I drive a 07 SC'd' Harley and want to swap out the gears to more "Speed" friendly gears. I don't tow anything on a usual basis other than my jet ski which requires no effort from the truck. I was looking to change gears so that i can see more "umpf" in my take off. I'd like to have it geared so when i stomp the gas those rear tires go to spinning.

 

4.10 or 4.30 depending on how much highway driving you do.

 

the only Hwy driving I do is a 600-1000 mile trip once or twice a year driving to and from school. And do you have an idea what it's gonna cost to have this done? Parts and install etc.

 

I depends on if you have AWD or just 2WD.

http://www.americantrucks.com/motive...430-gears.html

$219 for just the ring and pinion, and I'm guessing that since yours is a higher end F150, I'd say that you've already got a LSD. Install prices are still the biggest factor, especially nowadays. It could cost anywhere from $400 to $600 just to install everything IF you have every single part and the master install kit.

 

My truck is 2wd I don't think they made supercharged Awd's. And this might sound really stupid but what is a LSD. I'm extremely Noob when it comes to powertrain. So i'm looking at under $1000 to have this done? One more quick question, What's the difference in 4.10 and 4.30's

 

LSD = Limited Slip Differential

What are your current gears? If you don't know, look at the door jamb sticker for the axle code.

 

Assuming I've looked at the correct spot i believe it says Axle "B6"

 

Ok welcome to Powertrain 101!

A LSD is short for Limited Slip Differential. A LSD is a mix between an open differential and a locker.

An open differential is really only good for street use with no ice or snow. When one tire looses traction, all the power goes to that wheel. So if you get stuck, you stay stuck. The only positive is that you can go around turns smoothly and silently.

Lockers, on the other hand, are used primarily for off-road and straight line racing use only. Both axles are locked which makes it so that both wheels get an equal amount of power at all times. If used on streets, there can be unneeded stress on the axles due to binding.

A limited is a nice balance between the two. A LSD can be used both for street and off-road use, but is better for street use. As the name says, slippage is limited so that the loose tire doesn't receive most of the power that can leave you stranded. On the streets, you can still go around corners like you would with an open diff, but there can be a light chattering because the clutches, but is easily resolved with friction modifier.

There are few different styles of LSD's that are available for your truck. I only know of the clutch-types and gear types. Ford's Trac Lok uses clutches, while the high end Detroit True Trak's use gears. I think the True Trak is geared (no pun) more towards off road use while the Trac Lok's are better for street use.

Now we can discuss gear ratio's found in axles.

The number designated to ring and pinion sets represents the number of revolutions that the driveshaft spins for 1 revolution of the rear axle. 3.55 gears are better for highway cruising, while 4.30's are great for city driving or racing. 4.30's have the potential for increasing MPG's, but when you pass a certain threshold, the engine is reving higher to maintain it's speed which consume more fuel.

I mimght have to take back my previous recommendation for 4.30's in your case. The rule of thumb for the Mustang guys is 4.10 for forced induction and 4.30's for N/A. You're already pushing some power with that blower, and 4.10's will improve the low end. Of course it's your call.

You can also post your door code that should have your axle code. That way we can tell you what ratio you've got and if you've got a LSD.

 

Hopefully this is the door tag your talking about

 

Ok, it's a 3.73 with a LSD. Going from 3.73 to 4.10 really won't be noticeable enough to justify the costs. I'm going to have re-recommend 4.30's.

 

Alrighty. So i should be able to swap out to 4.30's for under a grand?

 

If you shop around you can definitely get it all done for under a grand.

 

Thanks for all the help bro! Now one more question and i'll leave you alone. Why should I run 4.30's and not 4.56's I see all the 4wd guys with big tires re-gearing to 4.56's whats the difference?

 

What size tire are you running? I can give you an idea what it will do to your cruise rpm. If it's the tire size on your door sticker, here are the rpm for the various ratios in overdrive.

mph 3.73 4.10 4.30 4.56
70 2005 2204 2311 2451
85 2435 2676 2807 2977

Personally, I wouldn't go more than 4.10.

 

4WD guys run 4.56's because they've lost so much low end because of their big tires and wheels. Plus they don't make the 4.30 gear set for their front axles. There is one guy who has a 2WD with 4.56 gears in the back, but I've never had the chance to interview him about the subject, and he's never on. I'm sure his RPM's would be pretty high when cruising.