Lower Trans cooler line, ....
 

...not the spring wound ones at the radiator.
My lower trans cooler line from the tranny to the flex connector has had a leak in it(fixed by PO with some sort of amazing fix it putty as sold on TV by Billy Mays ).
I need to change this line out and need the part no.
Or I need this line. It's in my 1983 300SD.
It isn't leaking(wonders of wonders) but it needs to be changed out ASAP.

On my 300D it was a dealer part, it took about a week and cost around $100. I did the hillbilly fix of cutting out the leaking tubing and patching it with some fuel line until the correct part arrived. Just go to the dealer, also order the little grommets for the clamps.

We just tried to get one recently....there is one left in the world, and they want $132 for it.....the dealer gave us a shop that can make them.

We had two custom made using the fittings from the old tubes for about $115 for both....and they did an excellent job. I'd just take it to a shop and have it re-made if I was you....most tubing shops can do it in like 1-2 days or less....our shop did it in a few hours.