There were 3 different automatic transmissions for our R129 (and there used to be manual transmission too).
The 'early' 300SL had a choice of 4-sp or 5-sp hydraulically controlled Automatic (as well as the manual transmission) while the 500SL had only the 4-sp because that 5-sp could not handle the power/torque of the big V8. Both of those Automatics starts with 2nd gear, but will downshift to first when punched.
Later (I think it started with model year 1996 ?) the electronically controlled 5-sp was introduced which starts in first gear and has winter driving mode etc. It was also 45 lbs lighter than the earlier 5-sp, and with locking torque converter, it got better MPG too.
Can your 1990 500SL be upgraded to the later 5-sp ?
While anything is possible, it will be very expensive as the Electronic Transmission Control module has to "talk" to the rest of the various controllers of the car, which your earlier SL does not have.
The 'early' 300SL had a choice of 4-sp or 5-sp hydraulically controlled Automatic (as well as the manual transmission) while the 500SL had only the 4-sp because that 5-sp could not handle the power/torque of the big V8. Both of those Automatics starts with 2nd gear, but will downshift to first when punched.
Later (I think it started with model year 1996 ?) the electronically controlled 5-sp was introduced which starts in first gear and has winter driving mode etc. It was also 45 lbs lighter than the earlier 5-sp, and with locking torque converter, it got better MPG too.
Can your 1990 500SL be upgraded to the later 5-sp ?
While anything is possible, it will be very expensive as the Electronic Transmission Control module has to "talk" to the rest of the various controllers of the car, which your earlier SL does not have.
