So on my Dodge the rear axle is 4:10 and the front is 4:09. What is the theory behind the front wheels spinning faster than the rears?
What other makes are set up this way?

I'm pretty sure that the .01 difference will not affect performance. you're fine

I'm not concerned about the differance, they come that way from the factory and I believe I've seen GM's like that too. Just wondered what the engineers reasoning was, to keep it straight I guess. It does straighten right out when you romp it in the mucky stuff, until I blew the front r&p. :(

I think the 1% diffence stated above is the standard for the maximum gearing difference front/rear. I think it has something to do with manufacturing of the gears. Different axles have different measurement as far as pinion centerline height, ring gear thickness, etc, which makes it so that an exact, for example, 4.10 ratio can't be made for a certain axle. But a 4.09 or 4.11 would be close enough.

I think the 1% diffence stated above is the standard for the maximum gearing difference front/rear. I think it has something to do with manufacturing of the gears. Different axles have different measurement as far as pinion centerline height, ring gear thickness, etc, which makes it so that an exact, for example, 4.10 ratio can't be made for a certain axle. But a 4.09 or 4.11 would be close enough.

Mudtoy67 is right...for the most part. Also keep in mind that the gear manufacturers are rounding off their gear ratios to two decimal places. Some round up, others down, which leads to .01 discrepancies on gear ratios that, in reality, are the same ratio.

No, there is a difference in gear tooth counts. Its not from rounding the numbers.

4.09 has a 45T ring, 11T pinion
4.10 has a 41T ring, 10T pinion
4.11 has a 37T ring, 9T pinion.

The reason for it is not to make the wheels spin faster (its simply not enough of a difference), maybe its for noise or strength considerations for individual axle types, I'm not real sure though.

In the early mud bogging days we ran higher axle ratios in the front diff than the back. The theory was it would keep the rig going straight under power. All it ever did for us was break stuff we went back to the same ratios in both ends after 1 season. Still never kept straight no mater what ratio step we had. I never drove though, my job was cheif mud remover/go get me that thing, guy.

Wayne

I've always heard it was so that the front axle would pull just a little more than the rear to keep it from plowing. The front turns a little faster and pulls a little more to keep the front end up and out of the muck a little better and encourages it to climb instead of push. Don't know this to be fact, it's just what I've always heard and it kinda makes some sense.

I would think that the twisting motion of the rear end trying to lift the front off the ground would keep the front from "plowing". But maybe its just me ;)

It is just the way it works because of the design of the axles. A slight difference in air pressure in the tires or a difference in the weight on the front vs. the rear of the truck will make a lot more difference than that slight difference in gear ratio. It has NO EFFECT AT ALL.

When a vehicle is turning and the front is locked all four tires are turning at different rates. Obviously lockers/posis or being open will affect this. I believe the front tires will cover more ground (fractions of it) so the offset actually evens everything out.

It is just the way it works because of the design of the axles. A slight difference in air pressure in the tires or a difference in the weight on the front vs. the rear of the truck will make a lot more difference than that slight difference in gear ratio. It has NO EFFECT AT ALL.


I agree that this would probably have very little effect but I still find it hard to believe that the OEMs did this just for sh!ts and giggles. There must have been a reason (valid or not) that the engineers called for this tiny discrepency in ratios front to rear. I doubt it has anything to do with axle design because I've heard of all of the big three doing this upon occasion. The axles that came on those trucks could easily have been ratio matched. I don't know what axles he's running under that Dodge, but most any axle you can think of (Dana 70, 60, 44, 14 bolt [FF+SF], 12 bolt, 10 bolt, etc. and so on) have all come from the factory with 4.10s, so how could it be axle design that required the 4.09 gears? I can't help but think that they must have had some reason for doing this.

I agree that this would probably have very little effect but I still find it hard to believe that the OEMs did this just for sh!ts and giggles. There must have been a reason (valid or not) that the engineers called for this tiny discrepency in ratios front to rear. I doubt it has anything to do with axle design because I've heard of all of the big three doing this upon occasion. The axles that came on those trucks could easily have been ratio matched. I don't know what axles he's running under that Dodge, but most any axle you can think of (Dana 70, 60, 44, 14 bolt [FF+SF], 12 bolt, 10 bolt, etc. and so on) have all come from the factory with 4.10s, so how could it be axle design that required the 4.09 gears? I can't help but think that they must have had some reason for doing this.

