How could I .....
 

... Run a 6V rated servo using a 7.4V battery pack? Since the servo fits perfectly and the 2 cell pack provides 7.4V, I dont want to viod the warranty. I dont know how I would do it =/

Like this:

http://www.teamnovak.com/products/BEC/index.html

So to use it I just plug it into the reciever?

In between Batt and RX.

Is it for a nitro or electric car?

An electric car ;)

You'll need to remove one of the leads from the ESC to the receiver as well so that the ESC is not providing voltage to the receiver. I believe it's the white wire, but double check your ESC's manual. Also, here's another reccomendation for the voltage regulator:

http://www.horizonhobby.com/Products...rodID=LOSB9608

There's one available w/o a switch too. If you're using a LiPo receiver pack you should also use a voltage cutoff too in order to prevent over-discharging the receiver pack:
http://www.horizonhobby.com/Products...ProdID=NOV5470

Before you go doing anything, answer a couple of questions: Is the 7.4V battery I'll assume it's a LiPo) driving the car? Is it connected to an electronic speed control (ESC)? If the answer to both is yes, then you don't really need to do anything as the ESC will drop the voltage down for the receiver and in turn, your servo.

Depending on what ESC you have will depend on what voltage and current it puts out. Basic models will only do 5V @ 1A, the better ones will do 5.5 - 6V @ 3A.

I guess the issue is if your servo can run off the lower voltage. Most will, but will not be as fast as they are at 6V.

Good one. The white wire is the signal wire. The red wire is the + wire, black is the - wire. Some brands use different colours.

I'll be using the Spectum Micro Reciever, Xcelorin 1/36 ESC and BL motor and the HS-45hb Hitec Servo. The pack is a 2 cell 7.4V Li-Ion one (see here) It is running the car, not just the reciever.

Let me know what I need to do, and which BEC.

Thanks for your hekp so far, but I'm still confused on what to do =D

you don't need to do anything!

you plug the 7.4v battery into your esc
the esc automatically lowers the voltage to your reciever and servo. this has been standard esc functionality for many years.

in a nitro car, you may need an esc if you aren't using a 4 or 5 cell nicd/nimh radio batt.

Oh great, thanks =]