3 days ago my 1994 Volvo 940 Wagon abruptly started having odd shifting behavior which it's never done before in the 10 years I've owned it. The car will not shift gears while accelerating -- it will reach very very high RPM's -- until I remove my foot from the accelerator. The only exception to this is that the car does switch from 1-2 (i.e. the first two gears when accelerating) while my foot is on the accelerator; however, even this shift is coming late, and the revs are getting much higher than normal. So my experience accelerating onto the highway, for example, is like this: begin accelerating, and the car makes a high-rpm and rough transition from 1-2; keep accelerating and at about 35 miles per hour the car is at very high RPMs and not shifting, so I remove my foot from the accelerator. After about a second the car shifts from 2-3. Continue accelerating to about 55, at which point the car is once again at very high RPM's and showing no sign of shifting. Again, I remove my foot from the accelerator, and then the car shifts from 3-4 on its own. Any ideas what could be causing this? I haven't had the fluids checked/changed in about 7 months (about 2000 miles driven since last oil change). It does have a slow oil leak, but I keep it topped off myself between oil changes every 3000 miles, so there shouldn't be any problem there.