Tranny can't find gear.

Hi everybody, board newbie here with a question.

My SVX has 125k on original tranny, so I figure I've been luckier than many. However with in the last month or so it started really searching for gears in drive . At road-speed(35-40) it constantly jumps between 2 and 3. and at highway-speed(50-65) constantly jumps between 3 and H. by constantly I mean a shift every 2 seconds or so.

Unfortunately I'm not in a financial position to get a tranny fix right now, I'm hoping to drag the car along another three months while saving some cash.

I can also manually undergear the car by putting it in 2 or 3, which forces the lower gear to run, and stops the shifting, but makes it run consistantly over 3500 RPM.

But I'm wondering if the increased RPM speed might be making extra heat, and causing more problems than the shifting does. Is either preferable, is either hurting my engine more(my enigine is perfect still, and I'm hoping it will stay that way until I get the cash to get the tranny fixed). Which is more likely to get me my 3 months driving 25 miles to work every day.

thanks,