1988 560SL Transmission Q's

Hi Folks,

I'm back, this time with a question about my dad's newly-acquired 1988 560SL. Just a quick bit of background here - I am an ASE/Toyota Certified Technician. I know about Toyota transmissions and NOTHING about Mercedes-Benz automatics

Anyways, my dad called me up today and told me that:

1) His ATF level did not register on the dipstick when checked according to the owner's manual. He was prompted to check the fluid due to the following symptom:

2) Intermittent lack of upshift from 1st gear to 2nd gear.

This only occurs when cold, but not immediately. This will happen after driving several blocks and after normal upshifting.

The symptoms do not occur in the afternoon after the car has sat all day long, only after a cold soak period and after driving a few blocks.

Do these transmissions use a vacuum modulator?

Is this an electrical/solenoid problem?

Is this something I can repair with the transmission still in the vehicle?

From my Toy. experience I'm guessing that it is either an electrical fault or vacuum related.

Any input is greatly appreciated.

Thanks!

- Jim