it happens every six months

[bill threlkel]

This is a strange thing i will be driving a long and the trasmission will start to slip like it was not in gear. I pull over to the side of the road stop put car in reverce then drive then its ok for 6 months. This has happened twice this year. Is there any electrical conections in the ****ing lever? Ichecked the vacume lines they are in good condition. Just hope it will continue to fix its self i guess. Any body have any ideas? The car is 1983 300sd
Bill

[BobK]

Two ideas:
Maybe a bit of dirt is blocking something in the valve body and dropping presure to a clutch. Have you flushed the tranmission recently?
Other idea: worn motor/transmission mounts moving the tranmission enough that the lever is no longer in the gear you think it is?

[bill threlkel]

Bobk
Changed to amsoil in trans. about 25000 ago so going to change oil and filter and check mounts.
Thanks Bill

[Ken300D]

It does sound like a sticking piston in the valve body, particularly if this happens during a gear change.

Had the same thing going on in the 1982 300D at the 3-4 gear change in cold weather. Switched to synthetc ATF and problem was quickly resolved. Synth has better cold weather characteristics and also is a good cleaner.

Much cheaper than a trans overhaul.

Ken240/300D(SD)

[jbaj007]

Since you are going to change filter and tran fluid and perhaps mount(s), check the linkage bushing also, just for kicks while you're under there.