Automatic Gear Selection Problem

[DavidBrough]

Could anyone help me with a problem I have been having when selecting reverse gear in my 280 SL Auto. When engaging reverse, the engine revs rise momentarily by about 3/400 rpm just as the gear is selected then return to normal idle which is set at about 800 rpm. This causes the gear to select very harshly and requires quite hard brake pressure to keep the car stationery. Once selected everything is then OK. The idle solenoid is adjusted out of the way and the selection of forward gears is quite normal with only a slight initial drop in rpm and a steady return to normal tick over. I have had the car for about 2 years and it has always been the same so I thought it was time I did something about it. Does anyone have any ideas on how to fix it?

[Rocket]

David,

I had a similar problem which I solved by adjusting the venturi switch correctly on the inlet manifold. I obtained the information to do this on this site somewhere.

However there are two oil pressure switches one on each side of the gearbox. I think when you engage D or R the oil in the gearbox should pressurise either one which grounds and switches off the constant speed solenoid on top of the manifold and reduces the rpm. It could be the reverse pressure switch not activating the solenoid which would probably cause the car to engage in a harsh manner.

The answer probably lies somewhere here, but you need to do some testing.

Rocket

230SL 1965

[DavidBrough]

Thanks Rocket, I'll do some digging.