Harsh shift from 1st to 2nd when pulling away: check the throttle body
A Quickshift gearbox that shifts harshly from 1st to 2nd when pulling away immediately points to the robot. Yet the gearbox decides its shifts using information from the engine (revs, accelerator position). If that information is wrong, the gearbox reacts badly, even in perfect condition.
A real case
On a Renault Trafic Quickshift, a repairer replaced the robot and then the speed sensor, with no result at all. The cause was the throttle body, which had a dead spot. Once the throttle body was dealt with, the shifts went back to normal.
What to check before touching the gearbox
- Read the engine control unit faults too, not just the gearbox ones.
- Check the throttle body and accelerator pedal (live values on the diagnostic tool: the position must change smoothly with no jumps or dead zone).
- On diesel, check the glow plugs: failed glow plugs are also reported as a cause of limp mode.
- Only then check the gearbox: pressure, sensors, relearn procedures.
On the gearbox side: other leads
- Relearning or progressivity not done after a clutch or robot replacement: see bleeding, relearning and progressivity.
- Position or control codes: see the list of fault codes.
These observations come from workshop experience, not from a manufacturer procedure. Not sure? Our online diagnosis is free, via the website chat: it saves you buying a part you do not need.
FAQ
My gearbox shows no fault. Is that normal? Yes, it is common in this case: the fault is on the engine side, not the gearbox.
Should I replace the speed sensor? Not before checking the engine and reading its values with the diagnostic tool.