School me on gearing

[LEB Ben]

Gonna sound like a complete newbie here...but can someone teach me a little something. I'm lookin to swap out the 3.55's I have in my Bronco for 4.56's. To my understanding, there is a 4.10 and down and a 4.10 and up carrier.

WTF is the difference between the carriers?

Is it possible to just swap carriers to a 4.10 and up and call it good? I'm thinking no issues here...but I've been wrong before.

If I want to run the same carrier...I can use thick cut gears. What is the difference between 'thick cut' and 'normal' (for lack of a better term).

Should I run the thick cuts or swap carriers?????


And while we're talking about gears...what's the difference (and what kind of application would use) between 'reverse cut' gears and 'normal gears'?

 

[blacksnapon]

Gonna sound like a complete newbie here...but can someone teach me a little something. I'm lookin to swap out the 3.55's I have in my Bronco for 4.56's. To my understanding, there is a 4.10 and down and a 4.10 and up carrier.

WTF is the difference between the carriers?

Essentially, the ring gear is larger (more teeth-larger size) you have to have a carrier larger to bolt it to.

And while we're talking about gears...what's the difference (and what kind of application would use) between 'reverse cut' gears and 'normal gears'?

Just what it sounds like, the slant of the gears go the other way.

 

[LEB Ben]

Essentially, the ring gear is larger (more teeth-larger size) you have to have a carrier larger to bolt it to..

Alright...so then it's just a clearance issue thing essentially. I figured as much...but just wanted to make sure

Just what it sounds like, the slant of the gears go the other way.

I understand that...but what is the point of them...who/what would need/want them?

 

[blacksnapon]

I understand that...but what is the point of them...who/what would need/want them?

Again, just what it sounds like, when you go into reverse.

 

[Skandocious]

Essentially, the ring gear is larger (more teeth-larger size) you have to have a carrier larger to bolt it to.

Just to clarify on what Vince said-- the diameter of the ring gear is the same for any given axle ring/pinion setup. The diameter of the ring gear is what we generally use to categorize axles, eg, Ford 9", Ford 8.8", Sterling 10.25", etc.

What varies between different gear ratios are the size and number of teeth on the ring/pinion. This is how you can identify the gear ratio if the tag is missing, by counting the teeth.

I understand that...but what is the point of them...who/what would need/want them?

Reverse rotation gears are used in some axles and some not... I think it has to do with the placement of the front pumpkin, whether it's on the driver-side (Ford) or passenger side (Chevy). My Dana 44 front axle uses reverse rotation high pinion gears.

 

[surewhynot]

On high pinion front pumpkins, reverse spiral gears are needed to make the ring mesh properly with the pinion.

 

[LEB Ben]

Alright thanks for the info and clearing things up for me guys.

 

[Fellro]

Just to clarify on what Vince said-- the diameter of the ring gear is the same for any given axle ring/pinion setup. The diameter of the ring gear is what we generally use to categorize axles, eg, Ford 9", Ford 8.8", Sterling 10.25", etc.

What varies between different gear ratios are the size and number of teeth on the ring/pinion. This is how you can identify the gear ratio if the tag is missing, by counting the teeth.

Reverse rotation gears are used in some axles and some not... I think it has to do with the placement of the front pumpkin, whether it's on the driver-side (Ford) or passenger side (Chevy). My Dana 44 front axle uses reverse rotation high pinion gears.

To expand on this just a little more, the thickness of the ring gear is different when you have the higher tooth count, therefore making the carrier change necessary. Higher numerical ratio needs a thicker gear.

Reverse cut is all for location of the pinion in relation to the carrier, on the left side requires one cut, on the right side (all in relation to the pinion now) requires an opposite cut to turn the axle the same direction. Very well likley does have to do with which side the pumpkin is on for a front axle, and sometimes, even rear axles. (I have seen offset pumpkins on rear axles on some Jeeps)

 

[1985 Ford F-150]

Jeeps up to the mid 70s all have offset drivetrain to the passenger side.

 

[flareside_thunder]

also there are kits for ford 9 inch conversions into steering axles...also another reason for reverse cut...

