Options for those who want overdrive on their TJ (42RLE vs AW4 vs ?)

[Ashim]

Getting back to the original post, what is your current tire size and gearing? My auto 2004 Rubicon has 35's and 5.13 gears, runs about 2500 RPM at 70 MPH, exact parameters you wanted. I drive it to trails out of state on the interstates, rarely want to go over 70 due to noise and the fact that fuel consumption increases greatly at higher speeds. Average 14.5 MPG on the highway.

Years ago, had a club member that fitted an AW4 into his 2002 sport auto. Required a lot of wiring changes and then found that the Jeep needed to be regeared afterwards due to the OD. In the end I don't believe it helped much with highway mileage.

 

[mrblaine]

Strange that the AW4 would act any different in an XJ than a TJ since it literally has no way of telling what vehicle it is in. Wonder if it has something to do with specific combinations.

It has to do with the inability of folks to evaluate something accurately and be objective about it. I had a helper who worked with me for many years, very smart guy, very observant, easily able to figure out the what and the why of stuff. He helped me do several AW-4 swaps, he was aware of the pitfalls. He had a TJ he was building up, he wanted OD. He spent a couple of years trying to get me to sell him the set of swap parts I had, I resisted until finally I sold it all to him. We got it all swapped in and working perfectly. I bugged him every single day about how it was. He said it was the greatest thing he had done so far.

He had a friend he was helping build a rig. They wound up with near identical rigs, same tire size, similar wheelbase, very similar weight, only difference that really mattered was the transmission. His buddy had the 42RLE. They got his buddy's rig built up well enough to start going to JV and went. He called me when he got back and explained that now he finally understood what I meant about robbing power. His buddy walked off and left him on the runs out to the trails like he was dragging an anchor. He is one of those who is very competitive and hates to lose so this was a heartbreaking admission for him but I was glad to see him finally recognize the truth.

It is very easy to be fooled when you have very strong confirmation bias. It is very difficult to admit that all the work you just did doesn't really deliver the intended results. I have no problem being objective and I'll never do another AW-4 swap into a TJ. Before I put my foot down, I did my best to talk the last few owners out of doing the swap. All my logic fell on deaf ears and was met with the "the internets say it is the best thing ever". To the point where I would send them emails with lots of warnings that finished with not to bother me when all the crap I was saying about the swap came true.

The last owner called me after his first trip to the mountains very unhappy with me. I asked him if he had email access at the moment. He said he did. I dug up the email and sent it again and had him read it while we were on the phone. Oh, I see, all the things you told me were going to happen did happen.

Yes sir, that is correct, I did my best to convince you not to do this and you ignored all of it. I wish I would have listened. So do I.

To date, of all the swaps I've done, only 2 are still in the vehicles. My personal and my helper's, but he sold the rig, The rest have been removed.

As to why, we don't know. My personal is and has been at a trans shop for longer than is prudent so they can try and make it tolerable with a different stall converter and some valve body mods. I've done swaps in all the groups of TJ's. Early, middle, and the 05-06. Makes no difference. My XJ buddy suggested that perhaps the XJ PCM made the difference. I located one in the same year as Kat's rig and we tested it. No difference.

The common issue is the cruise control won't work if you leave the manual trans PCM in the rig. When the converter unlocks to run up a slight grade easier, the manual PCM thinks you've pushed in the clutch and kicks out the cruise. I had Kat's reprogrammed to not do that. That's all just to point out that we've tried to solve the swap problems with a bunch more work that we get credit for.

 

[machoheadgames]

Not any more than I can fathom why when you take a perfectly wonderful AW-4 out of the XJ where it has few if any faults and then it falls on it face the second you toss it into a TJ. I can absolutely tell you that axle ratio doesn't matter except to make it worse as they get higher. (lower numerically)

As I've stated many times, I have a friend who is Mr. XJ. I was explaining the problem and pondering possible solutions. He was mystified. I had him take Kat's for a spin. He came back and wanted to know WTF was wrong with it. He said it acts like it is dragging an anchor and that's with 5.38's and 35's.

