1999 Toyota 4Runner Sometime when you place in drive, moves

Thats where I would start be aware that sometimes if you add a adtive to clean you may cause more problems so take it to someone who can flush the system out but make sure to tell them the problem first and check with more than one quote="graygo"]Transmission problem
1999 Toyota 4Runner 6 cyl Two Wheel Drive Automatic 123000 miles

Sometime when you place truck in drive, moves like it trying to move in 3rd gear. Pull down to Low gear moves fine and may not happen again for awhile. Will servicing and replace fluid and filter do anything,
because its my son's car and I don't know how long its been since servicing.[/quote]

Thanks Ms Sherbert for your reply.

After placing this post, I went to a local transmission repair shop, and after they removal and inspection the transmission, they said the Torque Convertor needed replacing and based on the burned fluid the system most likely over heated. They recommended replacing the convertor and obtaining a used Main Control Value body and rebuilding it. I decided, while it was out of the Truck, to go ahead and do a complete overhaul. Got the truck out and it ran good for a days. On Friday at about 70 miles an hour it started vibrating, slowed down it was OK for awhile. On Saturday drove the truck about 10 miles round trip, no problems. About an hour later, on second trip the vibration started at about 40 or 50 miles an hour, I pull over to the side of the road, and race the engine, and it didn’t appear that the engine was the problem. I'm thinking convertor? But, I have no idea?
John