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Car Forum / Ford / Ford Cars / November 2006Differential Ratio f-250
2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear end. I would like to see about changing it to a 4.11 or so ratio in. Wondering what I would have to do. Buy an entire rear end assembly? Some portions within? Where to purchase? Also. It's 4wd. Do I need to change the front end too? > 2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear > end. I would like to see about changing it to a 4.11 or so ratio in. > Wondering what I would have to do. Buy an entire rear end assembly? Some > portions within? Where to purchase? Also. It's 4wd. Do I need to change > the front end too? You're going to have to fix the front end, too. And, you're speedometer will not be accurate, either. Jeff > You're going to have to fix the front end, too. .. > > Jeff Unless you want your truck 'a little longer'... Yeah, i know.. that's stretching it!  SignatureYeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price you pay..DEAL with it! >2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear >end. I would like to see about changing it to a 4.11 or so ratio in. >Wondering what I would have to do. Buy an entire rear end assembly? Some >portions within? Where to purchase? Also. It's 4wd. Do I need to change >the front end too? <snip> Too funny! Watch this maroon put a 4.10 (Danas don't come in the 4.11 flavor, nimrod) and leave the front a 3.56! With 3.56, running normal sized (not idiot size) tires, you'll be running more that 3600 RPM at road speed. In this day and age, who the hell would want to do that? >>2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear >>end. I would like to see about changing it to a 4.11 or so ratio in. [quoted text clipped - 8 lines] > running more that 3600 RPM at road speed. In this day and age, who > the hell would want to do that? Well, he could have different-sized tires up front and in the back. That would take care of it. Jeff >>>2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear >>>end. I would like to see about changing it to a 4.11 or so ratio in. [quoted text clipped - 11 lines] >Well, he could have different-sized tires up front and in the back. That >would take care of it. <snip> Not only that, but think of the better gas mileage he'd get from the truck going downhill all the time! LMAO! >>2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear >>end. I would like to see about changing it to a 4.11 or so ratio in. [quoted text clipped - 8 lines] >running more that 3600 RPM at road speed. In this day and age, who >the hell would want to do that? Probably because he IS running 'idiot tires' now and can't get out of his own shadow off the line. You do have to change the final drive gears at both ends at once - and they have to match exactly if you will be on semi-solid dirt with the 4WD engaged to avoid powertrain wrap-up and eventually breaking something. If you only lock up 4WD in soft sand or mud conditions, the ratios can be slightly different (Dana front and Ford rear and an exact match is not available). But 4.10:1 and 3:56:1 are too far apart for this to work, even if you try staggering tire sizes - If the tires can't slip in the sand you'll be chewing up whatever is the weakest part in the driveline on a regular basis, be it u-joints, or yokes, or slip-splines or other driveshaft or axle parts, or a gear in the transfer case... Two comments: The higher the truck, the easier it falls over - you quickly reach the point where it looks bitchin', but totally unsafe to drive because a stiff wind will roll it. Try not to cross that line - if you seriously think about stenciling "Bigfoot" on the doors, it's too late. And changing the rear end ratio helps with acceleration when you change to massive tires - but it does nothing for stopping, and the tires affect the effective braking ratio the same way... Upgrade the brakes, or you'll end up in a steaming heap of trouble the first time you need to stop Right NOW and you can't. --<< Bruce >>-- <...> > You do have to change the final drive gears at both ends at once - > and they have to match exactly if you will be on semi-solid dirt with > the 4WD engaged to avoid powertrain wrap-up and eventually breaking > something. If you only lock up 4WD in soft sand or mud conditions, > the ratios can be slightly different (Dana front and Ford rear and an > exact match is not available). Does the manufacturer matter? I think the ratio is determined by the number of teeth on the gears, so it should not matter who makes them. > But 4.10:1 and 3:56:1 are too far apart for this to work, even if > you try staggering tire sizes - If the tires can't slip in the sand [quoted text clipped - 7 lines] > if you seriously think about stenciling "Bigfoot" on the doors, it's > too late. If you are going down that route, there are other newsgroups or forums that are better suited to your needs than this one. Not to say that the people here aren't excellent. Jeff > And changing the rear end ratio helps with acceleration when you > change to massive tires - but it does nothing for stopping, and the [quoted text clipped - 3 lines] > > --<< Bruce >>-- ><...