I have a 1984 300SD that is shifting weird. It seems to shift ok when it's cold, but when it gets warmed up it seems to shift into 4th gear too early. It shifts almost straight from 2nd to 4th, spending 1/2 second or so in 3rd. And I can see the revs go way up on the tachometer in between, like it stays out of gear too long. If I use the shifter to force it to stay in 3rd, and then go to "drive" when I want 4th gear, it shifts beautifully.
I just bought the car from a used car dealer and had to take it back the next day to get a big oil leak fixed. It was shifting fine before they fixed the oil leak, and then when I got it back the shifting problem started.
When I check the transmission fluid, there are bubbles in it. Any ideas what causes these bubbles, whether they're related to the shifting problem, and how to fix it?