My mother owns a 1996 Olds Eighty-Eight that has developed a magical ability plus another problem that multiple mechanics have failed to solve.
Magic: The car, a few miles after an oil change and verifying the correct amount of oil was put in at the change, magically generates more oil to the point the level on the stick doubles.
Problem: At the same time, the car has significant loss of transmission fluid, but no leak large enough to account for the loss.
I suspect the two are linked, and one mechanic even said that there was a valve or something that could go bad or get stuck and allow the transmission fluid to get pulled into the oil, but no one has been able to definitively reach an answer or fix the issue. Any help would be appreciated.
The two ARE linked. A gain of fluid in one part and a loss of fluid in another means a fluid transfer is occurring. This is due to an INTERNAL leak, one that is happening within the engine or transmission, allowing the fluids to move from one to the other. Since the transmission is losing fluid, and the engine is gaining fluid, the transmission is pumping fluid into the engine through this internal leak. The trick now is finding that leak.
Back in the day (pre-1980’s), this was typical of a bad vacuum modulator on the transmission, leaking trans fluid to the engine through the vacuum line. Since the mid-80’s, these modulators were removed as transmissions began to use the TV cable, then later were controlled directly by the ECM and TCM.
So, where to look? The external transmission cooling lines need to be inspected, especially if the transmission cooler is integrated with an engine cooler, maybe even together in the radiator for combined cooling. The transmission pump can pump up to 300 psi, while the oil pressure is typically regulated to about 80 psi max. That means a mutual leak will allow trans fluid to push into the engine oil.
The torque converter also holds a great deal of fluid, but has no direct connection to the engine block and oil. There is a large solid steel dowel that keeps the torque converter centered to the crankshaft, and that is the closest the trans fluid should get to getting into the engine.
Other than that, I’m at a loss. There is no other connection or interaction between the engine oil and trans fluid, and the engine case with oil in it is separated from the transmission case and transmission fluid in it by a bell-housing, unless the FWD transaxle arrangement is slightly different.
I’m not certain about it but its probably a 4T60-E transmission and if so then I believe that does actually have a vacuum modulator. (They were used up through about '98 or so on these GM transmissions). Whether the design is one that can transfer the fluid I don’t know. But its the first thing I’d look at.
The vacuum modulator is at least easy to check for rupture, and generally not hard or expensive to replace.