I’ve wondered about this. The XJ was tuned for a bit more horsepower and torque…not a lot but sometimes that makes a noticeable difference. Wonder if that plus the aerodynamics make the difference?

And I’m assuming the XJs we are saying perform wonderfully are probably stock on 28” street tires?

Although this still doesn’t explain the lagging performance when you have 21.5% more torque advantage via the 5.38 gears over the 28’s and 3.55s that XJs came with. Beats me.

 

[mrblaine]

I’ve wondered about this. The XJ was tuned for a bit more horsepower and torque…not a lot but sometimes that makes a noticeable difference. Wonder if that plus the aerodynamics make the difference?

There was a gent who modified valve bodies. It was supposed to wake it right up and make it work very well. He disappeared never to be heard from again but everyone who had his parts raved about them. I tried to get one and failed. I seriously doubt any tuning in the PCM will have enough effect to overcome how terrible they are.

And I’m assuming the XJs we are saying perform wonderfully are probably stock on 28” street tires?

Yes, I had a 99 for Kat as a daily and it was more than perfectly fine. Everytime I drove it I always wondered about the why. But, I'm over it. I've reached the limits of my patience, tolerance and ability to solve that problem.

 

[machoheadgames]

There was a gent who modified valve bodies. It was supposed to wake it right up and make it work very well. He disappeared never to be heard from again but everyone who had his parts raved about them. I tried to get one and failed. I seriously doubt any tuning in the PCM will have enough effect to overcome how terrible they are.

Yes, I had a 99 for Kat as a daily and it was more than perfectly fine. Everytime I drove it I always wondered about the why. But, I'm over it. I've reached the limits of my patience, tolerance and ability to solve that problem.

No sense in investing any more brainpower into it. Even if it could work well performance wise, there’s still the crappy harmonic balancer CPS, manual TC lockup, and every other qualm that comes with the swap.

 

[Negreac]

No sense in investing any more brainpower into it. Even if it could work well performance wise, there’s still the crappy harmonic balancer CPS, manual TC lockup, and every other qualm that comes with the swap.

Can you elaborate on the "Crappy Harmonic Balancer, CPS and Manual TC Lockup"? I've not found these issues referenced in any of my research on the AW4 swaps, would like to add them to the cons.

In regards to the AW4 acting differently in the XJ vs the TJ, I would think a full stand alone TCU could help narrow it down to controls or something physically within the trans.

I know @RustyAutoholicGuy has been running an AW4 with the HGM Compushift stand alone TCU as well as the valve body of a Toyota A340F. Would be curious if he has experienced the same inefficiencies with all the modifications he has done to his AW4 setup. Granted it is behind a Diesel not a 4.0L.

 

[Negreac]

Getting back to the original post, what is your current tire size and gearing? My auto 2004 Rubicon has 35's and 5.13 gears, runs about 2500 RPM at 70 MPH, exact parameters you wanted. I drive it to trails out of state on the interstates, rarely want to go over 70 due to noise and the fact that fuel consumption increases greatly at higher speeds. Average 14.5 MPG on the highway.

Years ago, had a club member that fitted an AW4 into his 2002 sport auto. Required a lot of wiring changes and then found that the Jeep needed to be regeared afterwards due to the OD. In the end I don't believe it helped much with highway mileage.

You have the 42RLE from factory. Below is your setup vs stock. Very nice configuration. Only thing I can think of that would make it even more adaptable is adding a Rubicrawler. This would add a higher 4-low (2.72:1) and a extremely 4-low (10.88:1). So you would have:

1. 4-H-L (RC engaged and NV241OR in 4 high) - 2.72:1 - 39.63 crawl ratio - 1.76mph @ 700rpm
2. 4-L (RC disengaged and NV241OR in 4 low) - 4.00:1 - 58.28 crawl ratio - 1.20mph @ 700rpm
3. 4-L-L (RC engaged and NV241OR in 4 low) - 10.88:1 - 158.51 crawl ratio - 0.44mph @ 700rpm

If you ever did this though I would just be careful with the skinny pedal in 4-lo-lo since with that much torque multiplication you could very well start breaking things downstream of your T-case. You already are already running a weaker ring/pinion than the factory 4.10 with the 5.13 (the deeper the gear the the less tooth contact and more susceptible to breakage) and you would be 272% of the torque multiplication of the factory 4-low 4.00:1

BTW the reason you are running 2500 RPM at 70mph instead of the ~2400 in the chart is probably because your 35s aren't actually 35s and closer to 34s if measured.

