My brother's 4runner has a bad shudder coming from the auto transmission. Its bone stock with 107k on the odometer. I doubt it has ever had a transmission flush. What happens is, I am cruising along at 40-60 mph. If i take my foot off the pedal and let the rpms get low around 1-1.5k, and then accelerate slowly, the transmission emits a strong shudder that can be felt though the vehicle. However, if i floor the transmission, there is no shudder at all. It does this in 2wd/4wd with the O/D on and off.

The only odd thing i noticed about the transmission is the transmission fluid level. When the tranny was cold, and the vehicle had not moved all night, the fluid level was past the hot mark. When the transmission was hot, the fluid level was nearly twice as far up the dipstick, way past the hot mark.

Only thing i recommended to him was to get a tranny flush at the dealer and see if it was still there.