I just learned how to drive manual in my 2016 Mustang GT. It has 3300 miles on it. It makes a "thud" noise when I put the stick into low gears (1,2,3) sometimes. This noise makes the car jolt, such that even passengers can feel it (similar to going over a concrete road joint).
To reproduce, I do this (for example):
- Be driving in 1st at 2500 RPM with the accelerator moderately down
- Release the accelerator completely and press the clutch to the floor
- Wait a second for the tach to drop to ~1900 (the Mustang holds it at the right RPM for the next gear up for two seconds)
- With the clutch still to the floor and the accelerator still completely released, pull the stick down into second gear
- Ease off the clutch and begin applying gas through the catch point
While doing #4, the car jolts and makes a thud noise--sometimes. It seems to do this at lower RPMs more often than higher ones. I can definitely feel it through the seat; it's not just a noise I hear.
It does not feel the same as the thud/clank I would get when I was first learning and was applying the accelerator unevenly and the car would jolt forward (which would scare me and make me let off the gas) and then would switch from being driven by the engine to driving the engine by inertia (the cross over point had slack in it, and the thud was caused by hitting the end of this slack suddenly). It could be drive train slack, but I'm not going back and forth between engine breaking and accelerating like I used to.
It is possible to reproduce this from a complete standstill: just shift into first from neutral with the clutch hard to the floor. Thud! Jolt! Then, hold the clutch down and row through the gears while stopped: 1st, 2nd, 3rd, 4th, 5th, 6th. All smooth. Back to 1st. Smooth. Drive, come to a stop, neutral, clutch, first: jolt! thud!
Why is this happening?