Differential Ratio f-250

You're going to have to fix the front end, too. And, you're speedometer will not be accurate, either.

Jeff

Unless you want your truck 'a little longer'...

Yeah, i know.. that's stretching it!

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?

Well, he could have different-sized tires up front and in the back. That would take care of it.

Jeff

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.

"DeserTBoB" wrote in message news: snipped-for-privacy@4ax.com...

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.

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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

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.

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.

Or just flip over, especially at high speed.

Jeff

Not only that, but think of the better gas mileage he'd get from the truck going downhill all the time! LMAO!