I've just bought a 1987 300SDL with 100k miles on it (one owner). The car accelerated well with no neck-snapping on gear changes. I'm new to M-B and automatic transmissions.

I changed the transmission oil (no burnt stuff or residue in the pan), and noticed that there was a transmission leak from the front of the transmission (in front of the torque converter, I suppose). The car now accelerates slowly, but does get up to a cruise of 75mph. If I press hard on the accelerator at about 40mph, the engine revs increase immediately from about 2000rpm to over 3000rpm, but the car does not respond.

Two questions:

1) How easy is it to replace whatever oil seal needs replacing to fix the leak?
2) Is something in the transmission slipping and is this a trip to a transmission shop?

 

you need to pull out the transmission to fix the leak.

have a check on transmission slip first. check pressures, vacuum and linkage.