What is your experience with the OD and the shifting of the 42RLE with your setup? Have seen many complain about it but most with your gearing seem to be happy with how it reacts on freeway and around town.

 

[mrblaine]

You already are already running a weaker ring/pinion than the factory 4.10 with the 5.13 (the deeper the gear the the less tooth contact and more susceptible to breakage) and you would be 272% of the torque multiplication of the factory 4-low 4.00:1

Out of curiosity, why doesn't first gear in a manual transmission break every single time you leave from a stop, even with some spirited enthusiastic acceleration?

It has the smallest gear driving the biggest gear which has to violate the number of teeth in contact rule, so why don't they break? What would happen if you did the same bit of enthusiasm and tried to launch from 3rd or 4th gear? Your logic says those are the strongest or much stronger gears, so what would happen?

 

[machoheadgames]

Can you elaborate on the "Crappy Harmonic Balancer, CPS and Manual TC Lockup"? I've not found these issues referenced in any of my research on the AW4 swaps, would like to add them to the cons.

It's been a long time since I read up on that swap. Blaine can probably address both as I seem to recall reading the initial info from him to begin with. I forget if the TCC needed to be controlled manually or if splicing in the XJ TCM takes care of that. I just remember it being a topic of discussion. As for the harmonic balancer comment, I don't know what platforms or years require it but I vaguely recall some needing to run a kit from HESCO that moves the crank position sensor over to the harmonic balancer and reads crank position there instead. The word crappy comes into play because that kit is not known for working very well and starts to stumble somewhere around 3800 rpm because it can't keep up.

I don't know what the conditions are for needing the crank sensor relocation. Last time I looked at AW4s, it appeared that it used the same 2-bolt sensor in the same 10:00ish position that my AX15 used, so I would think some Jeeps don't need to do anything to run the AW4 successfully. I know the sensor moved down to about the 4:00 position on the 6 speed manuals, maybe it's installing an AW4 on those that is the issue? I'm not sure. @mrblaine, do you recall?

If you ever did this though I would just be careful with the skinny pedal in 4-lo-lo since with that much torque multiplication you could very well start breaking things downstream of your T-case. You already are already running a weaker ring/pinion than the factory 4.10 with the 5.13 (the deeper the gear the the less tooth contact and more susceptible to breakage) and you would be 272% of the torque multiplication of the factory 4-low 4.00:1

This doesn't really matter. I mean it does eventually, but if it gets to the point it matters, it will show up on any ring and pinion ratio, and will not show up on a lower ring and pinion first. the lower gears, the smaller the teeth, but consequently, the lesser the amount of torque on the teeth due to leverage. It balances out to make most all the ring and pinion ratios about the same effective "strength." the short answer is that you don't want to use the skinny pedal too much with a rubicrawler or similar, regardless of what your axle ratio is. The axle ratio being whatever it is makes no real difference to the risk.

BTW the reason you are running 2500 RPM at 70mph instead of the ~2400 in the chart is probably because your 35s aren't actually 35s and closer to 34s if measured.

I have yet to see a 35" tire anywhere close to 35", most are 33.5". Same for 33's, most are 31.5-31.7". If you are targeting so specifically to be at 2500 rpm, I would factor that in appropriately or you may not land where you want. Personally, I would absolutely want more than 2500 rpm on the highway. Even with more than 2500 downshifting will still be frequent for anything but a very minor grade.

