Any structural difference between 3.31, 3.55 and 3.73?
07-23-2010, 08:08 PM
#3
5th Gear Member
Join Date: Jun 2007
Location: Decatur AL USA
Posts: 2,176
Technically taller gears (numerically smaller) are stronger and of course their is less torque multiplication so is easier on the axles but harder on the driveline forward of the axle. But really you are splitting hairs.
08-12-2010, 03:02 PM
#5
Ford builds all there gears to equal strength. However like GT Premi mentioned only Ford gears can be held to such a high standard, other manufacturers though can not.
08-12-2010, 04:56 PM
#6
I guess a better question is how much torque can each gear take?
As mentioned above, metallurgy and materials science must be balance with gear ratio or the gears will fail.
For example, lets say that 3.31 gears can take 500 ft-lbf torque before it breaks. Using the very same materials, same amount of material, gear pitch, etc, the 3.73 gears might only be able to take 475 ft-lbf before they break.
The 3.73 can be reinforced to take the same 500 ft-lbf by using thicker gear teeth (pitch), making the ring gear thicker so it will not snap, etc.
So, based on this logic, I pose the same question the OP asks, except in a more focused parameter:
What torque can is each gear designed to take?
3.31 can take ____ ft-lbf
3.55 can take ____ ft-lbf
3.73 can take ____ ft-lbf
If anyone knows, please post.
As mentioned above, metallurgy and materials science must be balance with gear ratio or the gears will fail.
For example, lets say that 3.31 gears can take 500 ft-lbf torque before it breaks. Using the very same materials, same amount of material, gear pitch, etc, the 3.73 gears might only be able to take 475 ft-lbf before they break.
The 3.73 can be reinforced to take the same 500 ft-lbf by using thicker gear teeth (pitch), making the ring gear thicker so it will not snap, etc.
So, based on this logic, I pose the same question the OP asks, except in a more focused parameter:
What torque can is each gear designed to take?
3.31 can take ____ ft-lbf
3.55 can take ____ ft-lbf
3.73 can take ____ ft-lbf
If anyone knows, please post.
08-13-2010, 12:53 PM
#7
3rd Gear Member
Join Date: Jul 2006
Location:
Posts: 880
Great Question!!!! I would like to know this as well!
I guess a better question is how much torque can each gear take?
As mentioned above, metallurgy and materials science must be balance with gear ratio or the gears will fail.
For example, lets say that 3.31 gears can take 500 ft-lbf torque before it breaks. Using the very same materials, same amount of material, gear pitch, etc, the 3.73 gears might only be able to take 475 ft-lbf before they break.
The 3.73 can be reinforced to take the same 500 ft-lbf by using thicker gear teeth (pitch), making the ring gear thicker so it will not snap, etc.
So, based on this logic, I pose the same question the OP asks, except in a more focused parameter:
What torque can is each gear designed to take?
3.31 can take ____ ft-lbf
3.55 can take ____ ft-lbf
3.73 can take ____ ft-lbf
If anyone knows, please post.
As mentioned above, metallurgy and materials science must be balance with gear ratio or the gears will fail.
For example, lets say that 3.31 gears can take 500 ft-lbf torque before it breaks. Using the very same materials, same amount of material, gear pitch, etc, the 3.73 gears might only be able to take 475 ft-lbf before they break.
The 3.73 can be reinforced to take the same 500 ft-lbf by using thicker gear teeth (pitch), making the ring gear thicker so it will not snap, etc.
So, based on this logic, I pose the same question the OP asks, except in a more focused parameter:
What torque can is each gear designed to take?
3.31 can take ____ ft-lbf
3.55 can take ____ ft-lbf
3.73 can take ____ ft-lbf
If anyone knows, please post.
08-13-2010, 03:42 PM
#8
Cut & Paste Expert
Join Date: May 2007
Location: NW Arkansas
Posts: 13,322
Thicker ring gear means smaller pinion gear to compensate for
the same housing size. Ring gets stronger, pinion gets weaker.
The more pinion teeth you have the less of a contact patch.
So as you go more teeth on the ring and less on the pinion,
or the other way around, the torque multiplications goes
the other way an equal amount,
it all equals out as for the gears strength differences
in the same housing.
Now change the available space in the differential pumpkin
and that though goes out the window.
the same housing size. Ring gets stronger, pinion gets weaker.
The more pinion teeth you have the less of a contact patch.
So as you go more teeth on the ring and less on the pinion,
or the other way around, the torque multiplications goes
the other way an equal amount,
it all equals out as for the gears strength differences
in the same housing.
Now change the available space in the differential pumpkin
and that though goes out the window.
08-15-2010, 03:45 PM
#9
I meant thicker in the plane of the ring diameter, not in the plane perpendicular to the ring diameter. Yes, going thicker on the plane perpendicular to the ring diameter would encroach on space that is already determined by the diff housing dims.
But br making the ring thicker going towards the center of the diameter, that is what I meant. You also elongate the teeth on the pinion and the ring gear which also allows you to distribute more load over more material, thus adding strength in that respect.
To preserve the diff housing dims, I meant that going with a thicker ring not on the plane perpendicular to the ring diameter and not making the ring thicker radially outwards. I meant making the ring thicker radially inwards.
Likewise, so you can present more tooth front contact area, you extend the pinion gear accordingly.
But br making the ring thicker going towards the center of the diameter, that is what I meant. You also elongate the teeth on the pinion and the ring gear which also allows you to distribute more load over more material, thus adding strength in that respect.
To preserve the diff housing dims, I meant that going with a thicker ring not on the plane perpendicular to the ring diameter and not making the ring thicker radially outwards. I meant making the ring thicker radially inwards.
Likewise, so you can present more tooth front contact area, you extend the pinion gear accordingly.
Thread
Thread Starter
Forum
Replies
Last Post
mrappe
V6 (1994-2004) Mustangs
0
09-26-2015 10:16 AM
mungodrums
Suspension
0
09-24-2015 10:12 PM
