Vibrations when accelerating between 80 - 110 kph

Question

2010 Fiat Ducato x250 2.3L Turbo Diesel

When accelerating between 80-110 kph the vehicle shakes. The vehicle is completely fine below 80 kph and above 110 kph. The strength of the shaking is directly proportional to the torque applied. As an example, cruising between 80-100 barely pressing the gas the shimmy is almost imperceptible. Accelerating on even ground it's noticeable but not horribly bad, however the greater the incline and the harder I press the pedal the worse it gets. So hard acceleration up a steep hill between 80-110 feels like the van will shake itself apart. \

Tie rod ends are fine. The shimmy is felt in the entire vehicle and is very violent going uphill at hard acceleration, it's not felt just in the steering wheel.

Recent work done on the vehicle:

Replaced a torn outer CV boot on driver's side front axle. Noticed there is a little in / out play perpendicular to the vehicle's body. There is no such in/out play on the passenger side axle.

All four tires balanced and new hubs / bearings / discs on rear axle.

EDIT

Checked the engine mounts and all seems fine. Put a bottle of water on top of the engine and didn't see any major splashing, no noticeable movement in the engine mounts at idle.

Answer 1

Sounds like engine mounts. You checked the engine mounts at idle, but mounts can be worn in a way that only reveals itself under load. Take the vehicle to a steep uphill highway and accelerate just until the shaking starts, then immediately downshift into a lower gear to increase the engine rpm. Does the shaking stop? If the shaking stops with higher rpm but the same road speed, it is a drive train problem, not suspension, brakes or wheels. Probably engine or transmission mounts.

Answer 2

So after reading this section in my book Automotive Service 3rd Ed. by Tim Gilles I replaced the driver's side axle and the problem went away.

I suspect that when I recently changed the outer dust boot I may have damaged the inner tripod joint. Usually when I change an outer dust boot, I undo the inner dust boot and slide it out so I don't have to drain the transmission. Then I remove the inner joint to slide the boot up onto the outer joint. When I went to remove the inner tripod joint it was so loose that it actually when I removed the circlip it just fell off...

If I have time I'll inspect the old axle and see if I can verify anything and update this answer.