Drivetrain Issues:
* Worn-out U-joints: These connect the driveshaft to the axles. Worn U-joints cause vibrations, especially noticeable under acceleration. This is a very common cause of shaking in older vehicles.
* Bad Driveshaft: A bent, damaged, or unbalanced driveshaft will cause vibrations.
* Transmission Problems: A failing transmission can cause shaking, particularly when shifting or accelerating. This could be due to low transmission fluid, worn-out clutches, or other internal transmission problems. A slipping transmission is a common cause of this.
* Differential Problems: Worn gears, bearings, or a pinion bearing in the differential can lead to vibrations that are felt throughout the vehicle, especially under acceleration.
* Axle Issues: Worn wheel bearings or damaged axles can also cause shaking, particularly noticeable at higher speeds.
Engine Issues:
* Spark Plugs and Wires: Worn spark plugs or faulty ignition wires can cause misfires, leading to rough running and shaking.
* Distributor (if equipped): A failing distributor cap, rotor, or ignition coil can also contribute to misfires.
* Engine Mounts: Worn engine mounts allow the engine to move excessively, causing vibrations to transfer to the chassis.
* Balance Issues: An issue with the engine's balance (e.g., a bent connecting rod) could lead to vibrations. This is less likely but possible.
Other Potential Causes:
* Tires: Unbalanced or worn tires are a common cause of vibration. Check the tire pressure and visually inspect the tires for uneven wear. Consider rotating and balancing them.
* Wheels: Bent or damaged wheels can also cause vibrations.
* Brakes: While less likely to cause shaking *during* acceleration, warped brake rotors can sometimes contribute to vibrations, especially if the brakes are applied slightly while accelerating.
Troubleshooting Steps:
1. Start with the simplest and cheapest: Check tire pressure, visually inspect tires and wheels for damage, and consider having them rotated and balanced.
2. Check fluids: Ensure your transmission fluid level is correct and the fluid itself isn't burnt or contaminated. Low engine oil can also cause problems.
3. Listen carefully: Listen for any unusual noises (grinding, whining, etc.) while the van is running and during acceleration. This can help pinpoint the source of the problem.
4. Professional Inspection: If you can't identify the cause yourself, take the van to a mechanic for a thorough inspection. They have the tools and experience to diagnose the problem accurately.
A mechanic will likely perform a road test to assess the shaking and then inspect the drivetrain components to determine the root cause. Don't ignore the shaking, as driving with a damaged component could lead to more significant and expensive repairs later.
