Trasnmission fluid in engine oil

I have a 91 pontiac Grand Prix with a 3.1 and the car has NO leaks, however, I have noticed that the transmission fluid level go down and the engine oil goes up. My conclussion is that some how the tranny fluid is crossing over to the engine, is this posisble? and if it is, how or where? NOTE: my car has a tranny cooling line to the radiator but no engine oil cooling lines and the colant is clean. how is it posible? Please, somebody help me out!!

additional comment: the oil smells go, I loose 4 qt of tranny fluid and gain 4 qt of engine oil.

It can happen by somebody running a vacuum line from the crankcase to the transmission modulator valve which has a broken diaphragm. Better check hose routing even though I don’t know if there is a small line that can be connected in such a way. Sure sounds good.

Disconnect the vacuum line from the PCV valve. You will likely find ATF dripping from the hose. @pdv is most likely correct. The modulator valve is bad… Does the engine seem to rev too high before shifting?

pleasedodgevan2… I’ll check for a vaccum line of some kind and will check the tranny mod valve for broken diaphragm.
rod knox…this model don’t have a PCV… the vent hose goes straight from the valve cover to the throttle body and the engine runs smooth, no misses, over idle or nothing. I noticed that as the crankcase gets full, it smokes (from over filling), other than that everything else is fine.
GUYS…please stay tune… I will check it today will repost later. thanks.

Most engines have PCV valves these days although some imports use a fixed orifice. Your 3.1L has the PCV under the throttle body I believe. And to some of us the problem of ATF migrating to the crankcase is not new.

Please post the results of your investigation.

The problem has moved four QUARTS of oil from the transmission to the engine? You may now have lather problems. The engine would be severely overfilled and the transmission severely under filled. How long was it driven in this condition?

ding, ding ding… we have a winner…PLEASEDODGEVAN2, what you said made sense so I checked the modulator, and sure enough, it had fluid on the vacuum side of it. Replaced the modulator valve, the engine oil, filter and added tranny fluid. everything is ok, for now, it used to do this like every two weeks, so will see, but I am sure that that fixed the problem. Newer cars like 93 and 94 have an “air only” valve on the vacuum side of the valve, to prevent just that, too bad nobody passed the info from the factory. By the way, I got an “air only” valve from a 93 and went ahead and installed on mine, works just fine.

roc knox… this engine, the 91, 3.1 does not have a PCV, I had found it when I re-built the engine and the book also saids that there isn’t one.

macfisto… the engine and all the other components are ok… I provably have the cleanest engine around though, (cause all the tranny fluid in the engine).

Thank you guys, great help, and may I be the one that help you next time, Again, Thank you all.

If it doesn’t have a PCV valve, then what does it use to make sure the crankcase pressures stay negative rather than positive?

@Palomo according to rockauto, this is the PCV valve for the 1991 Grand Prix 3.1

Where is yours?

We are all happy that you found and corrected the problem before you had a catastrophic failure in a snow storm on your way to the maternity ward, @Palomo. Pleasedodgevan gets 1 point added to his score. When he reaches 1 million points he gets a 10% discount on a free tire rotation.

I could use a bargain now and then. I may be old but I make up for it by being slow too.