Done all the reading and research here that I can, now I need to ask.
Bought this 81 380SLC that had already been worked on or over by its previous owner, including a transmission rebuild.
One of the last things he had done was replace the modulator, trying to fix a engine smoke problem. I studied the posts, assembled the gauge and in park and @ idle, have little to no pressure @ modulator port and governor port, have decent pressure @ the operating pressure port 40- 50 psi(on passenger side of tranny.
Here is the main problem, I can live with the shifts flaring and softness, can adjust them somewhat with the bowden cable and the modulator setting-
but... once underway and into 4th if I let off the speed, it loses the gear and goes into neutral, I then have to slow down to below 10mph to start out in 2nd again. Any help will be appreciated. Hate to part her out, just got the smoking engine issue fixed.

Sounds like the trans doesn't have enough pressure to keep the 4th gear clutch pack locked-up.

Either a valve body issue OR worn seals at that clutch pack.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator