280SL Automatic Tansmission - Audible Noise While Slowing Down

[nachum kadmiel]

Hi All,

Newbie here, so sorry if that has come up before - I searched and couldn't find....

I have a 69 280SL, and while slowing down, especially when the engine is warmer, I hear a strong knock when slowing down, when the gear shifts.

This happens sometimes when the gear shifts up between 2nd and 3rd.

Is this an adjustment problem, or is it something worse?

Thank you in advance,

Nachum

[Cees Klumper]

Welcome Nachum - I don't recall this coming up before, although 'harsh downshifts' is a common occurrende. Various possible causes come to mind, such as defective pressure switches on the transmission, 'frozen'/stuck solenoid that regulates internal pressure, and wiring issues. But with your description, I would also check the condition of the transmission mount. I think searching on each of these key words will get you a lot of information to use in your diagnosis. Good luck, and I am sure others with more knowledge will jump in soon.

[Pawel66]

Nachum, in the Technical Manual on tis forum you have quite a lot about how the solenoid Cees is mentioning should work and how to check it. There is also a description on how to adjust automatic transmission for it to shift smoothly. I would study it first.

You will find this material here: https://www.sl113.org/wiki/Automatic/Start

Then try to search the forum with the key words Cees mentioned. Indeed you will find all you need there.

Checking the gearbox suspension is easy with the car up.

If you do not know how long ago transmission fluid and filter were replaced - it is a good thing to do too.

Nobody can tell for sure, but what you are experiencing may be just a question of adjustment indeed.