Ok guys i have a 2003 F250 SD with 5.4L, 6" Skyjacker Lift w/ 37" Baja Claws. Custom exhaust from headers back all 3" tubing with 5" tips, K&N Cold Air Intake and Diablo Sport Tune. It still has the stock 3.73's in it and im finaly getting around to having the gears done. I was thinking of going to 4.56's to get close to a stock ratio. What do yall reccomend??

Dan

 

4.88 or 5.13 you have more weight and wind resistance. In your case lower will be the best. It will drastically improve power and should help with mpg. Definately make it more drivable.

 

I would go with 4.88s. The 5.4L should really have 4.30s stock, so do your math from there.

 

Even with being my daily driver 4.88's seem a little much.

When I researched the codes it came back saying it 3.73's

 

I have 4.30s with 35" tires on my 6.0L and they aren't too low. The gasser has a much higher RPM power band.

 

What gear would bring it back to a close stock ratio and give me the best mpg???

 

Not sure what you went with but I've got the 04 F250 SD 5.4 - 4" lift/35s --- just got the 4:56 done and wishing I went with at least the 4:88

 

4:88s at the absolute minimum...

getting into the 5: series is were i would look thou.

4:88s will only just get you back around stock size tire gearing.. it certainly wont make your truck feel zippy. those are big tires for that 5.4 to try to spin.

 

are 5.4's that big of turds? they have 4,5, and i believe 6 speed tranny's and they still need that low of gears for 37's? i don't know that much about them but aren't they up around 300 hp? what's the deal? no torque to match up with hp?

 

They aren't turds, but a 37" tire on a stock 3.73 rear is like trying to ride a 10 speed thats stuck in 10th gear.
The larger the tire, the steeper the gear you need.
This link may help explain...
4Lo.com :: Gear Ratio & Tire Size Chart

 

dont forget that 5.4 is lugging around the weight of the truck to..in addition to the bigger tires.

it all factors into the equation..

 

i understand gear ratios, every truck i've owned has been lifted. i know the charts, but 5.13's being suggested for 37's seems pretty steep for a street driven truck. i have 38's with a 5 spd manual and 3.55 rear end. and while 5th gear is useless to me unless i go 70 and above, i can still drive fine. and my 460 may have more torque than a 5.4, but it's only putting out 250-275 horsepower. so i don't get the 4.88&5.13 suggestions. and before you call me out i have had regeared trucks, so i'm not just being argumentative

 

everyone has different ideas of whats acceptable performance thou..

what some guys think is fine the next guy might hate..

for me i find my V10 with 35"s and 3:73 is a outrite dog.. i hate the performance of it now..

if i regear i wont even bat a eye at jumping up to 4:88's.. but i never expect to go above 35"s maybe 36"s but at 37"s my truck would become to high for what i use it for.

 

the 5.4 in my opinon is under powered in stock form. i have driven long bed, excab long bed and cclb configurations of the superduty with this engine and it will do the job but it does not do it as well as other trucks or engines. the first factor to think about when regearing is weight. the suspension and the tires add a considerable amount of weight. on top of that to maintain a highway speed with a vehicle nearly a foot taller will take more power to over come the wind resistance. both of these should negatively effect the mpgs of the truck as well as the zip or power. going to 4.56 might on paper be equivilent but you are only compensating for the gearing difference, not the added weight or wind resistance. going a step lower to 4:88 will help to offset the aditional weight and will likely give the truck as much or close to the zip it had stock. 5.13 gears will give you better drivability overall and be the best for offsetting the weight and wind resistance. yes this sounds like a lot of gear but the 5.4 makes its power higer up in the rpms compared to a big block such as the 460 or the diesel. if you are trying to run 70 you would be better suited at over 2k rpms with the 5.4. the actual difference in rpms from 4.56-4.88-5.13... will not be that great

 

Don't fear the gear. Go low, you will not regret it. I understand that you want to keep the stock feel and performance, but you have to remember that it is not just the larger tires you have to overcome; you also have the increased wind resistance from a taller ride.

I would install 5.13 gears.