Regearing to 4.88s

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What an uninformed response

I'm sure these gears fall apart then:
You obviously didn't read the linked article or you would realize (well, perhaps you would) that your example is irrelevant to the question of differentials (hint: tooth engagement). However, I will email the dumb and ignorant folks at Randy's Differentials to inform them that they don't know anything about differentials. I'm sure they will appreciate your enlightenment.
 

nukegoat

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You obviously didn't read the linked article or you would realize (well, perhaps you would) that your example is irrelevant to the question of differentials (hint: tooth engagement). However, I will email the dumb and ignorant folks at Randy's Differentials to inform them that they don't know anything about differentials. I'm sure they will appreciate your enlightenment.
Oh honey
 

abuck99

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There’s a wiff of Pirate4x4 brewing here. Mud tends to be a little more civil and less of a dick zone when opinions differ. I don’t see that changing.
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Another way to look at it: If the carrier size doens’t change; then the ring gear has to change (in depth) in order to make room for added number of teeth to increase ratio. As a result the ring gear looses strength as the ratio increases. The question is at what ratio does it pose a considerable threat to failure?

Annecdotally I dont think 4.88 poses enough weakening of the ring gear to warrant too much concern-there are plenty of 80’s &100’s running 4.88’s on 35’s+ here and not Commin to hear reports of ring gear failures (rear any way). 100 series front failures are a different story; most failures can be attributed more to user error than anything else. Thats just my opinion.
 

nukegoat

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There’s a wiff of Pirate4x4 brewing here. Mud tends to be a little more civil and less of a dick zone when opinions differ. I don’t see that changing.
- - - - - - -
Another way to look at it: If the carrier size doens’t change; then the ring gear has to change (in depth) in order to make room for added number of teeth to increase ratio. As a result the ring gear looses strength as the ratio increases. The question is at what ratio does it pose a considerable threat to failure?

Annecdotally I dont think 4.88 poses enough weakening of the ring gear to warrant too much concern-there are plenty of 80’s &100’s running 4.88’s on 35’s+ here and not Commin to hear reports of ring gear failures (rear any way). 100 series front failures are a different story; most failures can be attributed more to user error than anything else. Thats just my opinion.
Oh good sir, may I offer some constructive feedback?

First, higher ratios don't necessarily have more teeth. A 4.10 uses 41 ring gear teeth. A 7.17 uses 37 ring gear teeth.

Secondly, lower ratios, not higher ratios, require thinner ring gears, but many manufacturers can make alternatively offset carriers (aka a carrier break)

Good day sir
 
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Here is more "dumb and ignorant" information, this from the book High Performance Differentials, Axles, and Drivelines by Joseph Palazzolo. I agree regarding civil discourse here. I don't believe calling someone's post "dumb and ignorant" constitutes civil discourse. Especially when the person doing so is so easily proven wrong.

Screen Shot 2019-10-28 at 7.16.38 AM.png
 

abuck99

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Oh good sir, may I offer some constructive feedback?

First, higher ratios don't necessarily have more teeth. A 4.10 uses 41 ring gear teeth. A 7.17 uses 37 ring gear teeth.

Secondly, lower ratios, not higher ratios, require thinner ring gears, but many manufacturers can make alternatively offset carriers (aka a carrier break)

Good day sir
Got it- thanks
 

nukegoat

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Me too! I'm just waiting for any evidence from an authoritative source that a smaller pinion gear is NOT weaker.

Twiddles thumbs . . .
I have a day job, but since you're so smug...

Does the rim of a wheel get weaker when you run a smaller tire? No? Then how does the root of a pinion get weaker?

The input torque is the same to the pinion gear regardless of gear ratio, right? So why would the load seen on the root of the pinion gear vary by gear ratio?
 

nukegoat

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I dont know much about the actuals but If 4.88s were breaking, there would be threads about it........
Not to mention that r&p overload failure is almost always cause by ring gear deflection, then pinion shaft breakage, etc.

Lower gears will allow breaking spider gears and axle shafts and hub studs, sure. Those are downstream of the levers. But the gear mesh itself? The argument makes no sense if you apply any common sense
 
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Read the article to which I linked. Please? Here's the link again. Note that this is technical information from one of the most respected suppliers of aftermarket ring and pinion sets. Note that they are in the business of selling this equipment, so when they tell you about downsides it makes sense to pay attention. Set aside your preconceived notions: Common sense will actually tell you that a smaller pinion gear is weaker than a larger one, especially when fewer teeth then engage the ring gear. It's the teeth that break, not the shaft. Read the article. P.S. You STILL haven't produced any authoritative evidence to support your belief, just analogies that have no bearing on this topic.

