Dodge Rear end

> Please note that the ratio between the front and rear is NOT exactly the
> same. If, for example, the rear diff is 3.55 to 1, then the front will be
> 3.54 to 1.

Not true.... look at any HD 4x4 (where the same manufacturer is used both
front and rear), and you'll see exactly the same ratio. On my '03, it's
3.73:1 front and rear... 41 teeth on the ring gear, 11 on the pinion gear.

The reason you sometimes would up with 3.54 in the front, and 3.55 in the
rear (or 4.10/4.11) was due to the use of two different axle manufacturers.
In the Dodge world, it was Dana up front, and Chrysler in the rear (for any
1/2-ton '94-'01). For the ~3.5 gear ratio, Dana used 39 teeth on the ring
gear, 11 on the pinion, for a 3.5454 ratio. Chrysler also used the same
tooth counts, but just called their ratio 3.55:1. In the case of 4.10/4.11,
one set used 41/10, while the other used 45/11. Now, don't ask me why the
45/11 set is called 4.11, when mathematically it works out to 4.09, but
that's the way it is.

Now, why can they do this? Because 1/100th of a revolution is practically
meaningless. On a typical 30" tire, with a 4.10 gear ratio, it takes
(obviously) 4.1 rotations of the driveshaft to produce one full rotation of
the tire, covering 94.2478". That same 4.1 rotations on a 4.09 gearset is
going to produce 1.0024 revolutions, causing the tire to (attempt to) cover
94.4739", for a difference of .22" each rotation.

Now, that's the same as if both axle ratios were the same, yet one set of
tires was 30" tall, while the other was 30.071" tall. A difference in tire
diameter of seventy-one thousanths, or about 1/16 of an inch.

So, a .01 difference in axle gear ratios isn't any more significant than
having one set of tires a little more worn than the other, or inflated a
little higher/lower than the other, or simply carrying more load than the
other. It's not significant enough to cause any problems, which is why they
can be used together in a 4x4 drivetrain without issues. In this case, a
difference of only .01 is "close enough".
 >> Stay informed about: Dodge Rear end 

Tom, I have been told by multiple reputable sources of the front end being
boss requirement. Of course, I have personally never made the experiment of
trying the different combinations myself, so personally, I do not know. I do
have to say that your explanation makes more common sense and it can be
supported by your worn/different tire example. So, I will stand corrected.
This exchange also illustrates the correctness of the factory warning label
not to use 4 wheel drive during good traction conditions as well. All wheel
drives of course, use a viscous coupling to relieve the driveline stress
during speed differences from front to rear and do not wear the warning
label.
Steve

"Tom Lawrence" <tlawrence5.RemoveThis@earthlink.net> wrote in message
news:479eaa5c$0$40791$892e0abb@auth.newsreader.octanews.com...
>> Please note that the ratio between the front and rear is NOT exactly the
>> same. If, for example, the rear diff is 3.55 to 1, then the front will be
>> 3.54 to 1.
>
> Not true.... look at any HD 4x4 (where the same manufacturer is used both
> front and rear), and you'll see exactly the same ratio. On my '03, it's
> 3.73:1 front and rear... 41 teeth on the ring gear, 11 on the pinion
> gear.
>
> The reason you sometimes would up with 3.54 in the front, and 3.55 in the
> rear (or 4.10/4.11) was due to the use of two different axle
> manufacturers. In the Dodge world, it was Dana up front, and Chrysler in
> the rear (for any 1/2-ton '94-'01). For the ~3.5 gear ratio, Dana used 39
> teeth on the ring gear, 11 on the pinion, for a 3.5454 ratio. Chrysler
> also used the same tooth counts, but just called their ratio 3.55:1. In
> the case of 4.10/4.11, one set used 41/10, while the other used 45/11.
> Now, don't ask me why the 45/11 set is called 4.11, when mathematically it
> works out to 4.09, but that's the way it is.
>
> Now, why can they do this? Because 1/100th of a revolution is practically
> meaningless. On a typical 30" tire, with a 4.10 gear ratio, it takes
> (obviously) 4.1 rotations of the driveshaft to produce one full rotation
> of the tire, covering 94.2478". That same 4.1 rotations on a 4.09 gearset
> is going to produce 1.0024 revolutions, causing the tire to (attempt to)
> cover 94.4739", for a difference of .22" each rotation.
>
> Now, that's the same as if both axle ratios were the same, yet one set of
> tires was 30" tall, while the other was 30.071" tall. A difference in
> tire diameter of seventy-one thousanths, or about 1/16 of an inch.
>
> So, a .01 difference in axle gear ratios isn't any more significant than
> having one set of tires a little more worn than the other, or inflated a
> little higher/lower than the other, or simply carrying more load than the
> other. It's not significant enough to cause any problems, which is why
> they can be used together in a 4x4 drivetrain without issues. In this
> case, a difference of only .01 is "close enough".
>
>
 >> Stay informed about: Dodge Rear end 

"Steve Lusardi" <stevenospam RemoveThis @lusardi.de> wrote in message
news:fnn891$egg$03$1@news.t-online.com...
> Tom,
>So, I will stand corrected.

