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Jun 3rd, 2008 Q&A

Submited by Anonymous

What is a “cat back” exhaust system and what benefits does it provide?

“Cat back” exhaust refers to a complete system from the original catalytic converter on your vehicle and back. Removing the catalytic converter is illegal in most if not all states, which is why you hear so much about a “cat back” system. A benefit of replacing your exhaust system from the catalytic converter back is increased airflow if you go with a system (pipe) that is larger than what you have from the factory. Most systems (gas) start stock at 1 ¾ to 2-inch with a semi-restrictive muffler, so moving to a 2.5 to 3-inch pipe with a high flow muffler will help “exhaust” the air flow that your vehicle produces. Most diesel applications come stock with a 3-inch, so upgrading to a 4-inch pipe and a high flow muffler will really help that turbo diesel move down the road. Check with the exhaust manufacturers out there to see what one will work best for your application.

Submited by Anonymous

I want to install bigger tires and wheels on my SUV but I heard it makes the speedometer inaccurate. How to I correct the speedometer to indicate the correct speed with the new wheels/tires?

Yes, changing out your tires will affect the reading on your speedometer, and there are several ways to correct this. Some of the newer trucks and SUV’s that are all computer driven just need to have the computer re-programmed with your new tire/wheel sizes. This can be done with an aftermarket programmer, or some dealerships can and will do it for you, but be warned they will charge you to do so, and it will probably cost just as much as buying an aftermarket programmer than has more benefits to the vehicle than just correcting your speedo.

For those of you with older vehicles that are not 100% computer driven (Jeeps 2005 and older and trucks/SUV’s 1997 and older), you will have to change out the “Speedo Gear.” The Speedo gear ratio you need will depend on the size of your tires, so consult with your local ASE mechanic to ensure that you get the right gear for your application.

Submited by Anonymous

How often should I service the front differential in my four wheel drive SUV? I hardly ever use the four wheel drive.

As always, consult with your vehicle owner’s guide first and foremost as each vehicle is different. For example, the newer truck and SUV manufacturers publish a 100,000 no service needed, which is something that I disagree with if you like your vehicle and want it to keep running. If you rarely use the 4x4 you can get away with servicing it every 25,000 – 30,000 miles. If you’re an avid off-roader or live in the snow-belted states where it is on 4-7 days a week during the winter, I suggest changing out the fluids every 10,000 miles, and have your mechanic (or yourself) check for any water in the fluids.

Information contained in this communication is of a general nature and is subject to change without notice. Information is not intended to provide professional advice or to take the place of licensed professionals. You are encouraged to consult with a licensed professional about your particular circumstance prior to acting on any of the information contained herein. OPTIMA Batteries, Inc., makes no warranties, express or implied regarding the accuracy of information contained in this communication, and assumes no liability for loss or, damage (including death) resulting from the use of information herein.

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