slow shifting into 4th when cold
 

1986 190 with auto 386 000 km / 240 000 miles. All other shifts fine, when I first set off, (below freezing here) I get one heck of a slow shift into 4th. Not so bad when hot. oil level fine, color good, allison transynd synthetic oil (already in the car when I bought it) I have never serviced the trans since I owned it (8 months)

Does it flare or just not shift up till higher rpm
 

Slow up shift when cold sounds like something is leaking or sticking in the circuit from the K2 piston (valve) to the K2 clutch, usually this occurs when the trans is hot. Depends on whether you are flareing on not. The Superior Shift Kit thread might be of help. You could try turning up the modulator pressure a bit to see if that helps. It is the small unit on the driver side of the trans to which the vacuum hose attaches, pull off rubber cap and pull out the little T handle 1mm or so till it clears the notches then rotate clockwise not more than 1/2 to 1 turn. This will also harden up all shifts so use care. Cheers Dan