'69 280SL missing shifts when cold

[johnshenry]

I have a '69 280SL that has begun missing shifts when it is cold.   As soon as I drive down the driveway, it usually miss the 2-3 shift and the engine RPM shoots up, and it usually pops back into 2nd.  It will do this for the first 2-5 mins or so it seems.  ATF level is fine.  Any suggestions on what to look for?  I am a vintage VW guy and have plenty of grease under my fingernails, but I have not spent much time under this Benz since I bought it.  I would think it might be a vacuum related thing?

So far no snow in New England, I can still get it in my shop to check it out and get this fixed before spring.

TIA for any help .....

[ja17]

Hello,

Sometimes the valve body attachment bolts become loose over the years allowing an internal gasket to leak. I would plan on a fluid and filter change and while the trans oil pan is off re-torque all the 10mm valve body bolts back to spec.  You will see the bolts plainly when the trans filter and pan is off. Use a new cork gasket on the transmission pan seal when you are finished.  Good luck, Keep us up to date.

Joe Alexander
Blacklick, Ohio