Probably been answered before, but anyhow . . . . .

Autobox (240,000 km) won't pick up 4th when cold, needs at least 1 km of keeping it in 3rd before O/D works, otherwise it just free revs.

Put my foot down in 4th yesterday, the box changed down to second, then when I lifted it picked up third, but free revved again. Didn't pick up fourth until the engine revs dropped right down.

I suspect 4th gear clutch pack is rooted, how much are the parts and is it a DIY job?

there is a special seal its tricky not to damage it when fitting the new one

you can get the kit and diy

but its not a long job for an automatic repairer to do the box stays in
its just a cover to undo

something like $200-300 approx ... get several quotes

it is mentioned in the repair manual

Thanks for that info.

I will study it in the manual, didn't know it was in there.

similar set up in pictures and diy

http://www.mirage-performance.com/sonata/Transmission/endclutch.html

Thanks for the link. Very informative.

Looks possible to do, but I'd probably stuff it up. lol

I will leave it for now, if (when) it gets worse I will check out prices of the bits, and get quotes on getting it done.