if the 4.09 of the dana 44 front is there for some other reason then thats just the way it turned out when being designed answer this

why in almost every truck with a dana 44 front (except trucks with a 9" rear) they have matching front/rear gears in 3.31/3.54/3.73/4.56

how come my ford has a faster ratio in the rear then the front? (i.e. 3.54 front 3.50 rear)

its just they way the axle is designed. Even if it was possible to create a 4.10 and a 4.09 gear for the same exact axle it would not be usefull... when considering the specific ratio it would be more prudent to go with what will give the most favorable operation as far as the gears are concerned (i.e. strength/wear) also that little difference would quickly be negated as soon as some weight is loaded into the truck (think static loaded radius)

why in almost every truck with a dana 44 front (except trucks with a 9" rear) they have matching front/rear gears in 3.31/3.54/3.73/4.56

how come my ford has a faster ratio in the rear then the front? (i.e. 3.54 front 3.50 rear)

its just they way the axle is designed. Even if it was possible to create a 4.10 and a 4.09 gear for the same exact axle it would not be usefull...


I have no idea why you would have a higher gear in the rear than in front or have that much of a difference. I have never heard of a truck being set up that way. Are you sure it's factory gearing? Who knows? There's just no accounting for what goes on over there at the Blue Oval!!! (Just givin' ya sh!t! :))

A D44 w/4.10s? Even if it was possible??? How many D44s out there have 4.10 gears? More than sh!tloads! I have 3 D44s at the moment, and 2 of them have 4.10s and all three came out of trucks with matching ratios front to rear. One of the 3 is in my '79 Cherokee and it had a D44 at both ends, both w/ the same ratio.

I am not saying it makes a difference or it doesn't. I do not know. I'm just saying that there is probably a reason that these trucks were built that way. Maybe it's for design reasons (1 ratio gearset stronger than another), but except at the ratio extremes (like REALLY deep gears w/ a small pinion), I've never heard that before. I'd like to find out from someone who really knows. What you're saying makes some sense if in fact a 4.09 gearset is stronger than a 4.10 gearset in a D44 for example, and maybe it is but if so, I've never heard it. My 3/4 Ton Chevy p/u originally came with a 4.10 geared D44. If 4.09s are stronger, why wouldn't they have used them in a 3/4 ton application? And my truck isn't unusual. They only made about a billion (or so) just like it.

I guess I could be wrong about dana spicer 4.09 gear sets... thats what my friend had listed in his catalog...

you want to have the front pull a little faster, it helps with 4x4 steering. you know when your ripping threw a field, get way side ways, rap the gas pedal, and the front swings right around. that little bit of difference helps get that front end in place. helps alot on the asphalt with a 203 too.

chevy typicaly run a 4.09/4.11, with a smaller 28" tire it is a minimal distance of actual tire rotaition, with a bigger tire.




as for ford.......... well its ford what else would you expect.

A D44 w/4.10s? Even if it was possible??? How many D44s out there have 4.10 gears? More than sh!tloads!
I have yet to see a 4.10 D44, they're all 4.09s.

Count the ring teeth on yours, I'll bet it's 45.

well i'm sure uneven air pressure in the tires will make more of a difference than the .01 ratio will...that said, i have heard before that if the rear is spinning faster than the front it will tend to want to pass the front up as in not staying in a straight line which i guess would mean the rear spinning slower will keep it from doing that....like zukizzy mentioned earlier though, that really only applied to extreme speed mud bogging and i doubt anyone else would ever notice any benefit......as far as ratio's go for D44's, i've been looking at new gears for mine and all i ever see listed by manufacturers is 4:10, why would they not call it what it is?

i just did a lot of math, as near as i can figure a 36" [113" circumfrence]tire will have a .6" rotation differance with a 4.09/4.11 per revolution. over a 1 mile span the front 4.09 will gain 336" over the 4.11 axle.this would be a huge problem if the tires were not allowed to slip from each other. ie, turning, 203 t-case diff, rubber give, all allow the rears to catch the front. this is exactly why 205 should not be street drive in 4x4. i didnt even realize till now jut how it all added up and played together.



the above statment i made about the tire diamiter seems to have made a very insignificant difference in all of the math i did.

i just did a lot of math, as near as i can figure a 36" [113" circumfrence]tire will have a .6" rotation differance with a 4.09/4.11 per revolution. over a 1 mile span the front 4.09 will gain 336" over the 4.11 axle.this would be a huge problem if the tires were not allowed to slip from each other. ie, turning, 203 t-case diff, rubber give, all allow the rears to catch the front. this is exactly why 205 should not be street drive in 4x4. i didnt even realize till now jut how it all added up and played together.



the above statment i made about the tire diamiter seems to have made a very insignificant difference in all of the math i did.

You are also assuming the front and rear tires are the EXACT same size. This ia very unlikely.

If you need the true answer to this question try sending gearman (on this board ) a PM. I know he doesn't look in the newbie section very often.