 

[mrblaine]

It's been a long time since I read up on that swap. Blaine can probably address both as I seem to recall reading the initial info from him to begin with. I forget if the TCC needed to be controlled manually or if splicing in the XJ TCM takes care of that. I just remember it being a topic of discussion. As for the harmonic balancer comment, I don't know what platforms or years require it but I vaguely recall some needing to run a kit from HESCO that moves the crank position sensor over to the harmonic balancer and reads crank position there instead. The word crappy comes into play because that kit is not known for working very well and starts to stumble somewhere around 3800 rpm because it can't keep up.

I don't know what the conditions are for needing the crank sensor relocation. Last time I looked at AW4s, it appeared that it used the same 2-bolt sensor in the same 10:00ish position that my AX15 used, so I would think some Jeeps don't need to do anything to run the AW4 successfully. I know the sensor moved down to about the 4:00 position on the 6 speed manuals, maybe it's installing an AW4 on those that is the issue? I'm not sure. @mrblaine, do you recall?

I do, 05-06 with the CPS over by the starter. Also why there is a CPS relocation kit for sale in the parts section. I won't do another one, I don't need that poo hanging around annoying me.

The swaps we've done all have used the "stand-alone" TCM but it should be noted they don't tie into the PCM. They use a few inputs and that's it. TPS, brake light sense, and some power and ground. About as stand alone as it gets.

This doesn't really matter. I mean it does eventually, but if it gets to the point it matters, it will show up on any ring and pinion ratio, and will not show up on a lower ring and pinion first. the lower gears, the smaller the teeth, but consequently, the lesser the amount of torque on the teeth due to leverage. It balances out to make most all the ring and pinion ratios about the same effective "strength." the short answer is that you don't want to use the skinny pedal too much with a rubicrawler or similar, regardless of what your axle ratio is. The axle ratio being whatever it is makes no real difference to the risk.

10.88-1 should be illegal with the auto. The chassis doesn't even torque over before it blows up both front shafts. Not stock shafts either.

I have yet to see a 35" tire anywhere close to 35", most are 33.5". Same for 33's, most are 31.5-31.7". If you are targeting so specifically to be at 2500 rpm, I would factor that in appropriately or you may not land where you want. Personally, I would absolutely want more than 2500 rpm on the highway. Even with more than 2500 downshifting will still be frequent for anything but a very minor grade.

I let that one go, too much work.

 

[Negreac]

Out of curiosity, why doesn't first gear in a manual transmission break every single time you leave from a stop, even with some spirited enthusiastic acceleration?

It has the smallest gear driving the biggest gear which has to violate the number of teeth in contact rule, so why don't they break? What would happen if you did the same bit of enthusiasm and tried to launch from 3rd or 4th gear? Your logic says those are the strongest or much stronger gears, so what would happen?

Ok well here is my general understand of why gear set get weaker as the ratios get higher (gearing gets deeper):

1. Smaller pinion head: For a given axle size a higher numerical gear ratio means the pinion gear must be smaller in diameter to accommodate fewer teeth.

2. Smaller thinner teeth: As the pinion head shrinks the gear teeth must also be made smaller and thinner to mesh correctly with the larger ring gear.

3. Reduced tooth contact area: The smaller teeth also have reduced overall tooth surface area in contact at any moment concentrating stress onto a smaller point of the gear teeth.

4. More stress cycles per tooth: The reduced number of teeth means its teeth endure more stress cycles over time. (i.e. a 5.11 will take ~25% more rotations of the pinion to travel the same distance and there are also 25% more pinion teeth on a 4.10 vs a 5.13 so for the same distance traveled each pinion tooth is seeing ~56.4% more load cycles)

Effectively just from a size perspective yes the smaller pinion has less strength but a compounding factor is the additional cycles, less area for the gear oil to absorb shock loads, and the less thermal mass meaning the heat cycles are fatiguing the material sooner.