> > [quoted text clipped - 7 lines] >Does the manufacturer matter? I think the ratio is determined by the number >of teeth on the gears, so it should not matter who makes them. Where the problem comes in with different axle manufacturers and models is the overall ring gear sizes are different, so while one axle maker might offer a 4.10 gear, the closest the other maker might get is a 4.11. If the two axle's gear ratios are off a hundredth or two like that it's not a big deal, wheel slip can fix that. But if it's off by over a tenth (my estimate of where big trouble starts, YMMV) like 4.11 in the front and 4.27 in the rear, you start having trouble with driveline wrap-up - the front wheels go "faster" than the rear or vice versa. This builds stress in the driveshafts and transfer case that gets relieved one of two ways: Either a tire slips in the dirt, or something breaks. Which is why you NEVER lock up 4WD on dry pavement - they can't slip. (You hit this mostly in aftermarket 4X4 conversions {IE QuadraVan}, junkyard axles and body swaps - most OEM vehicle manufacturers pick complimentary axles out of their "parts bins" where they can easily get several matching ratios at both ends, just to avoid this issue.) You get the same effect while turning, even if the final-drive ratios match perfectly - If you draw out the arcs that the wheels take on the pavement in a turn, all four wheels are turning at slightly different rates. The tighter the turn and the longer the wheelbase, the more pronounced the effect. The front end tires are turning a bit faster than the rear overall because of the rear axle 'cheat' - this is best seen (it's much more exaggerated) in turns with a commercial tractor and 40' plus long semi-trailer, where the tractor has to swing really wide and the trailer tires barely clear the curb. If you crank the turn hard enough with the tractor, you can make the trailer axle pivot in place, or even go backwards. --<< Bruce >>-- >><...> >> [quoted text clipped - 14 lines] > is a 4.11. If the two axle's gear ratios are off a hundredth or two > like that it's not a big deal, wheel slip can fix that. But how could the gears be off? The gears have so many teeth. It is the ratio of teeth on one gear to the teeth on the other gear that counts. One gear maker is not going to make a gear with say 41 teeth while another will have 42 teeth. A 4.10 rear end should turn the tires 1 revolution for every 4.1 revolutions the drive shaft turns. http://auto.howstuffworks.com/differential.htm > But if it's off by over a tenth (my estimate of where big trouble > starts, YMMV) like 4.11 in the front and 4.27 in the rear, you start > having trouble with driveline wrap-up - the front wheels go "faster" > than the rear or vice versa. This builds stress in the driveshafts > and transfer case that gets relieved one of two ways: Either a tire > slips in the dirt, or something breaks. Actually, you get wrapup just when you go around a turn. The back tires take a shorter distance around than the front ones. ANd on dry pavement going strait, the wheels will still rotate at slightly different speeds, depending on air pressure, weight on the tires, speed of acceleration, braking and wear of the tires. > Which is why you NEVER lock up 4WD on dry pavement - they can't slip. Depends on the maker of the 4WD. Some 4WD systems are meant to run on dry pavement. My '84 AMC Eagle had one that was meant to go on dry pavement. What matters is whether or not the transfer case allows slippage or not. Of course, the 4WD system on an AMC Eagle was not designed to handle the same type of conditions as a truck, and vice versa. The Eagle's 4WD system had limited slip between the front and rear axles. Many lock up between the front and rear. > (You hit this mostly in aftermarket 4X4 conversions {IE QuadraVan}, > junkyard axles and body swaps - most OEM vehicle manufacturers pick [quoted text clipped - 12 lines] > semi-trailer, where the tractor has to swing really wide and the > trailer tires barely clear the curb. Or just flip over, especially at high speed. Jeff > If you crank the turn hard enough with the tractor, you can make the > trailer axle pivot in place, or even go backwards. > > --<< Bruce >>-- So Deser TBoB you are quite the impressive dude are you not? Sorry for livin that I did not know Dana does not have a 4.11. They do have a 4.10. I guess that makes me a nimrod. So what are you? I guess you are just TOO smart for everyone. In case you did not know the standard ration is 3.73. SO what the bloody hell do you know about RPM's at road speed in a 4 speed auto Ford. OK with the rear end that is in there you are going way over 100mph to read 3600 in 4th. Now maybe you feel safe driving at that speed in a pickup and if you do Everybody else should look out cause youl will probably kill them all. Or maybe you travel highway in 2nd gear? Basically the truck revs at 2k at 72 mph or so and this stinks for drivin anywhere but western Ohio where the only hills are on the bridges that cross the highway. Real annoying shifting from 3rd to 4th with no load at 70 with moderate hills. Slightly higher rear end may give a few more revs and cut down on the shifting annoyance. And by the way they are stock tires 255 16's Thank you Bruce for at least being civil. > >2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear > >end. I would like to see about changing it to a 4.11 or so ratio in. [quoted text clipped - 8 lines] > running more that 3600 RPM at road speed. In this day and age, who > the hell would want to do that? I have a 1994 F-350 4x4 and I looked into that already (I wanted yo put dualies on my truck). You would have to change both the front & rear axle, OR change the ring & pinion in your existing axles. If you have both front & rear disc brakes, it could be more than 2k (just for the parts). In either event, you are looking at spending way more than $2,000. I don't think that Dana was installed on 2003's. In any event, unless you have $ to burn, you had probably forget about switching out your axles. Just my 2 cents. ============================================== >2003 f-250 Super Duty. This has a lousy 3.58 or something like that rear >end. I would like to see about changing it to a 4.11 or so ratio in. >Wondering what I would have to do. Buy an entire rear end assembly? Some >portions within? Where to purchase? Also. It's 4wd. Do I need to change >the front end too? |
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