Problems changing gears when cold...

I have an 01 discovery, in the summer it changes gears no prob, in the winter it will not change into top gear(even if warmed up) till maybe 4 miles of driving then it clicks over...  Any suggestions, land rover ran a diagnostic and came up fine..

I replaced most of the fluids, transmission and transfer case not long ago..  didnt fix the problem

How many miles on your tranny?
If it doesn't lock up till around 50 t0 52MPH, that is normal especially when cold, the ECU holds it back to allow the engine to warm up quicker.

about 118,000, no this def not normal, i have to drive about 50 mph and riding 3rd gear at about 3,000 rpm, for figure 10 minutes...   cant really jump on highway's cause im limited to 50 55mph with the motor reving out, which is not good...  I think this reving out caused me to blow the headgasket...   next step it going to blow the motor, so i have to fiugure this out or get rid of it...
 
it shift fine in the summer and fine in all bottom 3 gears just wont go into 4th unless the oil is warm in the tranny i guess because leaving the car to warm for an hour in the driveway wont make a diffrence, still doesnt change, has to be driven.. 
 
I'm out of ideas

So, try a bottle of Lucas tranny additive just in case you have a valve body hanging up, this may correct it.
If there were a problem, either the ECU or the tranny control unit should throw a code.
Worse case, go by a tranny shop and have them plug in and drive it after it sits all night. If there is a problem their scanner will see it in real time.

thanks mike, ill try the additive and then try a tranny shop, figured i'd check here if this was a common rover problem..