 

[Truckin4life]

Yes or when you put a steering axle in the rear....
Reverse cut. So your tires will turn the right way.

 

[5.0]

.

Below is a very quickly drawn, exaggerated picture to help explain the need for "thick gears" on the numerically lower carriers.

The pinion gear on the numerically lower gear sets, like a 2.75:1 for example, is often a much larger diameter than the pinion gear of a numerically higher gear set, such as a 4.56:1.

The difference in the two carriers is that the mounting point of the ring gear on the numerically higher carrier is more towards the center of the axle because the pinion gear is a smaller diameter.

In the pic below, the red and blue things are the ring and pinion, with the larger diameter pinion (numerically lower) on the left. You can see how the narrow pinion on the right actually moves the ring gear toward the center of the axle. The green thing in the left pic is what would happen if you were to install a smaller pinion (numerically higher) gearset into the numerically lower carrier. The smaller green pinion would not mesh with the ring gear, which is where the "thick gears" come in. You can use the smaller diameter pinion gear of the numerically higher ratio with the numerically lower carrier because the ring gear is actually thicker to make up for the smaller pinion.

Does any of that make sense?

 

[LEB Ben]

Thanks for the pictorial...definitely helps visualizing it.


So my question now is...is it better to swap carriers when I swap gears, or go thick cut?? Or doesn't it really matter?

 

[5.0]

And while we're talking about gears...what's the difference (and what kind of application would use) between 'reverse cut' gears and 'normal gears'?

"Reverse cut" gears were made when the hi pinion axle was made. If you were to use a standard cut gear in a front hi pinion axle, when driving forward you would be using the "coast" side of the gears, which is much weaker than the "drive" side. All reverse cut means is that the angle of the teeth of the gears are cut the other direction so you use the "drive" side of the gears when moving forward.

.

 

[LEB Ben]

Gotcha...thanks I was still a little unclear about that. I guess I didn't put 2 and 2 together between the difference of HP and LP gears.

 

[5.0]

So my question now is...is it better to swap carriers when I swap gears, or go thick cut?? Or doesn't it really matter?

What carrier do you have now? Are you wanting to upgrade the carrier?

If you plan to swap carriers anyway, just get the higher one. I don't think there is any major strength difference either way by using thick gears.

What ratio are you planning to use?

.

 

[UNRULEE]

"Reverse cut" gears were made when the hi pinion axle was made. If you were to use a standard cut gear in a front hi pinion axle, when driving forward you would be using the "coast" side of the gears, which is much weaker than the "drive" side. All reverse cut means is that the angle of the teeth of the gears are cut the other direction so you use the "drive" side of the gears when moving forward.

.

What he said.

And as to wether you want to use a different carrier or thick cut gears, I think the determining factor would be wether you want to go with the stock open diff (get the thick gear set), or if your upgrading to a LS, or a locker get the normal "thin" gear set since you'll be getting a new carrier anyway with the new added traction.

 

[LEB Ben]

What carrier do you have now? Are you wanting to upgrade the carrier?

If you plan to swap carriers anyway, just get the higher one. I don't think there is any major strength difference either way by using thick gears.

What ratio are you planning to use?

.

I have the 4.10 and down (numerically) carrier...with 3.55 gears. I wanna upgrade to 4.56 gears...so that means either go thick cut or swap carriers too. Are there pros or cons either way?


On edit...good point Lee, was planning on going with a selectable some time in the future.

 

[Skandocious]

Just a clarification Ben. The cutoff for the carrier is 3.73 and down. Anything numerically higher needs a new carrier. Hence why I needed to swap my front carrier when I swapped from 3.55s to 4.10s.

 

[LEB Ben]

Just a clarification Ben. The cutoff for the carrier is 3.73 and down. Anything numerically higher needs a new carrier. Hence why I needed to swap my front carrier when I swapped from 3.55s to 4.10s.

For your generation, I believe that's correct...I remember the shop saying something along those lines when I had Thunder's gears swapped (but that was before I knew my azz from fat meat). But for Dentsides...it's 4.10 higher/lower cutoff. Either way...I think I'm gonna skip the thought of thick cut gears, and just swap carriers.