I agree with @machoheadgames the same load is not being put on a 5.13 tooth as a 4.10 tooth as the mechanical advantage (distance from the ring/pinion contact gear to the pinion center axis) is less but it doesn't fully make up for a the aforementioned weaknesses of a smaller pinion in a dynamic system.

Please correct me if I am misunderstanding the tradeoffs in strength/durability when increasing axle gear ratios. I am always learning and this thread has already turned into the AP level classroom I had hoped it might.


Graphic showing reduced pinion sizes as gear ratio gets higher.

So I agree

 

[mrblaine]

Ok well here is my general understand of why gear set get weaker as the ratios get higher (gearing gets deeper):

1. Smaller pinion head: For a given axle size a higher numerical gear ratio means the pinion gear must be smaller in diameter to accommodate fewer teeth.

2. Smaller thinner teeth: As the pinion head shrinks the gear teeth must also be made smaller and thinner to mesh correctly with the larger ring gear.

3. Reduced tooth contact area: The smaller teeth also have reduced overall tooth surface area in contact at any moment concentrating stress onto a smaller point of the gear teeth.

4. More stress cycles per tooth: The reduced number of teeth means its teeth endure more stress cycles over time. (i.e. a 5.11 will take ~25% more rotations of the pinion to travel the same distance and there are also 25% more pinion teeth on a 4.10 vs a 5.13 so for the same distance traveled each pinion tooth is seeing ~56.4% more load cycles)

Effectively just from a size perspective yes the smaller pinion has less strength but a compounding factor is the additional cycles, less area for the gear oil to absorb shock loads, and the less thermal mass meaning the heat cycles are fatiguing the material sooner.

I agree with @machoheadgames the same load is not being put on a 5.13 tooth as a 4.10 tooth as the mechanical advantage (distance from the ring/pinion contact gear to the pinion center axis) is less but it doesn't fully make up for a the aforementioned weaknesses of a smaller pinion in a dynamic system.

Please correct me if I am misunderstanding the tradeoffs in strength/durability when increasing axle gear ratios. I am always learning and this thread has already turned into the AP level classroom I had hoped it might.


Graphic showing reduced pinion sizes as gear ratio gets higher.

View attachment 643071
So I agree

All you did was puke up the standard mythology. Answer my question about why the lowest gears in a manual transmission don't break.

 

[Negreac]

All you did was puke up the standard mythology. Answer my question about why the lowest gears in a manual transmission don't break.

"Out of curiosity, why doesn't first gear in a manual transmission break every single time you leave from a stop, even with some spirited enthusiastic acceleration?

It has the smallest gear driving the biggest gear which has to violate the number of teeth in contact rule, so why don't they break? What would happen if you did the same bit of enthusiasm and tried to launch from 3rd or 4th gear? Your logic says those are the strongest or much stronger gears, so what would happen?"

So if I understand the question here, you are asking me to explain why a 3rd gear would break over a 1st gear if the 3rd gear set is theoretically stronger since it runs a lower ratio?

This would assume you are keeping all other factors the same in regards to the size of the gear. This is not typically the case in a transmission unlike Axles. 1st gears are typically wider with deeper teeth than the following gears for this very reason. In addition to this the time spent in the subsequent gears is substantially longer than in 1st gear leading to accelerated, wear, fatigue and failure.

Example of manual gear box illustrating gear size differences

 

[Negreac]

One additional point to consider as well is that as you go up the gears the clutch loses it's mechanical advantage so it's ability to dampen the shock load also decreases.

 

[Ashim]

You have the 42RLE from factory. Below is your setup vs stock. Very nice configuration. Only thing I can think of that would make it even more adaptable is adding a Rubicrawler. This would add a higher 4-low (2.72:1) and a extremely 4-low (10.88:1). So you would have:

1. 4-H-L (RC engaged and NV241OR in 4 high) - 2.72:1 - 39.63 crawl ratio - 1.76mph @ 700rpm
2. 4-L (RC disengaged and NV241OR in 4 low) - 4.00:1 - 58.28 crawl ratio - 1.20mph @ 700rpm
3. 4-L-L (RC engaged and NV241OR in 4 low) - 10.88:1 - 158.51 crawl ratio - 0.44mph @ 700rpm

