Overdrive going out

[werkenklasse]

Hey Guys,
Got a 2001 F350 CC,Auto, LWB, 4x4 Lariat with 192k miles. I had a rebuilt transmission and triple disc torque converter put in at 170k miles. Two weeks ago the overdrive began to act strange- would kick in in then kick off for a minute or two before kicking in for good on the highway. Now the OD seems to be slipping and the truck wants to stay out of OD altogether.
I just had the trans serviced under warranty two months ago. I am not sure what the problem is. Any suggestions?

[Codum]

Do you ever find out what was wrong? I think mine is kinda doing the same thing.

[werkenklasse]

I did. Took it into the shop and they opened up the transmission and discovered that the acumulator valve for the overdrive was sticking. The spring was flattening out. He replaced the magnesium valve with a steel one ( supposed to prevent sticking ) and put it all back together. It runs fine now with no problem. The head mechanic did say never to put Lucas in the transmission fluid. It rusts out the valves.