Greetings. Initially, when I depress the accelerator pedal halfway, the vehicle accelerates smoothly. However, when I fully depress the accelerator, the car begins to vibrate significantly at high speeds, specifically in the 5th and 6th gears, within the range of approximately 2000 to 3000 RPM. Beyond 3000 RPM, the car accelerates normally and operates smoothly.
The vehicle operates smoothly in gears 1 through 4, exhibiting no vibrations at any speed, RPM, or accelerator pedal position.
It seems that a portion of the engine's power is not transmitted to the rear wheels, resulting in significant vibrations in the chassis until certain RPMs are reached.
Actions undertaken:
Four new tires
All new brake discs and pads
New crankshaft pulley
New engine mounts and gearbox mount
Flywheel and clutch mechanism
EGR and EGR cooler
Propshaft central bearing
The mechanic examined and tested the vehicle, and I was informed that there are no concerns.
Propshaft Suspension
Propeller shaft joint
Both driveshafts
No diagnostic trouble codes present
I am interested in any ideas or if someone has had a similar situation. Thank you! I have extensively researched related subjects but cannot locate any information on that particular topic.