Hey i noticed alot you guys talk about gearing a truck differently, can you guys explain it to me, like if i have uhm i think its 4:10 gears now, why would i want to go with 3:73:1 (haha im almost positive i miss typed that) ???? i noticed that garret talks about going to that gear set up in his vulger display of power post.

 

I dont think I could epxlain it well, but i have 3.55 gears stock. I would move up to 3.73's, youd be moving down.

 

It is a reference to the final drive ratio thru the rear differential.
For example: a 4.10 rear end rotates the axle 1 time for every 4.10 revolutions of the drive shaft. This is good for towing.
A 3.55 rear end turns the axle 1 time for every 3.55 revolutions of the drive shaft.
The 3.55 is a good all around compromise. Next (IMHO) would be a 3.73.
Compare it to riding a 10 speed bike in 1st gear, 3rd gear, 5th gear. relate the number of times you turn the crank (pedal power) to how many times the rear wheel truns.
Get the picture?

 

So then what would be your ideal gears Brian??

Garrett

 

Garrett,
Sorry for the delay. I have been out of town.
Ideal all depends on what you want to do.
If you are concerned about grunt off th eline or towing (or 1/4 mile times) in general, the 4.11 rear end is what is used.
I can't remember for sure, but I think Ford offered a 3.07 with the 4.2. Towing capacity is awful, but lower RPMs on the freeway and in general, better MPG. But remember, lower RPMs can have your truck well below where it makes decent power, so downshifting on hills would be more necessary.
My truck has the 3.55. It serves me well since I do tow occasionally, but drive many interstate miles each year as well. Next choice for me would be 3.73.
My truck "prefers" to cruise at about 78 MPH on the freeway. That is about 2400 RPM and the engine seems very comfortable and smooth there.
(As a side note, with the 3.55 rear end and 255X70-16 tires, you are turning 32 RPM for every MPH in 5th gear)
Personally, I'd NEVER go below 3.55 in a truck. You can click on the SPECS link on the right hand border and look at the differences in towing capacity bewteen the rear ends.
Thanks!


edit to add: It is 3.08, not 3.07. Here's a link to the model year for my truck.https://www.ford-trucks.com/specs/2000_f150_1.html
Interesting to note that nothing above 3.55 was offered. my guess is CAFE would suffer.

 

So then if you were a drag racing man, what gear would you drop in? I am thinking 3.73's, mainly because I hear 4.10s are the best for non-towing every day drivers....Any input anyone?

Garrett

 

Since you're getting supercharged I think the 3.73's will be good for you. They help at low RPM's, and you won't run out of gear by the end of the 1/4.

 

Garrett,

You also have to watch your tire size diameter. If you running a 29 inch tire, your rpms will be much higher than with say a 32" tire. This also effects your gearing. The bigger tire you put on the rear, the slower it's going to make your truck off the line and the bigger gear you should drop in the back.

if your running stock 30.5" tires on your truck, I would drop the 4.10's in. You not going to notice anything going to a 3.73, it's too small of a difference from the 3.55's.

As you know, I have the 4.10's in my truck and am running very small tires at 29". I have no problem hitting 120mph on the highway with this gearing. I can also cruise all day long at 90 mph.

Gas mileage on the highway will be less. i'm averaging 15-16 mpg combined city/highway driving. Which is average for a large automatic truck like mine. I actually didn't notice much gas mileage change when I put the 4.10's on.

Now, I'm about to install those 32" Super Swampers. This is now going to slow my truck down and make my rear end perform as if I had the stock 3.55's in. I may, at that point, decide to go with the 4.56's in order to return my low end grunt.

4.10's are the standard upgrade for most F150's, regardless of engine size.

If you post a poll on this site, I think you'll see that most people are running this gear. This is a very popular gear and I know that you will be happy with its performance.

Don't waste your money on the 3.73's.

Wait until you get your super charger installed and see what that does to your low end torque. If your completely satisfied with it, then don't change a thing. If your truck still feels a little sluggish off the start, then have the 4.10's installed.

If I end up going to the 4.56's, I'll sell you my 4.10's for 75 bucks.

Tom

 

Tom is correct, tire size is a direct player in figuring your OVERALL final drive ratio.
You can get the same effect drive ratio (or darned close) with taller tires and lower rear end gearing.
I tend to agree with him on the 4.10 rear end. If you are going to be looking at 1/4 mile times, I'd figure you'd want the 4.10 gears. Not much of a jump going from 3.55 to 3.73 gears.
But, as mentioned, you might run out of motor by the end of the 1/4 mile with the 4.10 rear end, especially if you are running short tires. But, apparently Tom has that set up and it works for him.
For me, my truck will never see a drag strip. It might see 3-400 miles of Interstate on any given day. I like the 3.55 as I believe it is the best all-around compromise. I can cruise at 80, turning about 2500 RPM and get about 16 MPG. About the same as Tom gets.
Whatever works for you, go with it!

 

Super Swamper has a chart that measures gear ratios to rpms and torque vs gas mileage. It's a pretty interesting chart. You look at your tire diameter, cross reference it with your gear ratio, and you can see whether your in the high torque range, the middle every day range, or the high gas mileage range. This may help you decide which gear ratio you want to use. Assuming that your stock tire size is 30 inches and running 3.55's, your on the bottom end of very low torque and high gas mileage. You can jump to 4.10's with no problem.

It's an interesting and very helpful chart. I just came accross it.

check it out. We can use this for many future references. I saved it in my favorites.

http://www.intercotire.com/html/table.htm

Tom

 

sometimes I amaze myself.

But then, other times i'm just an idiot

Tom

 

Thats incredible..I wanna slap on 4.56's with a 14" honda civic rim with low-pro's...any thoughts on that?

I will measure the diameter of my entire wheel, right? I have 265/70/16's right now...BFG's to think about it.

Garrett

 

No, just from one side to another.

There is a more specific way though.

Find out what model BF's you got and go to their website. On their website they will post the exact spec's of that tire in your size. It will list the distance per revolution as well as the diameter. This will give you an exact measurement.

Actually, visit this page. Your diameter is 30.6" if you've got the Radial Long Trail T/A's as I suspect.

http://www.bfgoodrichtires.com/asset...g_trail_ta.pdf

 

Dude,

Those Super Swampers are 3" bigger than my current tires......PLUS they weigh a massive 450 pounds for the 4. Man, forget about racing my truck with these tires on....NO WAY. I'm going to be slow slow slow. So, I may have to through those 4.56's in...we'll see.

 

Thats what I meant about the kissing the 1/4 mile comment!!! LoL. I have the Rugged Trails, not Long trails. Not sure if theres a difference.

Garrett