auto transmission problem

[rwaw]

Dear group,

First of all congratulations on a brilliant source of knowledge; have only had my 280SL (1969) for 2 months but have used many of your tips already.
My immediate query is this: when driving off first thing (in "4")the auto box takes an awfully long time (i.e. high revs) to change up and when it does the revs shoot up to about 5000.
Fortunately this lasts for only the first 5 minutes or so till the engine is warmed up enough.
Any suggestions ?

Thanks for your help so far; I'm afraid I'm confused now:
When I check the fluid level as described in the handbook, i.e. with warm engine and engine running, the dipstick is dry.
However with the engine turned off, the level is always +/- 1cm above the highest mark.
Any help very much appreciated.

[Cees Klumper]

I assume you checked the fluid level following the owners' manual procedure.
This behaviour must be very unpleasant and is definitely not the way the car is supposed to shift. My own '69 280 SL shift points are very responsive to the gas pedal: when I want it to shift at low RPM's I go light on the gas pedal and, voila. When I want to pull to redline, I just press down (without engaging the kickdown switch) and there it goes. No difference between cold and warm engine in the shifting characteristics either.
There are various factors that, beside the condition of the transmission unit itself, come into play. Two of these: (1) the transmission linkage and (2) a 3-position switch mounted on the transmission that can be observed through a plate that is on the transmission tunnel on the passenger side. Joe Alexander contributed the following diagnostic procedure. You might want to start there to diagnose your problem:

"You can remove the access cover on the passenger side tunnel area and observe the movement of the transmission linkage and three position solenoid, while test driving the car. You will need a second person and a flashlight. The kickdown or passing gear switch on the floor under the accelerator pedal must be engaged and working to activate the solenoid. When fully depressed this switch is engaged and it energizes the three position solenoid which will move the control pressure linkage on the side of the transmission. This linkage changes the control pressure at the modulator assembly on the transmission and causes the downshift. Make sure you have power going in and out of the accelerator kickdown switch when it is depressed.

Next try observing the operation of the three position solenoid. Position one at idle in gear, position two after driving off, position three at full throttle (accelerator fully depressed and switch engaged). If all seems to be working ok then more complicated adjustments can be made at the modulator or the linkage on the transmission (do this only as last resort and after everything else is checked out).

Good luck, and please others (Bob, Tom, Joe) jump in if you recognize this particular problem

Cees

white 1969 280 SL

[ja17]

Hello rwaw, It sounds like you are telling us that the automatic slips when cold until it warms up. The first thing I would do is change the fluid and filter. You will need a new cork gasket for the pan with the filter. Make sure you drain the converter also since most of the fluid is in there. Possibly someone has put the incorrect fluid in your automatic.  When the pan is off examine it for parts or excessive sediments. Some particles are normal. While the pan is off retorque the small 10mm? possibly 11mm bolts holding the valve body in place. Often times they loosen causing a internal pressure leak and shift problems. When re-filling the transmission add about five quarts of fluid then start the engine and move the selector through the gears and fluid will be pumped into the converter. Finish filling, the car must be running, warm and on very level ground for a correct reading. The amount of fluid between marks on the stick is 1/2 quart! do not overfill. Test drive and re-check the level. If you overfill the fluid can be carefully drained off by loosening the transmission oil cooler line going into the radiator while the car is running. Check back if you need clarification or more information. Keep us informed!


Joe Alexander
Blacklick, Ohio

[Cees Klumper]

The fluid level should only be checked as indicated in the manual and as stated by Joe Alexander, with the engine running and at operating temperature, on a level surface. If the dipstick is dry then, you simply have too little fluid in the transmission. Try filling up to where it should be, and see if that alleviates your problem.

white 1969 280 SL

[rwaw]

Added 300mls "Wynn's auto gearbox protector" and problem solved. Car shifts beautifully and also position "P" now holds the car on gradients when parked !
Thanks for your help.