudgoldwing

Mine is a 1998 2.8L V6 4-speed automatic.

1993audi90

Apparently changing out the seals between the trans and final drive requires removal of the trans. Doing some searching, this failure is possible, allowing the gear oil and trans oil to intermix, but chances are if they do, the trans will likely need a rebuild anyway. If removing the final drive fill plug results in a stream of oil coming out (final drive waaaay overfull), or smelling gear oil on the trans dipstick are signs. I'm not sure I'm there yet. I've got serious leakage evident where the trans lines parallel the cradle between the engine and trans. Some of it is trans fluid, some is not. Could be PS fluid. Could be rear main in engine. Hell, it could be the oil seal under the intake leaking and rolling back and down. There appears to be a slip joint in the trans lines right there too, so perhaps that is a source. I've also heard the dipstick tube is sealed with an O ring that could fail as well. I'll take some pics Friday and post.