Bought our 01 Toyota Sequoia used in 2003 with 38K on it. Never towed with it and now has 182K on it. Last tranny service was 4 years ago at 160K and mechanic said normal wear for vehicle with those miles. This is wife's vehicle she uses daily for work and she said it recently developed a "clunk" when it shifts on occasion. She said she only notices it when she first drives it either leaving home in the morning or coming home in the afternoon from work. So I took it for a drive last evening and sure enough it slammed pretty hard into 2nd or 3rd gear after I left our driveway going down a small hill. Took it over two mountains with no slippage or further hard shifts. checked tranny fluid level and all is well. These vehicles were known to have problems with Overdrive and planetary gears but this seems to be something else. Could it be a sign of things to come like eventual tranny failure or might it be something else in the drivetrain. Has only done it for me one time so hard to diagnose but I assume it is a transmission issue.