As I said early on, most differentials have enough margin of strength to accommodate moderate regearing. It's when you start combining oversize, heavier tires with big jumps in gearing that trouble happens. And yes, I know a few Toyota truck owners who run 35-inch tires or worse and 5.29 diffs who—so far—have gotten away with it. I also know a couple of 80-year-old guys who have smoked their entire lives and are in great shape. That isn't evidence that doing either is a good idea.
 
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ClassyJalopy

Whoa! 100 series brakes are awesome!!
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@Jonathan Hanson and @nukegoat I love you both but for the love of everything holy get your own thread and duke it out to your heart's content.

As for the original question: I too run 33" AT tires and I definitely notice the loss of throttle response compared to the 30.5" ones I had on before. But all the research I have done points to changing the transfer case ratios being a better option.
 

nukegoat

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Read the article to which I linked. Please? Here's the link again. Note that this is technical information from one of the most respected suppliers of aftermarket ring and pinion sets. Note that they are in the business of selling this equipment, so when they tell you about downsides it makes sense to pay attention. Set aside your preconceived notions: Common sense will actually tell you that a smaller pinion gear is weaker than a larger one, especially when fewer teeth then engage the ring gear. It's the teeth that break, not the shaft. Read the article. P.S. You STILL haven't produced any authoritative evidence to support your belief, just analogies that have no bearing on this topic.

As I said early on, most differentials have enough margin of strength to accommodate moderate regearing. It's when you start combining oversize, heavier tires with big jumps in gearing that trouble happens. And yes, I know a few Toyota truck owners who run 35-inch tires or worse and 5.29 diffs who—so far—have gotten away with it. I also know a couple of 80-year-old guys who have smoked their entire lives and are in great shape. That isn't evidence that doing either is a good idea.
I guess you don't want to reason from first principles. That's how I approach engineering, not by posting links to Randy's ring and pinion.

Here's an important meta article for you
 
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More confirmation from this excellent resource at roundforge.com. Good information for anyone contemplating regearing. The relevant paragraph:

Screen Shot 2019-10-28 at 4.37.56 PM.png


@Jonathan Hanson and @nukegoat I love you both but for the love of everything holy get your own thread and duke it out to your heart's content.
Good advice. I'm actually finished arguing here. I've backed up my own reasonably extensive experience with the authority of those more expert than I, and I'm satisfied. Other topics to consider!
 

nukegoat

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More confirmation from this excellent resource at roundforge.com. Good information for anyone contemplating regearing. The relevant paragraph:

View attachment 2119352



Good advice. I'm actually finished arguing here. I've backed up my own reasonably extensive experience with the authority of those more expert than I, and I'm satisfied. Other topics to consider!
For anyone reading this in the future, these are not scholarly articles or engineering guides. Fortunately, we have an expert on the forum who designed and built this stuff for a living:



 
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There is a lot of overthinking going on here. 4.88 have done far too many trouble free on and off road miles in our collective 100's to stress over theoretical strength/durability. Drop that and lets talk aout the real question. 4.88 and 33" tires. @RiverRatMatt seems to have a 2000, meaning a 4spd A343F. Here is the objective simple JHS math. Common new tire: KO2 OEM size 265/75/16(or 275/70 similar) 657 revs/mile common 33" KO2 285/75 634 revs/mile.
Do the simple math of 657 x 4.30(for OEM) and 634 x 4.88(33's and 4.88 diffs) gets you to 2825 and 3098 respectively(which turns out to be the engine rpms in 3rd (1:1 ratio) at 60mph...that means 2127 and 2329 in 4th/OD(.753). It means 2828 and 3098 at 80mph. Thats the objective numbers., OEM vs 33's + 4.88 diffs. Subjectively, I put 4.88 Nitros on my 99(real world numbers equal the math)...and I love them in every way...my engine AND tranny are both acting like stock despite the 255/85's and extra weight of RTT, bumpers, mods, etc. And if you think my wife and I, or our silky smooth engine, notice the increase of 200rpms you are crazy. But we sure notice how great it runs both on and off road. High range and low range. I was looking at doing the TC underdrive, which would be +100rpms on the hwy instead of +200rpms(who cares). You will be happy with either one. Make your decision based on your specific situation. But you WILL like the way it drives after.
 
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Update: 4 more months later. Still LOVE the switch to 4.88's.. Makes all driving better, in town, off road, on the highway; the rig just feels right! And the bonus is: Using GPS numbers, I went from consistent 10mpg to consistent 11mpg. No joke, and I mean in many different conditions and many tanks of gas.
It has to be due to the transmission not having to work so hard, and lighter throttle needed to accelerate on the flats/hold speed on hills.
 
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