I have a 91 svx with 136,000km and transmission was serviced about 25,000km ago. Last week the transmission developed a fault. When accelerating from standing in D the transmission slips extremely badly. On partial throttle it will redline while travelling at about 5k's. If you take off really slowly you can feel it partially grippingenough to accelerate, this lasts until there is enough speed to shift into 2nd after which there is no problem. Downshifts to 1 also cause the same problem. The interesting factor is that if you put the car in 1 there is no problem. In 2 and 3 and in Manual Mode the car has the same problem. I have checked all the error codes but there aren't any.

Any ideas would be Great
Thanks