Rear End Gear Ratios

1 Dollar · Apr 14, 2009

I have an 5 speed F-150 (4X4) that currently has a 3.55 rear end. Would it make a BIG difference if I broke down and put 4.11 gears in it? It is a daily driver and pulls a trailer 1-2 times a week during the warm months. Im guessing it would be $700? total to have it done?

How much of a difference would .56 make?

Thanks

mattofvinings · Apr 14, 2009

Personally I don't think I'd do it as your fuel economy suffers every single day of the week.

Add to this the fact that you really need to change the FWD axle ratio to match too...while 4x4 mode relies on some front wheel slip to work thru steering/turns, you'd be slipping a lot in a straight line with the front axle trying to overdrive the rear axle. I know I don't use 4wd that much...but I need it to work properly when I need it.

PhilipIN · Apr 15, 2009

What year is your truck? Look in your owners manual or find the sales brochure. When I ordered my truck I could choose a 3:73 with a 6900# trailer rating or a 4:11 with a 8400# trailer rating. I chose the 4:11. See what the difference is for your truck, make your decision. Philip.

edj856 · Apr 15, 2009

How does your truck do when you're pulling your trailer? If you're not pulling a trailer everyday, I would leave it alone. If the truck is struggling with the trailer, you may want to look into a truck with a bigger engine. You will get a little better fuel mileage and not lose your top end speed with the 3.55 gears. Depending on tire sizes and your OD gear ratio, you may end up with your engine screaming just to do 65 mph if you go with the 4.11's. You could probably find a calculator online that will figure out your engine speed if you know the tire size, axle ratio, and transmission ratio.

As mattofvinings said, you will also need to change the gears in the front rear.

Dell (WA) · Apr 22, 2009

Dollar.......gotta 5-speed eh? and you feel OVERLOADED in top-gear eh? Just don't use top-gear when towing yer HEAVY trailer. Simple and cheap, eh? BTW, the difference between top-gear and 4th gear is usually about 0.40......Dell

john_Bud · Apr 26, 2009

You are about 1/2 of the cost to swap gears. Remember it's both front and rear. Also, you should change seals and maybe bearings when you pull the axles and front wheel "u-joints".

Just use 4th gear 1:1 vs the .8 OD (or so) gear.

4.11 * .8 = 3.28

So, a 4.11:1 gear set in 5th is about the same as 3.55:1 in 4th. If you wanted to determine the mpg effects of that change, drive a couple tanks where you never go to 5th. glug glug glug

mkirsch · Apr 29, 2009

The only thing you gain by going to 4.11's is a lower 1st gear. Unless you're having problems getting the load moving in the first place, it's not worth it.

I've got 3.42s on my Chevy and I simply leave the auto trans in 3rd with the tow haul mode on, instead of Drive.

charles todd · May 9, 2009

I use a Chevy K1500 (4x4) to haul my gooseneck trailer. I pull cargo+trailer 12,000 - 16,000 lbs on occasion. I have 3.73 gears and slightly oversized tires making my ratio about a 3.62 (used a calculator). It is an auto and I tow in 3rd with tow/haul feature on.

I have not had any problems, I just take my time. Running in 3rd with a load I get about 10-11 mpg. Empty I get about 14-15 mpg. I wish I had the 4.11's. It is not true that they only help in "1st gear" they bring the engine RPM's up to keep the engine in its max powerband. Towing at 2000 rpm ain't gonna cut it, sorry it won't. My old Chevy C20 is a 350 4bbl with a TH400 behind 3.73's. It tachs 3000 rpms at 65-70 mph. It doesn't back down from hills.

Charles

Rear End Gear Ratios

1 Dollar

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mattofvinings

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PhilipIN

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edj856

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Dell (WA)

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john_Bud

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mkirsch

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charles todd

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