This applies to front shock absorbers for the Toyota Previa (also known as Estima and Tarago) ACR30/40W and MCR30/40W that use the vehicle's original (OE) upper mount, such as STREET BASIS.
Approximately 40 mm from the top, the piston rod is shaped to fit into the hole of the OE upper mount. Please make sure that the two are perfectly aligned when you tighten the top nut, otherwise tightening will distort the hole. Although not visible at first, driving will gradually widen the distortion to a gap, and you will hear a rattling or jarring noise similar to driving with a loose top nut. If you continue driving in this condition, the upper mount as well as the piston rod may have to be replaced.