230SL automatic transmission randomly slips into neutral - not touching shifter

[kewaskum]

Hi,

I have owned a 1967 230SL (automatic) for ~25 years now and it just did something new on my normal Sunday morning drive. 

On the highway, I was going ~80 MPH and the engine suddenly revved up as the automatic transmission appeared to slip into neutral.  I was not touching the gear shift.  I backed off the gas and it ran normally again.

2 miles later, it did it again at ~30 MPH.  It is in the shop and my mechanic reports that the linkage (and little grommets that fail so often) are fine. 

Any ideas on what this could be are welcome as it is one of those "not always failing" issues that can be frustrating to diagnose.

thanks,

Tom

[Cees Klumper]

Silly question perhaps, but is the fluid level ok?

[kewaskum]

Thanks for the question. 
It was checked and is fine.

[Benz Dr.]

I would look at shifter bushings.

[kewaskum]

I think you are referring to the little rubbery things I called "grommets" that periodically dry out and fail.
If so, those were checked and were in good condition. 

side note - I have been stranded twice when those let loose as the shifter becomes totally disconnected from the transmission.  I try to get them changed every 5 years or so to avoid that.

[Ed Riefstahl]

Hi Tom,

My suggestion would be to call Mark at Sun Valley Mercedes Transmissions. As some on this forum know, a year ago August the transmission on my 230SL did some very strange shifting and shifted so hard a couple times that is took the differential out. It actually snapped the shaft on the slip joint / yoke.

Mark was very helpful and spent considerable time on the phone with me explaining the torque converter (he had a different name for it) problems with the early SLs.

It doesn't sound like linkage / bushing issue to me, unless you can feel the play / slop in your shiftier. Just my 2 cents.

Ed Riefstahl
Erie, PA

1966 230SL (Ms Magoo)
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - Red 5 speed (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5

[kewaskum]

Thanks for the reference, Ed.

My 1969 Chevelle is easier to keep on the road, but not as fun to drive 

[kewaskum]

Hi,

I wanted to update folks reading this thread (even if a bit embarrassing for me)   
The trans fluid level was re-checked and found to be a bit over a pint low.  (!!)
Test drives since addressing that have not shown the issue so I am hoping that "easy fix" is all that is needed.
I really appreciate the help and tips provided here.

thanks

Tom

[rwmastel]

Thanks for closing the loop.  Helps in the future when other people with the same symptoms are searching threads for help.

[Benz Dr.]

Something to note.

The amount of fluid to fill from the bottom line to the full line is not a liter like what we would find on our engine dip stick. Transmission dip stick is more like 300 ml. Don't over fill your transmission.

[MartinK]

Maybe the idle switch which is located at the throttle is dead or disadjusted. If it is closed while cruising, the modulation pressure drops down and maybe the transmission slips. Just my Idea. Talk soon, Martin

[rwmastel]

Maybe the idle switch which is located at the throttle is dead or disadjusted. If it is closed while cruising, the modulation pressure drops down and maybe the transmission slips. Just my Idea. Talk soon, Martin

The trans fluid level was re-checked and found to be a bit over a pint low.  (!!)

Martin,  He found his problem a few posts earlier.