How do i or what do i use to drop from 12vdc to 2vdc?

12vdc battery to a small 1.5vdc motor, d cell batteries just don't last very long, i am trying to use a 12vdc 4ah or 7ah gell cell instead.

You need a step down transformer.

Go into an eletrical hobby shop (Maplin/Tandy etc) and give them the input and output voltages you need (and any current restrictions) and they will hook you up with the correct transformer.

call an electrician

You can use a DC-Dc converter. They are available in many voltages and some have adjustable outputs.
Radio shack or online

A little gadget usually avilable in truck stops and hardware stores, it drops 12v dc to 1.5,3,4.5 6,7.5,9, and 12 vdc, also comes with adaptors and is polarity reversible. wish i could remember what it's called!!!!?

If you can solder up a circuit, buy a linear regulator and fix it up.
If not, buy a car power supply that fits in the cig lighter socket with switchable outputs like you would use for a walkman, and fix a cig lighter socket to the battery. You can buy the sockets at a trailer parts shop or similar - motor accessory or electronic components shops as well.

There are lots of little gimmicks available. The best and simplest that I can think of right off hand is to buy a small battery charger such as one used to recharge "AA" batteries for cameras. Then get the auto adapter for that which just plugs into your cars cigarette lighter socket.

First off, if you put 2vDC into a 1.5vDC motor, it won't last long before overheating and burning up. I don't know how long you need to run the motor for at any one time but here's one thing you can try to save you some time, money and greif.
ok, here's the best way. take a bunch (6) of 1.5vDC batteries. sit them togeter with all the "+" sides up in a straight line. Solder a nice piece of wire starting at one end and solder all the tops together. Make the wire a few inches longer than the row of batteries. Flip the row over and do the same to the "-" side. Now you have a 1.5vDC battery that has 6 times the life in it. It's called wiring in parrallel. If you use rechargable batteries, they'll take 6 times longer to charge but that will work too.