Said that to him a couple of times myself.<VBG>

Roy
 >> Stay informed about: Dodge Rear end 

Tom Lawrence wrote:
>> Please note that the ratio between the front and rear is NOT exactly
>> the same. If, for example, the rear diff is 3.55 to 1, then the
>> front will be 3.54 to 1.
>
> Not true.... look at any HD 4x4 (where the same manufacturer is used
> both front and rear), and you'll see exactly the same ratio. On my
> '03, it's 3.73:1 front and rear... 41 teeth on the ring gear, 11 on the
> pinion
> gear.
> The reason you sometimes would up with 3.54 in the front, and 3.55 in
> the rear (or 4.10/4.11) was due to the use of two different axle
> manufacturers. In the Dodge world, it was Dana up front, and Chrysler
> in the rear (for any 1/2-ton '94-'01). For the ~3.5 gear ratio, Dana
> used 39 teeth on the ring gear, 11 on the pinion, for a 3.5454 ratio.
> Chrysler also used the same tooth counts, but just called their ratio
> 3.55:1. In the case of 4.10/4.11, one set used 41/10, while the
> other used 45/11. Now, don't ask me why the 45/11 set is called
> 4.11, when mathematically it works out to 4.09, but that's the way it
> is.
> Now, why can they do this? Because 1/100th of a revolution is
> practically meaningless. On a typical 30" tire, with a 4.10 gear
> ratio, it takes (obviously) 4.1 rotations of the driveshaft to
> produce one full rotation of the tire, covering 94.2478". That same
> 4.1 rotations on a 4.09 gearset is going to produce 1.0024
> revolutions, causing the tire to (attempt to) cover 94.4739", for a
> difference of .22" each rotation.

My '91 Ford had 3.54 gears in the front and 3.55 gears in the rear, both
Dana 44's.
I always thought they intentionally mis-matched the gearsets to operate
automatic locking hubs. The front ratio was lower so you could lock the hubs
while driving forward and unlock them while in reverse. If the gearsets were
matched you would have to drive a very long distance (if going straight)
before the hubs would lock or unlock.
--
Ken
 >> Stay informed about: Dodge Rear end 

> My '91 Ford had 3.54 gears in the front and 3.55 gears in the rear, both
> Dana 44's.

Count the teeth... I'm willing to bet you'll find the same tooth count
(46/13), as that's all Dana lists for their 44 in ~3.5 ratio. They show a
Dana 35 that's got a 3.55 ratio (39/11).

> I always thought they intentionally mis-matched the gearsets to operate
> automatic locking hubs. The front ratio was lower so you could lock the
> hubs while driving forward and unlock them while in reverse. If the
> gearsets were matched you would have to drive a very long distance (if
> going straight) before the hubs would lock or unlock.

Auto hubs lock due to the torque input from the transfer case. There's
plenty of torque there to overcome the springs in the auto hubs, without
needing to "bind up" the drivetrain.

Again - the .01 difference is so small as to be negligible. If that was
really the desired effect, such effect could easily be undone by difference
in tire wear, tire pressure, or load (as discussed above). Remember that a
difference of just over 1/32" of tread is all that's needed to offset a .01
difference in gear ratio.
 >> Stay informed about: Dodge Rear end 

> Tom, I have been told by multiple reputable sources of the front end being
> boss requirement.

I know - I've heard that before, as well. But, I can show you pictures of
my stock 4.10 gearsets from my '99 Ram (still got 'em around here
somewhere... thought I might make clocks out of the ring gears), with the
same 41-tooth ring gears, and 10-tooth pinions. On my current truck, and
'03 with AAM9.25" up front, and AAM11.5" in the rear, both gearsets use
41/11 ring/pinion gears, for a 3.72727272 (3.73) ratio. Again, both are
exactly the same.
 >> Stay informed about: Dodge Rear end 

"Tom Lawrence" <tlawrence5 RemoveThis @earthlink.net> wrote in message
news:479facaa$0$40807$892e0abb@auth.newsreader.octanews.com...
>> My '91 Ford had 3.54 gears in the front and 3.55 gears in the rear, both
>> Dana 44's.
>
> Count the teeth... I'm willing to bet you'll find the same tooth count
> (46/13), as that's all Dana lists for their 44 in ~3.5 ratio. They show a
> Dana 35 that's got a 3.55 ratio (39/11).
>
>> I always thought they intentionally mis-matched the gearsets to operate
>> automatic locking hubs. The front ratio was lower so you could lock the
>> hubs while driving forward and unlock them while in reverse. If the
>> gearsets were matched you would have to drive a very long distance (if
>> going straight) before the hubs would lock or unlock.
>
> Auto hubs lock due to the torque input from the transfer case. There's
> plenty of torque there to overcome the springs in the auto hubs, without
> needing to "bind up" the drivetrain.
>
> Again - the .01 difference is so small as to be negligible. If that was
> really the desired effect, such effect could easily be undone by
> difference in tire wear, tire pressure, or load (as discussed above).
> Remember that a difference of just over 1/32" of tread is all that's
> needed to offset a .01 difference in gear ratio.
>

My 71 Bronco had 4.10 Dana 44 up front and a 4.11 9" Ford in back. My 79
Chevy had exactly the same ratios, Dana 60F in front, 14 bolt Chevy in back.

Al
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