Whirlpool tub pump only runs in slow speed

At the end of the wash/rinse programmes the drum would turn slowly while the pump removes the majority of the water and when the tub is virtually empty the drum will begin building speed over time until the spin speed is reached. The pump remains running until the end of the spin. That is how things usually go.

An automatic washer doesn't drain - it is pumped out!

Your description suggests either there is something wrong with the pump or programmer.

http://www.aquaglass.com/product-assets/installation-manuals/07397%20All%20Whirlpools.pdf

it is a air switch, it has a tube running from the button to a box mounted on the pump motor,it could the hose has came off

First check the breaker box for the house and see if it has power.

You will need to install a special controller if you change to a 2 speed. Because there will be an additional wire (4 wires vs. 3) with a 2nd speed to operate.
If you go with a variable speed motor, then again, a special controller will be required to utilize a reo-stat type of switch with will allow a selection of slowly increasing voltage to motor which will in turn allow the motor to spin quicker.

Instead of the hassle above, just go with a "One deal package" all nicely bundled ready for installation. It has it all within it - What...? A variable speed complete pump! That will be the sweetest thing for you if you are looking to go that route!
Check these out...
Aqua Leisure Relax in Comfort Pool Lounges

Good Luck

First of all, what you have is a WOW pump that has an E-switch for a control.
There is a knob on the top lip of your tub that you turn a 1/4 turn to turn this pump on/off.
There is a small circuit board inside the box on top of the motor. This is likely the source of your problem.
Here is your biggest problem. That little circuit board is not made anymore. We have the e-switch but you will be better off changing out the pump (which you have to do anyway) with a new WOW pump with an air switch and change the switch on the top lip of the tub to an air button which will turn the pump on/off.

Rod
US Parts Center

You could easily have the whirlpool fed by a double breaker. Try turning it off and back on and see if all is back to normal

What model of pump? Pumps are changed and identified by the model and brand name of the pump, NOT the model number of the bath tub.

Rod

US Parts Center

888-521-6183

will have to remove access panel or make one the motor /pump assembly is mounted to the tub test for power to the switch and pump the numbers u are looking for are their by pump