If you ever did this though I would just be careful with the skinny pedal in 4-lo-lo since with that much torque multiplication you could very well start breaking things downstream of your T-case. You already are already running a weaker ring/pinion than the factory 4.10 with the 5.13 (the deeper the gear the the less tooth contact and more susceptible to breakage) and you would be 272% of the torque multiplication of the factory 4-low 4.00:1

BTW the reason you are running 2500 RPM at 70mph instead of the ~2400 in the chart is probably because your 35s aren't actually 35s and closer to 34s if measured.

What is your experience with the OD and the shifting of the 42RLE with your setup? Have seen many complain about it but most with your gearing seem to be happy with how it reacts on freeway and around town.

View attachment 643069

I have no need for a Rubicrawler. 4L and first gear is low enough for going over rocks or providing engine braking on steep downhills. I have no need for a higher 2.72 ratio, I can go fast enough for the trails I do in 4L and 3rd gear. I can understand the need for higher speed in certain parts of the country, but what I normally run in OH, PA, WV, KY, TN I see no need for the 2.72 ratio.

 

[Negreac]

I have no need for a Rubicrawler. 4L and first gear is low enough for going over rocks or providing engine braking on steep downhills. I have no need for a higher 2.72 ratio, I can go fast enough for the trails I do in 4L and 3rd gear. I can understand the need for higher speed in certain parts of the country, but what I normally run in OH, PA, WV, KY, TN I see no need for the 2.72 ratio.

Makes sense, I know depending on the wheeling you do some prefer the 2:72 ratio over the 4:1 I believe I heard this specifically from those who do higher speed wheeling in the dunes and more open trails. I run mostly in MI so not a ton of natural slow obstacles here, mostly moderate speed trails and the dunes. Granted the ORV park I frequent does have some significant slower speed technical stuff.

 

[Negreac]

@mrblaine have I passed the exam or am I missing something all together with my understanding of gearing strength pertaining to axles and manual transmissions? Like I said, always learning and appreciate you taking the time to teach.

 

[mrblaine]

"Out of curiosity, why doesn't first gear in a manual transmission break every single time you leave from a stop, even with some spirited enthusiastic acceleration?

It has the smallest gear driving the biggest gear which has to violate the number of teeth in contact rule, so why don't they break? What would happen if you did the same bit of enthusiasm and tried to launch from 3rd or 4th gear? Your logic says those are the strongest or much stronger gears, so what would happen?"

So if I understand the question here, you are asking me to explain why a 3rd gear would break over a 1st gear if the 3rd gear set is theoretically stronger since it runs a lower ratio?

This would assume you are keeping all other factors the same in regards to the size of the gear. This is not typically the case in a transmission unlike Axles. 1st gears are typically wider with deeper teeth than the following gears for this very reason. In addition to this the time spent in the subsequent gears is substantially longer than in 1st gear leading to accelerated, wear, fatigue and failure.

Example of manual gear box illustrating gear size differences

View attachment 643096

Are you really going to make me point out the tiny gear turning the big gear?

 

[mrblaine]

@mrblaine have I passed the exam or am I missing something all together with my understanding of gearing strength pertaining to axles and manual transmissions? Like I said, always learning and appreciate you taking the time to teach.

You are missing that as the gears move lower in ratio, the leverage increases in favor of the gear for the same load. We don't put in lower gears to make it harder for the drivetrain to move the vehicle, we do it for the opposite, to increase the leverage to move the load easier.

You are also missing the conversations and the same mythology that has been on the internet at least for the last 22 years. If you ask most of the myth believers what gears to run, the common sentiment is to run 4.88 and avoid the tiny pinions on the 5.13's and 5.38's.

When I hopped on Jeeps Unlimited around 2001 or so, the lowest gears for the TJ were 4.56. Superior or similar introduced 4.88. The hand wringing and gnashing of teeth was exactly the same nearly verbatim. OMG, only one tooth in contact, tiny pinion, they will blow if you run them on stock tires, nobody should sell those, if you buy them yer gonna die.

