The turntable makes noise and is jerky as it turns

Mick,
Most are a direct drive motor. You can usually turn your microwave on it's back and be able to access the drive motor through a panel on the bottom. It does have an electrical connection, so remember to unplug your microwave before working on it. Most microwave repair parts places should carry a new motor that will fit your unit. Hope this helps!

Yes it can be replaced. But first make sure the noise isn't coming from the guide roller assembly or coupler which is the plastic part in the bottom of the microwave that turns the turntable. .

Please remove the unit's turntable and clean the tray and turntable.

Possible there is friction within the drive , the shaft or the motor. You can remove and RESET the drive. Remove the motor , MANUALLY check the motion of the mechanism which will confirm the case. You c an reset using a bit of lubrication.

Try soaking the turntable when you wash up in washing up water as the wheels can cause that, otherwise replace the motor.

If you were to take the turntable coaster out and wash it in hot washing up water paying attention to the wheel surfaces, I think that will fix your problem as I suspect the wheels are uneven with deposits stuck to at least one.
Hope this helps.

Unplug unit and take bottom off of it with the screws that go around the outer edge. The turnatanble motor has 2 screws and is removabe from the bottom underneath.

The problem with turntable motor or coupler which sits on turntable motor shaft.

I’m happy to help further over the phone at https://www.6ya.com/expert/vitaliy_f406165329c75ede

You may have a tunrtable motor or spindle problem..
This info is from GE website..( link : http://genet.geappliances.com/geasearch/Dispatcher?REQUEST=GETSEARCHRESULT

To minimize the possibility of electric shock, unplug this appliance from the power supply before attempting any maintenance or cleaning.

• Make sure the turntable is centered and seated properly. On models with a stirrer motor there is a shaft protruding up through the floor of the microwave. Make sure the turntable is securely fastened to this shaft. On models that turn on a ring with wheels attached, make sure the turntable is seated securely on the ring.

• Check the turntable to make sure it is placed right side up. If the turntable plate is upside down it will drag on the floor of the microwave.

• Check to make sure that there is no food or debris under the "wheels" of the turntable ring. Food can prevent the wheels from moving forward.

• Be certain you are pressing a cook function rather than a timer function.

• If the microwave has a turntable on/off feature make sure the turntable was not inadvertently turned off. Try depressing the turntable on/off pad to re-engage the turntable.

Replace turntable motor. Not really that hard to replace or expensive. Remove all screws holding bottom panel (usually three across each side and one to three in front) to gain access to the turntable motor. The panel will hinge in the back.