Car shakes / vibrates

[Trolkar]

Any advice is welcome!

My dear Legnum has always had a bit of a shaky ride, and now the ”To do list” off what to change is almost empty.

The body of the car shakes. Mostly at around 75-80 km/h in 5. Gear (1750 rpm) – (It is a automatic), and pretty much every time when driving in the city. The shaky feelings is not in the steering wheel, but is felt “all over the car”. I am pretty hysterical with my car, and have felt these vibrations the past year, and a lot of effort has been put into the car, trying to solve the problem. But today even my wife and kids noticed the vibration.

When in “N”, you can feel a small vibrations, when idling the engine at around 1500-2000 rpm. – Mostly “around 1700-1800 rpm”. But the strange thing is, when watching, or if I lay my hand on the engine, it is dead still. – Nothing to feel.
Almost everything has been changed. Of cause the tires has been balanced, and every driveshaft, inner and outer joints, convertor and shocks has also been changed. Still no improvement.
So last week, even the gearbox was changed. – Still vibrations, and in fact maybe a little more? (Since the wife and children never had mention it before today.)
The gearbox is “of cause” running Amsoil ATF.

What have were missed changing?

[Humpty's Revenge]

Any advice is welcome!

My dear Legnum has always had a bit of a shaky ride, and now the ”To do list” off what to change is almost empty.

The body of the car shakes. Mostly at around 75-80 km/h in 5. Gear (1750 rpm) – (It is a automatic), and pretty much every time when driving in the city. The shaky feelings is not in the steering wheel, but is felt “all over the car”. I am pretty hysterical with my car, and have felt these vibrations the past year, and a lot of effort has been put into the car, trying to solve the problem. But today even my wife and kids noticed the vibration.

When in “N”, you can feel a small vibrations, when idling the engine at around 1500-2000 rpm. – Mostly “around 1700-1800 rpm”. But the strange thing is, when watching, or if I lay my hand on the engine, it is dead still. – Nothing to feel.
Almost everything has been changed. Of cause the tires has been balanced, and every driveshaft, inner and outer joints, convertor and shocks has also been changed. Still no improvement.
So last week, even the gearbox was changed. – Still vibrations, and in fact maybe a little more? (Since the wife and children never had mention it before today.)
The gearbox is “of cause” running Amsoil ATF.

What have were missed changing?

Engine mounts ??

[elnevio]

As apparently not a gearbox problem caused by Dexron III, because you have already used Amsoil ATF, then I think Steve is in the right ballpark with the engine mounts suggestion. If they are original, there is a good chance that they are sagging and/or disintegrating.

[Trolkar]

All engine mounts are brand new :-( - Not more than 6 months old.

[Trolkar]

The converter has also been balanced.

[Humpty's Revenge]

Transfer box ?

Front/rear struts, movement in top bushes ?

Out of balance prop shaft ?

Air con pulley ?

Front struts sitting to low on the wishbone ?

Bolt missing somewhere ?

Gearbox replacement still shagged ?

Torque converter ?

Flywheel bolts loss ?

[Gly]

wheels/tyres?

[Davezj]

The vibration you are experiencing is probably going to be due to harmonic standing waves, the resonant frequency or certain parts are occurring at the same time and building up to create a larger vibration than the sum of all the smaller vibrations. I say this because the vibration is only occurring at one particular rpm range.

I had a vibration on the engine/gearbox and it was the bolt holding the torque converter to the engine hand come loose after all the hard driving I had put it through.

When the gear box nd torque converter were out did you replace the torque converter seal?

When the engine mounts were changed when they changed for OEM mounts or polly mounts?

The polly mounts can cause extra vibration into the car, but I have never seen it be any more than slight vibrate at idle but you never know.
Did the harmonic damper and tie bar get refitted when the engine mounts were changed?
We're the engine and gearbox mount refitted correctly. E.g. did one get fitted then done up to the max then the next get fitted nd done up to the max, etc, etc. What should happen is all the mount are fitted let the engine settle into it's normal position then do the bolts up tight. If it not allowed to settle the engine car be twisted out of alignment and massive extra pressure put on the mounts which can cause them to fail very quickly, or just be out of alignment and it is the metal case of the mount contacting the chassis.

Is the front cross member bent a bit so it come in contact with the bottom of the gearbox at certain rpm's.

Wheels and tyres, a buckled rim or tyre out of shape, or just bad balance. If you feel the vibration through the seat the this suggest rear wheel balance is out. jack the rear of the car up spin the wheels and check the inside of the rim for buckles and out of shame tyres.

Just a few thoughts.