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Old 01-16-2013, 04:19 PM   #1
JJSporty's Avatar
Join Date: Jan 2010
Location: SoCal
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Questions About: Gear Ratios, HD Alternator, Towing Package

Hi Folks,

Iím hoping some of you more knowledgeable than me can help me here. We purchased a pre-owned 2006 SMB and Iím trying to learn as much as I can about it. Along with the vehicle, we received the original vehicle description (window sticker). On the vehicle description it lists several items under the Optional Equipment section I would like to learn more about. Here are the items I need help understanding.

1. 3.73 Ratio Limited Slip Axle: I think this is a good thing when traveling in areas where traction might be a problem. While not as good as a locker, it seems better than the stock axle for limited off-road use. I would like to know what the 3.73 Ratio means. Is this a higher or lower gear ratio than the standard axle gear ratio?

2. HD Trlr Tow Class II/III/Iv: What components are upgraded on the vehicle besides installing a trailer hitch when the vehicle was manufactured? Are other components such as engine and transmission cooling capacities increased? How about brakes etc.?

3. HD Alternator/HD Battery: Whatís the difference between the standard alternator and battery and an HD alternator and battery?

4. Auxiliary Fuel Port: What the heck is an auxiliary fuel port? I havenít a clue about what this might be but think it might be a good thing to know about should it ever come up along the way.

This forum is great and I look forward to any help any of you might be able to provide on these things.


Jeff and Janna
2014 Brilliant Silver MB Sprinter 3.0L V-6 High-Top 144 WB Modified RB-153S Espar D-5 SC Hydronic 200W Zamp Solar
SOLD 2006 White Ford E250 5.4L V8 4X2 RB-31 Modified, PH Full Length Garageable
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Old 01-16-2013, 04:42 PM   #2
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Re: Questions About: Gear Ratios, HD Alternator, Towing Pack

1) Yes, the limited slip works decently well. There are tricks to getting the most out of it (like applying the parking brake if one tire has no traction) but it is infinitely better than an open diff.

3.73 is the mid-offering for axle ratios. Good choice for a loaded van, but not the best if you will be towing a heavy trailer.

2) The components in that package includes the hard-to-add stuff. Mainly, 7-way wiring and trailer plug which includes relays and fuses to completely isolate all trailer electrical from the rest of the van. This also includes the plug under the dash to plug in a trailer brake controller. It also means you have a power steering cooler and I believe the engine oil cooler may also be part of the package.

3) This means 130A instead of 110A alternator, and higher CCA-rated (cold cranking amp) battery.

4) This provides a place to suction fuel out of the tank for aux devices like heaters or a generator. You can even use it as a fuel station for toys. It will only draw to 1/4 tank so make sure you can still drive.

2000 E450 dually V10 wagon
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Old 01-16-2013, 05:14 PM   #3
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Join Date: May 2007
Location: Turlock Ca
Posts: 10,159
Re: Questions About: Gear Ratios, HD Alternator, Towing Pack

Also gear ratios should be taken into account when changing tire (height) size.
2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer

Sportsmobile 4X4 Adventures..........On and off road adventures
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