My drill go's at a slow speed ,even when fully charged

Sounds like the switch is not making good contact.

You have to check the batteries with a new machine. If the new machine works ok then the rotor of the motor of the old machine is broken.

The speed switch on top may be in between speeds. Try it in a different speed. If not the top switch, the the trigger may be bad. Does reverse work?

Its much more likely that your batteries are not charging up properly. Ni-CD batteries suffer from 'memory effect' and can appear fully charged when only 70% charged. Also they lose charge when being stored. Do not short them out to discharge them! Wait until the drill complains that they are flat and then recharge them rather than when they first start to slow down. Do not let become completely flat (less than 1 volt).

It depends on the charger taht comes with this drill, the dumb charger will just keep on charging the batteries even when it if fully charge and does not sop, which will be bad for the batteries, the smart charger (more expensive and has electronics inside the charger) will go into floating charge when the batteries are fully charge which will prevent the batteries from being overcharged. If in doubt, remove it from the charger after overnight charging.

At first it does sound like the batteries.

How old is the drill? If it's old, then the batteries may either be dead, or need a careful, slow charge overnight to charge them properly. If new, then they may also need a really nice slow charge.

Sorry to ask, but have you fully charged all the batteries you have tried? !!! Many rechargeables lose a great portion of their charge if they sit for a long time.

Also, when using the drill, never use it until it runs the battery down so far stops, as this can damage batteries or discharge them to where again you need to very carefully charge them to get full charge back again.

Have you overloaded the drill:any plastic smells or have you drilled too hard and stalled it for a long time? That could cause motor damage. But look to the batteries first.

the battery's are most likely dead, (like the real dead) after many uses of rechargeable battery's they slow stop holding charge at all, make sure when you get a new rechargeable battery you fully charge it once and fully discharge it once this will increase batterys life time

It is possible that it might not be wired correctly, but I doubt it. I would return for replacement or warranty repair.

Does the drill do anything? Check in the cavity where the battery goes and make sure there is nothing there to prevent the battery contacts from connecting with switch. I take it the charger indicates the batterys are fully charged. If you cant see anything obvious I would take it back and get a replacement.
Dave