lawdawg is correct, anytime you change the overall diameter of your tires you're in effect changing the gear ratio of the vehicle, this can add extra stress on your driveline, not to mention dimish performance. Go with the 4:56's, you won't regret it.

 

Robert, I was just reading your Thread. I have a 2004 lariat screwcab with 8inches of lift on Toyo M/T 37's with the Hulk 20x10's inch rims. I am also using a super chip for added power. I am wanting to change my gearing and it seems I can't decide if I want 4.56's or 4.88's the owner at the 4x4 shop where the install would take place gave me a price or $1,000 for front and back. I do alot of highway driving and minimal towing. I just want a little better gas mileage and atleast my stock power if possible. What do you think in reference to the gears and what should I expect? And what is the best brand that would do the job. Thanks. Any input from anyone would be totally apprieciated.

 

I would at least run 4.88s with 37 inch tires. I have a friend running 4.56's with 37" tires and wishes he got 4.88s. The 4.88s will be a little better performance than the 4.56s. RPM will be about 2100-2300@70mph. $1000 front and back is a good price. What brand of gear sets are you talking about? Precision, Yukon and Richmond are all good brands. I'm using Precision myself.

 

deepblue:
I feel your pain. Went through the same decision process.
Two weeks ago had Precision 4.56s installed on my FX4 with 3.73 L/S and Nitto 325/65R18s (35").
Vast improvement. No whine and acceleration improvement is substantial.
With overdrive, RPMs are 2250-2500 at 80-85 MPH. XCal2 recalibration has speedo indicating accurately.
Ford Racing 4.56 gears are now available for 8.8 front diff and 9.77 rear. But they are mfrtd by Motive Gear. My research concluded that Precisions were preferable.
Thought I might get carbon fiber driveshaft if whine was a problem. It hasn't been (yet?) but here's a source if you want to go that way.
http://www.pstds.com/
Hope this is helpful.

 

I can't recall who said this, but.....

DON'T FEAR THE GEAR!

I run 4.56s with 32 inch tall tires and this is the way the truck should have been factory. It pulls very hard now when accelerating and on the highway it doesn't downshift out of OD on hills. I'd reccomend picking up a tuner too to optimize your shift points and account for the gear and tire size changes. It made a world of difference on mine. With 36 inch tires I wouldn't hesitate to run 4.88s.

 

 

Here's a chart:

http://www.4wheelparts.com/4wp/asset...gear-ratio.htm

Multiply rpm x .68 to get correct rpm for our trucks!

I have 33" tires and 4:56's. I love the power but I think if I had or was getting 37's I would go to a 4:88 or 5:13 ratio.

 

Whats the general consensus about which gears are the best?

 

The 3 brands I mentoned above.

 

I'm running 35's on my '02 SCrew with the 5.4. I'm thinking 4.56's to improve my towing and to fix the second gear bog since the tire change. The thing that hasnt come up in this thread is whether to have Ford do the swap and if not, how to find someone you can trust to do it right.

Whaddya think?

 

I have 4.10 in my 2002 2wd screw. I also have 20" wheels and 295/45-20 tires. I have a vibration at about 93 mph. I was told that the driveshaft needs balanced since it's turning at a faster rate than stock. I was also told to rotate the driveshaft 180 degrees to see if that stops the vibration. Any thoughts?

 

This is probably a dumb a** question, but will taking a stock 3:73 to 4:56 help your 0-60 time--And by ~ how much ? Everyone here raves that regear helps acceleration greatly, but I haven't seen anyone post some 0-60 before and after regear.

Thanks in advance .

 

To those that have researched or done the carbon fiber drive shaft, did/should it get rid of the clunk? A lot of F150 owners (including myself) keep getting their slip-yoke greased for the clunk, then it comes back the next day/week.

Thanks

 

4.56s are roughly 20% more "gear" than 3.73s, so just say they make your truck 20% faster

Haha ...

 

I have Yukon 4.56 gears with 315/70/17 BFG ATKO tires on Weld wheels. I have absolutely no wheel, tire or driveshaft vibration. Driveshaft vibration is going to be related to how fast you are trying to spin it. If you had this gearset w/stock tires you might have a vibration issue, although it seems rare to read about it here.

The 4.56 gearset puts me a little (SOP dyno) lower than the 3.73 gearset w/stock tires. My hwy mileage suffers but I am prepared to put up with it. Driving w/OD off makes a big difference rpm wise; can't say about gas mileage... I would never have bought this truck and done what I have done to it if I thought gas prices and gas mileage were worth worrying about.