questions regarding gear swap and locker installation...
1.) even with a minor tire size upgrade (235/70/17 to 265/70/17), will changing gear ratio help the slightest as far as mpg goes?
2.) i have open differential and i've had bad luck when it comes to wet (and steep uphill) road pavements. will locker help out a lot? as far as installation goes, how difficult is the process? i'm having my rear diff. leak fixed at ford soon and was wondering if i could have them install it at the same time.
1.) even with a minor tire size upgrade (235/70/17 to 265/70/17), will changing gear ratio help the slightest as far as mpg goes?
2.) i have open differential and i've had bad luck when it comes to wet (and steep uphill) road pavements. will locker help out a lot? as far as installation goes, how difficult is the process? i'm having my rear diff. leak fixed at ford soon and was wondering if i could have them install it at the same time.
thanks!
1) Need to know your current ratio to accurately answer this question. Just to give you a comparison. I upgraded from 275/60/17 to 285/70/17 which I also thought was a minor upgrade. Turns out is wasn't and I could really feel a loss in power even with my stock 3.55 Limited Slip. I ended up going with 4.56LS since my truck is not my daily driver and I tow\haul mostly with it.
2) My first F-150 (97') had an open diff. It sucked in the rain and snow. When I traded it in on my 02' I got the Sport package which came with a limited slip diff which is is MUCH better. I don't know if you really need a locker unless you plan on off roading a lot.
1.) with a v6 you will feel the power loss. Go 4.10 if you have 3.73 and 3.73 if you have 3.55. I would consider a programmer before you go this route. Gears aren't cheap.
2.) get a L/S as ChrisT mentioned. you dont need a locker unless you romp with your truck. Open diff's are useless.
ManualF150 went from 3.55 to 4.10 with his and he still has the stock tires - and he says it made a big difference in low end performance and his gas mileage is no worse.
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2003 F150XL 4.2 short cab/bed 4x2 5 speed manual 3.55 LS
Dont regear to get MPG it doesnt work like that and its too expensive for that.
>regear if you feel power loss from larger tires
>regear if you want better exceleration
>regear if you tow alot and need the low-end to get the weight moving
>regear MOSTLY if you dont want to toast your trans. towing heavy loads or turing heavy tires
in some situations regearing will hep your MPG in the city but most of the time it will cost you some highway MPG
I have a similar question along these lines. My 06' has a 5 speed manual transmission, a 3.31 open rear differential and stock tires. I'm looking into getting a 5' or 6'x8' enclosed trailer that'd I'd convert into an ice skate sharpening workshop (700lbs of equipment in the trailer). I'd like to be able to get power to both rear wheels to help pulling the trailer and have heard good things about the Eaton tru-trac.
Would the Tru-Trac be able to be installed in my current rear differential or what steps would I need to take to get set up?
Last edited by GoalieFergy53; 09-17-2008 at 09:11 PM.
i have the same gear as GoalieFergy53 - "3.31 regular axle". Mainly, i would love to resolve the "slipping" issue. which is a better option: LS or locker? any recommendations?
how much are we talking about here when it comes to regearing? 4 digits? why is it so expensive? will a tuner help me with my mpg issue?
I would recommend getting the LS for both of you guys. As I mentioned before, a locker is more for off roading\rock crawling, etc. The LS will really help with towing and traction issues. Detroit True Trac is a reputable brand from what I hear. I personally went with Precision gears. Both of you most likely have the Ford 8.8 axle so reference that when calling around for prices. Plan to spend about $800 - $1000 per axle, that includes parts and labor. I would say you both will be real happy with a 4.10 ratio as long as you plan on keeping your stock size tires.
the rough rate is $750/axle. on a 4x4, you have to do BOTH axles, hence the increased expense. for y'all I would recommend a 4.10 ratio. if you are 2WD, the 4.30 ratio is also an option. I wouldn't go lower than that running a (close to) stock size tire. regearing is a task that requires some special tools, and care needs to be taken for proper set up and performance. read the sticky in the "Other Powertrain" section for more info.
Goalie, 4.10's are the sweet spot for a V6 with a manual trans. I have 3.55's in mine, but its a OBS which is a lot lighter than yours. It tows "okay" but it could be a lot better. I'm happy with the factory limited slip.
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2003 F150XL 4.2 short cab/bed 4x2 5 speed manual 3.55 LS
This is definitely a great help! Since my truck is a 2wd, would I need to change both axles or just the rear? Would 4.10s be able to be installed in my current axle or would I need to get a whole new axle assembly? I'd be looking for a good shop around the Seattle-Tacoma region to have all this done. I don't have all the tools and I'm just recovering from hip surgery (and might need another!) Nothing like being 25 and going on 70!
ah thanks for the detailed info. too bad that price is out of my range. as far as installing LS, is it basically plug-and-play -> take out open and put in LS? will it just fit in there in place of the old one or is it more complicated than it looks?
and since regearing looks out of my reach (for now!), will going for a tuner be worth it?
Goalie, just the rear. I'd guess it will be in the $800 range for parts and labor to put a 4.10 LS in. Even if you had the tools, you have to know what you are doing, it's not just pull the pumpkin out and stuff a new one in there. There's a lot of clearances and alignments that have to be set up.
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2003 F150XL 4.2 short cab/bed 4x2 5 speed manual 3.55 LS
x2... if you're asking how to do this kind of job, you should research the processes extensively before even thinking about attempting it. there's about four different settings that have to be within tight specs, and changing one throws another off.
My 06' has a 5 speed manual transmission, a 3.31 open rear differential and stock tires. I'm looking into getting a 5' or 6'x8' enclosed trailer that'd I'd convert into an ice skate sharpening workshop (700lbs of equipment in the trailer). I'd like to be able to get power to both rear wheels to help pulling the trailer and have heard good things about the Eaton tru-trac. 
Since my truck is a 2wd, would I need to change both axles or just the rear? Would 4.10s be able to be installed in my current axle or would I need to get a whole new axle assembly? I'd be looking for a good shop around the Seattle-Tacoma region to have all this done. I don't have all the tools and I'm just recovering from hip surgery (and might need another!) Nothing like being 25 and going on 70! 
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