losing tranny fluid, but where? + noises!

My '97 is driving me nuts, and I was already most of the way there. I keep losing tranny fluid, but there's absolutely no evidence of leakage below the car on the driveway.

I added fluid about 1 1/2 months ago, when the tranny was making strange noises - like a whooshing sound. The tranny never acted up, never slipped, nothing - but the thing was making a weird noise. When I checked the fluid, it was way down, even though I had checked it not long before that. I put in TWO quarts, and the noise disappeared.

The other day my wife said the car was making strange noises. This time the noise was worse, more like a rattling sound. I couldn't believe it could be the tranny, but after checking the fluid it was down again - over 2 quarts again. When I added fluid the noise quieted, but not completely. Again the tranny never slipped or acted erratic when the fluid was low.

I'm at a loss to understand where the fluid is going. Also at a loss as to what causes the noise when the fluid is low. I'm afraid the tranny is going, but it acts perfectly fine - if you don't consider the weird noises. I want to save the tranny, but I'm not sure where to start.

First thought is into the radiator, but if your coolant is staying pretty even then it shouldn't be there. Not four quarts worth anyhow. I've never seen a transmission 'eat' up fluid before, so I don't *think* it'd be that. That's the only lead I have for you unfortunately. There's lots of good people here though, and pretty much all of them will try to help you out. Hang tight!

The only thing I can think of is to check the seal under the speedometer sending unit. Its a black box with a 3? wire connector on the backside of the transmission. I dont see how it would leak out ThAT much but I suppose its possible. Worth a shot at least.

That is a mystery!! On the older ones., they had a vacuum modulator that was plumbed to the intake manifold of the motor, and when the diaphragm went bad, it would suck fluid out and into the engine, resulting in smoking exhaust and slipping shifts. But that isn't the case here. You are not the first to describe that particular sound on one of these before the tranny went bad. Did you have it serviced, and is it possible they shortchanged you on fluid? Maybe it never had enough to begin with. When I serviced mine, I noticed that it did shift perfectly, despite being over two quarts low. I had to drive it 1/2 mile to get more fluid. Are you sure your dipstick tube is fully seated in the tranny? That can give incorrect readings of fluid level. I wish I could tell you more....

check the hose that connects to your vacume modulator if there's fluid in it then it's getting sucked into the engine itself and burned and exausted (you would definetly notice a cloud behind your car when you drive it)

only some of the 97's had a vacuum modulator(most were electronically shifted), but if your's has one, that's where your fluid is going. They can draw a small enough amount that you'll never see smoke, but like Ken said, the vacuum hose leading to it would have oily residue in it if that's where it's going.

Thanks for all the great info. I took the advice on the vacuum modulator - mine has one - and changed that. This seems to have stopped the loss of fluid. What's interesting is that there was a slight amount of fluid in the vacuum hose by the intake manifold, but no great amounts were obvious - just a slight residue.

The modulator itself - according to the manual - could be rotated and if the fluid leaked out of the hose ending, this would indicate a bad diaphragm. When I did that nothing came out. After I took the old modulator out, there was hardly any evidence of leakage in the body of the modulator. But since changing it about 2 weeks ago, the fluid in the tranny has remained unchanged.

Someone mentioned smoke in the exhaust. This had happened prior to changing the modulator too, but only on start-up. There were puffs of smoke only when starting - not running. Had I been more experienced with the modulator problem I probably would have known the telltale signs. But this was the first time I ever had to change one.

If it hadn't been for the great advice here, I'm not sure what I would have done. I'd probably still be feeding fluid into the Lumina. Thanks!!

That was my first guess, but mine ('97) doesn't have one, so I figured yours didn't either. I thought they did away with those around '93 or so. My bad.

Jeff,
No problem. I appreciate the job you do as moderator here! You don't have to know the answer for every problem. That's why they have forums. Keep up the good work.

glad our advice helped you out, and it's rare that Jeff misses one, he's a good source of info.