Automatic gearbox. Have I bought a pup?

[MrBunter]

Have just bought a 1967 250sl with four speed auto and I know that there are lots of posts about the "quirks" of the gearbox.
However, this one drops out of gear into neutral when I slow down at junctions/roundabouts when position 4 is selected (ie normal driving). Not a good situation. Knocking the gearbox into 3 immediately gets the car moving.
Also, the engine runs at 3500rpm at 60 miles per hour.
Any advice on these or have I bought a pup?
Many thanks

[Shvegel]

The high RPM's are pretty much normal. It takes some getting used to.  Dropping "into neutral" isn't normal. Mounted on the top of your transmission is a 3 position solenoid.  It changes the control pressure in the transmission and is supposed to change to control pressure at idle(low pressure),  normal, (medium pressure) and full throttle(high pressure).  I suspect the linkage on this may have frozen.  It can be accessed by peeling up the carpet on the right side(seated looking forward perspective) of the transmission tunnel under a sort of oval cover.  check it for movement and if it is free then search "3 position solenoid" here and you will find a wealth of information on the control system.

Here is a picture of the access hole from the underside:

[MrBunter]

Thanks Shvegel, I'll have a go at that. Incidentally, a lot of the electrics are not working( radio, electric aerial, heater fan etc). Is there any chance that power to the solenoid could be missing which might cause the problem of dropping into neutral?

[Larry & Norma]

Sounds like you should check your fuses, they can make a bad contact so even if they look good
give them a bit of a twist to help make contact.
Could also be a loss of an earth somewhere...

[Benz Dr.]

You might want to check that your trans is going into gear properly. Maybe worn shifter bushings or out of adjustment.