I have a Whirlpool washer model WTW4950XW2 that will not spin out during a wash cycle.
I defeated the lid lock and watched it through a cycle. I used 6 t-shirts of the same size and distributed them evenly.
It would fill, agitate, and drain OK. Then in the rinse cycle it would fail.
What it is suppose to be doing during the rinse cycle is spin, stop, spin, stop while it fills with water. What it does is start to spin, then the lidlock light will start to blink. It never does spin. It would then finish adding water, stop for a while, drain and then stop for good.
It does this no matter what wash cycle I use. It does it on the "Rinse and Spin" cycle also. It will also do it on the "Drain and Spin" cycle if the clothes are too wet. But once they dry enough the "Drain and Spin" cycle will work OK.

I got a service manual. I cleared the error codes out so that I could see current errors for the current failure. The only error that pops up after a failure is "Basket Speed Sensor Fault". I've ran the same load for different cycles and still same results and error codes.

I ran the Automatic test and it went OK. I ran Manual test and they went Ok. I ran the Low Spin, High Spin, Gentle Agitation, Heavy Agitation test for two minutes and no failures. I played around with the lid lock during the test and could not get it to fail. If I run a spin test with wet clothes, it will fail.

I ran a calibration with an empty drum. Then ran a wash cycle with clothes and the failure returned.

I pulled and looked at the drain pump, shift actuator, belt, lid lock and they all look OK. I pulled the drum ring and looked between the drum and tub. It looked clean. The drum will freely spin by hand. The suspension rods look OK. I reseated all the connectors. I pulled and blew into the water level hose and it is clear. The washer sets level.

Through the service manual I ran test on pretty much everything. All the voltages, resistances and continuities are OK. The only thing I noticed was that the test on the control board had me look at the diagnostic LED to see if it was ON. It never was on. The manual never indicated if that was a bad thing or not. It just had me do the next step.

So I'm kinda at my wits end. I've boiled it down to being either the control board, belt, actuator, motor, harness, lid lock, splutch pulley or something else I haven't thought of. See what I mean about being at my wits end. Too many parts to order to test out.

I'm wondering if it might be the belt. The belt looks OK and it seems to be tight. But I'm wondering if the belt might slip during the initial thrust that occur during spooling up a spin. With no clothes it does OK with dry clothes it does Ok but with wet clothes it fails. Maybe the weight of the wet clothes causes too much inertia and then causes the belt to slip. The splutch pulley has black marks on it where the ribs of the belt have ridden on it.

Any help would be greatly appreciated.