It sounds to me like your transmission is on the way out. It is very hard to find anyone to actually fix transmissions because you are looking at 9 hours labor to take it out and put it back in. So you are in it $850 or so to start. Then more often than not, a repair on the "whatever" is made to fix the shifting problem say $300, and it goes back in the car with a new filter and fluid ($100). So the bill is $1250, and 2 weeks later the trans starts to slip, or won't go into 4th or whatever, and the customer comes back mad.

So most shops recommend a rebuilt unit which comes with a warranty when problems like this occur.

I personally wasted $200 on a service with synthetic fluid, then another $250 on a pressure check and adjustment, and $200 on a rebuilt valve body in my disastrous 1981 380's trans. The thing never worked right, and I wasted the money that could have gone toward a $1500 rebuilt trans.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe