Automatic Transmission woes

[Sven]

All,

Finally got the car on the road after two years of tinkering.  Until yesterday, the AT would start in 2nd and shift at between 3,000-3,500 rpms.  Yesterday, the car began starting in 1st and needed higher revs to change (3500 rpm 1-2, 2-3, and over 4000rpm for 3-4).  Additionally, has a new tendancy to downshift from 4 to 3 just after upshifting if I don't remain constant on the throttle.  What gives?  Also at the same time (perhaps coincidental), idle went from around 1,000-1,200 to about 2,000 rpm.  Any thoughts (AT pressure regulator, kickdown (whatever that is), silenoid)?

1968 280SL

[Cortez-Campos]

I had the same problem last year, it shifted from 4 to 3 just after upshift, it was because the transmission oil was to low, so I went for a long drive so the oil was hot, then I refulled, and no problems.

280 SL 1969 anthracite 172, with red inteior.

[ja17]

Hello Sven,

Lots of things to check, as Cortez mentions, start with the fluid level first. the car must be running, warmed up and be on level ground.

Remove the side plate on the transmission tunnel (inside car) and make sure the three position solenoid is moving the linkage.

If the modulator diaphragm is broken, red automatic transmission fluid will be in the intake manifold and will be fouling spark plug #6.
 You may also notice white smoke from the exhaust.

Joe Alexander
Blacklick, Ohio

[TheEngineer]

Is your accelerator pedal hanging up? Tranny will only shift properly when idle speed is below about 800 RPM. Maybe kickdown switch is hanging up in the closed position?

[graphic66]

Check the operation of the double acting solonoid located on top of the tranny. This site has some good advice on checking the solonoid http://www.mercedesdismantlers.com/16BoltInstallationInstructions.html