In a front wheel drive car (especially with an ATX and without ABS) when you apply the brakes in icy conditions, what will usually happen is your rear wheels will lock up while the fronts will continue to spin. This is because the engine is still spinning at RPM even though you are applying the brakes and not on the gas. Torque is still being transmitted to the front wheels which is overcoming the braking force being applied, while on the other hand the rear wheel locks up due to lack of weight during braking coupled with the slippery conditions.
The other side of the coin is that if you are travelling along at RPM and then suddenly lift off the gas the engine compression will immediately hook into the front wheels applying a "braking" action at the front wheels. The moment there is a significant enough mismatch between vehicle velocity/momentum and wheel rotation speed you have the beginnings of a slide.
This is why it is advantageous to have an MTX in the snow. Clutching out the power is second nature when you get into trouble and allows for you to coast out the slide and apply braking more evenly across all four tires.
For ATX drivers, if you ever get squirelly on snow and have time to react, you should immediately push your shifter into the neutral position from drive. This should allow you to coast out of the situation. Resist the temptation to apply brakes unless you really need to slow down the vehicle on top of regaining control. What you will also find is that you can shift into Neutral from Drive without even pressing the shift lockout button. The manufacturers have included it for this very reason.
On ICE all bets are off... hopefully you have reacted early enough to be able to coast it out.
In all cases for slippery conditions the rule is to apply and let off on the gas as smoothly and evenly as possible - especially at speed. Same for brakes - and look ahead and start braking early. Adjust your driving style so that you are tending to coast to stops rather than applying the brakes to stop in time.
Stay Safe All!
