Axle ratios: what does it mean?

Hello all,

I have been bit by the new truck bug. I really like the new F-150 and am currently driving a 2002 Black Sport 4x2, 4.6. I do like this truck but am fascinated by the new one with the console in the FX4 trim package. You only live once why not have a nice truck? The financing is so good now anyway.

I want to build this truck, no more take what we have on the lot only. The last time I took what was there and I don't want to do that this time. Can someone explain to me the logic behind 3.55, 3.73, or 4.10 axle ratios? Regular or Limited slip?. This truck will not be used for heavy work. I will put racks and work with it but only small trailers etc.... Which should I choose?

I like the FX4 trim package nicer than the Lariat, I am not fond of leather.

Thanks neil

Reply to
BCcubed
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3.73 should work well for your intended use.

AW

Reply to
Hattmakr

I'm sure someone else will give you a much more in depth answer, but simply put:

3.55 Ratio: When the driveshaft (pinion gear) turns 3.55 times, the rear axle (ring gear) turns once. 3.73 Ratio: When the driveshaft (pinion gear) turns 3.73 times, the rear axle (ring gear) turns once, you can see where this is going.

The more times the drive shaft turns to complete a single rotation of the rear axle, the "lower" the gearing is, and the better suited the truck is for pulling.

The less times the drive shaft turns to complete a single rotation of the rear axle, the "higher" the gearing is, and the better suited the truck for highway, and more speed.

Regular, or "open" differential, is when the rear axles turn independent of each other, one at a time receiving power from the engine, at a loss of traction, but a gain in economy.

Limited slip, is when the rear axles turn in unison, both receiving power from the engine, giving vastly better traction, at a slight loss of economy.

Not a scientific answer, but pretty much it.

Spdloader

Reply to
Spdloader
3:55 , you won't need the lower ratios for what you describe. No need to waste the gas. Of course perhaps we should qualify what you call a "small" trailer. Where I work, the small trailers weigh 4000 lbs empty. On the other hand, our dodges have 3:55's and pull these 4000 - 10000 lb trailers fine.
Reply to
Steve Barker

And my Ford has a 3.55 and pulls 10000 - 12000 lb trailers easily to. The fact that it is a PSD, might also have something to do with that.

Reply to
Tyrone

That reminds me, we have about 24,000 behind our PSD at work very regularly. I'll have to check and see what ratio it has in it.

Reply to
Steve Barker

One thing to watch out for with the 3.55, is that with the automatic overdrive, around .65:1 ratio, the engine doesn't really get into its power band, at least in my opinion. My truck turns ridiculously low rpms on the interstate, and with the small engine you're planning to get, it may not get up a hill without shifting gears or slowing down. If I lived somewhere really flat I think I'd like it, but as it is I really don't. I'm always in

3rd when I tow, so in that case it's fine.

So be sure and test drive one with the V-6/3.55 extensively before you buy. Drive it though your commute. I think you'll like it, as Steve and others have suggested, but you're not buying a powerstroke, and it may seem a little wimpy on the highway.

Reply to
Joe
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I have no practical experience with this, but have looked into it as I will be buying my first pickup and will be towing a boat and trailer weighing just under 5,000 pounds on long highway trips, as well as short trips. Regarding axle ratios, as a general rule, a Lower Axle Ratio gives you better fuel economy, is quieter, is faster and has a longer engine life, whereas a Higher Axle Ratio gives you increased pulling power, better acceleration and poorer fuel economy. Good ratios for towing are between

3.50:1 and 4.10:1. See the Towing Guide published by "TrailerBoats" magazine
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TrailerBoats also has a Tow Ratings Database which may be helpful

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According to the 2004 F-150 45-page brochure published Sept. 2003 (Ford may have made some changes since then), for the FX4 4x4, you can only get it with the Limited-Slip Rear Axle. With the P255/70R17 A/T OWL tires the

3.55:1 axle ratio is Standard and the 3.73:1 is Optional, but with bigger tires (18" wheels and also wider) you can only get the 3.73:1 axle ratio.

Whether you are going to be doing mostly highway driving or mostly off-roading (which is what the FX4 is designed for) may make a difference in your choice. Others can tell you that better than I can, but I think that the bigger tires and higher axle ratio are for better off-roading than the standard tires and 3.55:1 axle ratio.

Sandy

Reply to
Sandyon66XYZ

Well the #1 rule for towing is to turn the OD off anyway. So that should take care of that potential problem.

Reply to
Steve Barker

You have your "higher" and "lower" backwards.

Reply to
Steve Barker

Steve, I got the info from "Your Guide to Towing" (2004) published by "TrailerBoats" magazine along with SeaRay boats

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the bottom of page 16 and the top of page 17.Ford was involved in producing the Guide
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Reply to
Sandyon66XYZ

Nope, he's right on.

Higher ratio is numerically lower. 3.08:1 is a high gear

Lower ratio is numerically higher 4.10:1 is a low gear

Spdloader

Reply to
Spdloader

That's cool. It's still backwards.

Reply to
Steve Barker

I guess you meant I was right. You confirmed what I said.

Reply to
Steve Barker

I may have replied to the wrong post, not sure, but you were correct Steve.

Spdloader

Reply to
Spdloader

Reply to
Patrick Gilmore

It's always been "backwards" .

"Hi" ratios have always been smaller numbers and vicey versa.

Reply to
Keith Christensen

That sounds real safe. I hope you aren't on public roads with that rig! (I am assuming that is an F350 or less)

Reply to
Rob Munach
450 Super Crew Used daily. Triple axle 34' gooseneck loaded with trees, OR sod, OR a tractor, OR two, OR two skid loaders, OR any combination of the above.
Reply to
Steve Barker

Here's an explanation of axle ratios by Stuart Bourdon, the Towing Editor of "TrailerBoats" magazine, from the Jan. 2004 issue, page 86:

"Typically a higher gear-reduction ratio (4.10:1 or 3.73:1, as opposed to a

3.55:1) is considered better for towing. The higher the ratio, the lower the gear. Lower gears allow for quicker acceleration and greater torque mutiplication properties. It can translate to hundreds of pounds of difference in maximum trailer weight ratings. If you want the extra capacity for all the gear you haul and the boat, all other things being equal, the vehicle with the higher gear ratio (i.e., the lower gears) will be better for towing."

I had previously posted:

Regarding axle ratios, as a general rule, a Lower Axle Ratio gives you better fuel economy, is quieter, is faster and has a longer engine life, whereas a Higher Axle Ratio gives you increased pulling power, better acceleration and poorer fuel economy. Good ratios for towing are between

3.50:1 and 4.10:1. See the Towing Guide published by "TrailerBoats" magazine
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2.

Sandy

Reply to
sandyon66

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