1984 300SD, Auto Trans. I need help.

[Lampbum2]

Hi,
I am having a problem with the trans. slipping..... today I was at a light and pushed down hard on the throttle....it started to go and then it was like it went into neutral.....the motor RPM's just took off into a high rev. until I let off..... then it was fine.
It also does it when I am turning from a stop sign and I floor it.......Any ideas?

The filter and fluid is fresh and at the full mark, changed about 3,000 miles ago, just put a new K-1 Spring in.....second to third is great now.

New motor mounts and oil lines....

Thanks ahead of time for your help!!!
Jim