Kenmore 43142 front loader bangs during spin cycle any ideas on what the problem might be?

possibly bad counter weights

Could be a broken spring on top of the drum allowing it to hit back of casing...hope you fix...

Unless your front loader is set firmly on concrete and leveled to perfection, the force of a heavy wash load spinning in excess of 1000rpm will create a bit of vibration and noise.A firm footing is your best defense against to much movement.
Also due to the earlier movements during the spin cycle, the shocks that are used to dampen the spin cycle might have been broken or damaged.
If the problem persists inspite of proper levelling, please do check for the shocks or might have them replaced them for good.

suspect basket support broke basket will need replaceing and possible rear tub section if bearing/seal damaged overloading not usually not the cause

you may have a dampening shock that is bad

please balance your washer and use smaller loads

make sure all shipping pins are out the tub should move all around from side to side if it level still bangs its eather the balance ring top basket are there 3 slides on a plate above the motor just put some silacone oil on tham move around

The support spring beside the spinning hausing are cut replace w/new spring available appliances store. bring sample.

Laco, drop the bottom front panel and see if all of the shocks are in tact on the tub assy. They just insert and lock by turning. If these are ok, check the back belt pulley. Sometimes one of the tines will split or crack and you will get this symptom. Catriver..post back.