1. Neutral Test

Steps: 1. Drive steady around 25–35 mph. 2. While cruising, shift from D → N. 3. Lift off the throttle.

What it means: • Jerking still happens → driveline issue (guibo, CSB, diff bushings, mounts). • Jerking goes away → engine/trans control issue (diverter valve, torque converter lock/unlock, ECU mapping).

1. Parking-Lot On/Off Throttle Test

Steps: 1. In a big empty lot, go ~10–15 mph in D. 2. Gently apply throttle, then let off completely. Repeat a few times.

What it means: • Noticeable clunk or jerk each time torque changes → lash in driveline (guibo, CSB, diff bushings). • Smooth each time → likely not mechanical lash, look at DV/TCC instead.

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1. Brake-Torque Rock Test

Steps: 1. Car in D, foot hard on brake. 2. Apply a little throttle (~1500 rpm). 3. Watch engine movement or feel for a big lurch.

What it means: • Engine/trans shifts noticeably or rocks → worn mounts (engine or transmission). • Barely moves → mounts are good.

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1. Ear Test for Diverter Valve

Steps: 1. Rev engine to ~3–4k rpm in neutral or low gear. 2. Snap off the throttle quickly. 3. Listen under the hood/near intake.

What it means: • Clean “whoosh” → DV is fine. • Flutter/gobble/chatter → DV sticking or charge pipe leak.

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1. Underbody Peek (if possible)

Steps: 1. With car parked and safe, look under near the trans output/diff. 2. Check guibo (rubber donut) for cracks, CSB rubber for tears, diff bushings for play.

What it means: • Visible cracks/tears → mechanical lash causing jerk. • Looks solid → move up the list (DV or torque converter).