Finally, my friend Jim McCabe, after watching the nonsense for a couple of years, put up a post asking if anyone had "FIRST HAND" knowledge of anyone blowing up a set. Oddly, no one raised their little crumb snatchers. He kept that post going for a very long time and still no takers. He tossed a set in his rig, wheeled it for a very long time with no issues. That isn't hard to believe given that the delicate little flower 4.88's of yore are now the gold standard of strength living up to the standards of the myth.

Anyone in business knows that the last thing you want to deal with is warranty, and spending time on the phone or answering emails from customers who have problems with your products. As such, if the lower ratios were the problem children the internet would have you believe, no one would sell them or sell them with any warranty provisions or barring that, only sell them with a OFF ROAD ONLY, YOU BREAK IT, YOU ARE YOUR OWN WARRANTY CENTER, BUY ANOTHER SET AND DON'T BOTHER US WITH YOUR BULLSHIT written across the box in bright red letters.

When I convinced Revolution to build the 5.13's and 5.38's in at least the thick cut versions so we didn't have to dump the factory lockers, I made sure that they ran the gear design past their engineers to make sure they would work and here we are many years later with 4 very successful gear options that have improved things for us.

 

[Negreac]

You are missing that as the gears move lower in ratio, the leverage increases in favor of the gear for the same load. We don't put in lower gears to make it harder for the drivetrain to move the vehicle, we do it for the opposite, to increase the leverage to move the load easier.

You are also missing the conversations and the same mythology that has been on the internet at least for the last 22 years. If you ask most of the myth believers what gears to run, the common sentiment is to run 4.88 and avoid the tiny pinions on the 5.13's and 5.38's.

When I hopped on Jeeps Unlimited around 2001 or so, the lowest gears for the TJ were 4.56. Superior or similar introduced 4.88. The hand wringing and gnashing of teeth was exactly the same nearly verbatim. OMG, only one tooth in contact, tiny pinion, they will blow if you run them on stock tires, nobody should sell those, if you buy them yer gonna die.

Finally, my friend Jim McCabe, after watching the nonsense for a couple of years, put up a post asking if anyone had "FIRST HAND" knowledge of anyone blowing up a set. Oddly, no one raised their little crumb snatchers. He kept that post going for a very long time and still no takers. He tossed a set in his rig, wheeled it for a very long time with no issues. That isn't hard to believe given that the delicate little flower 4.88's of yore are now the gold standard of strength living up to the standards of the myth.

Anyone in business knows that the last thing you want to deal with is warranty, and spending time on the phone or answering emails from customers who have problems with your products. As such, if the lower ratios were the problem children the internet would have you believe, no one would sell them or sell them with any warranty provisions or barring that, only sell them with a OFF ROAD ONLY, YOU BREAK IT, YOU ARE YOUR OWN WARRANTY CENTER, BUY ANOTHER SET AND DON'T BOTHER US WITH YOUR BULLSHIT written across the box in bright red letters.

When I convinced Revolution to build the 5.13's and 5.38's in at least the thick cut versions so we didn't have to dump the factory lockers, I made sure that they ran the gear design past their engineers to make sure they would work and here we are many years later with 4 very successful gear options that have improved things for us.

Ah so my flaw is in the statement:

"I agree with @machoheadgames the same load is not being put on a 5.13 tooth as a 4.10 tooth as the mechanical advantage (distance from the ring/pinion contact gear to the pinion center axis) is less but it doesn't fully make up for a the aforementioned weaknesses of a smaller pinion in a dynamic system."

The point is that it does make up for it, at least enough to not be of any concern. You have given me much to think about. I actually work for an OEM transmission/differential manufacturer. You have given me much to discuss with the engineering team this week. I suspect they will confirm exactly what you have pointed out and educate me further on the FEA and validation backing it up.

Thanks for administering the exam, will study harder next time.