1999 Toyota 4Runner

Soon after replacing the fluids in the front & rear differential and transfer case the vehicle-after shifting into 4-wheel drive- lost power and started jerking for a short period of time before regaining normal transmission function. This happened one time. Could insufficent replacement fluid cause this problem and/or the present problem, which is: After shifting into 2-wheel drive resistance to moving foreward upon normal gas pedal pressure. If I accelerate the car lurchers foreward in a jerking movement. I can eliminate the jerking action by first shifting into reverse before shifting into drive.I also experience this jerking action when slowing down to a stop.I would appreciate your opinion.
Walter Egbert
steelegend@aol. Com

updated 7/24/09
My mechanic-not a transmission specialist-stated the Toyota system is electronic without vacuum lines underneath. The problem as I stated is driving forward from a stop in 2-wheel drive. There doesn't seem to be a problem in 4-wheel drive (Just that one incident). Another problem I noticed today, on a wet roadway, was extreme jerking upon braking. My main concern is that I may be damaging the transmission.