Will I need to re-gear?

Starrs said:
I think it is safe to say based on the chart you have provided that factory rubicon gears with 42rle tranny is the same as stock essentially with a “33” that truly measures to 32.5. Is this correct? Just wanna make sure I’m reading this correct.
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I think that is what he is saying, but he’s also saying that the comparison with the other transmissions shows it was undergeared from the factor, so that 4.10 is undergeared.

It’s also teh reason Is as saying that if the Jeep engineers put 33’s on them from the factory, they would have probably gone with 4.88. It’s the numbers at 4.88 and the 42rle that fit nicely with the other transmission numbers.
 
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JMT said:
I think that is what he is saying, but he’s also saying that the comparison with the other transmissions shows it was undergeared from the factor, so that 4.10 is undergeared.

It’s also teh reason Is as saying that if the Jeep engineers put 33’s on them from the factory, they would have probably gone with 4.88. It’s the numbers at 4.88 and the 42rle that fit nicely with the other transmission numbers.
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Correct.
 
I'm not saying 3.73's are ideal for 33's just that I didn't notice much of a difference from the stock tire. Again this is mostly street driving on flat earth. I don't do much highway driving in it if I'm going on a road trip I'll take my wife's hybrid. And my off roading usually consists of low speed beach cruising.
 
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raycer12 said:
I'm not saying 3.73's are ideal for 33's just that I didn't notice much of a difference from the stock tire. Again this is mostly street driving on flat earth. I don't do much highway driving in it if I'm going on a road trip I'll take my wife's hybrid. And my off roading usually consists of low speed beach cruising.
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Now you're making excuses. Let's find a slow guy who never shifts out of first gear to show that none of this gearing talk matters at all. :)

I am working under the assumption that your Jeep and my Jeep should be a fully functional vehicle that can get out of its own way during normal daily driving. The interesting thing, if you follow along with my nonsense, is that everything I argue for in a good daily driven TJ also makes it better off road.
 
jjvw said:
Now you're making excuses. Let's find a slow guy who never shifts out of first gear to show that none of this gearing talk matters at all. :)

I am working under the assumption that your Jeep and my Jeep should be a fully functional vehicle that can get out of its own way during normal daily driving. The interesting thing, if you follow along with my nonsense, is that everything I argue for a good daily driver also makes it better off road.
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Ok so jeep undergeared these TJs from the factory is what your saying. The engineer team that designed these to run at those rpms undergeared them? If this is true there should be no harm to anybody’s vehicle driving it the way that jeep has it built...this is my stance with the 42rle and Rubicon gearing with 32.5” tires.
 
Starrs said:
Ok so jeep undergeared these TJs from the factory is what your saying. The engineer team that designed these to run at those rpms undergeared them? If this is true there should be no harm to anybody’s vehicle driving it the way that jeep has it built...this is my stance with the 42rle and Rubicon gearing with 32.5” tires.
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Using the 42rle as a baseline and knowing the numbers I posted earlier, would you be comfortable suggesting to people with all the other transmissions on stock jeeps that they could change to a numerically lower gear to better match what you have? What would be the benefit to that modification? Would these people be pleased with the change?

Yes, I am suggesting that Jeep (by design or not) undergeared the TJs for this transmission. It has been a known problem for almost 15 years.

If you want to argue that the engineers always made flawless decisions, then explain the OPDA design problem on the 05-06 model years that could ruin the engine. Is the NSG370 considered a good manual transmission? The early TJ cracking heads? Early TJ frame rot? The gas overflow problem on the 05-06? It took them 16 years to redesign the 4.0 exhaust manifold so they wouldn't crack. The hard door interior panels that crack in the same spot? The shovel?
 
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The reason the 42re comes attached to axles with the wrong gears is easy, $$$. It was probably supposed to have higher gears but the bean counters got involved and wouldn't allow yet another axle configuration. Then they did the same thing on the JK and the extra weight had the trans overheating and puking fluid out the dip sick. That poor transmission has a crazy low OD ratio. Don't get me wrong, having OD is a vast improvement over a 32re but it does need some extra help.

—
There must have been a time
when we could have said no.
 
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I have no dog in this fight, as I run 31.6" tires on my auto Rubicon. It's acceptable, but 4.56 would be better. There's a flat spot on the highway somewhere around 55-60 mph where I can tell the engine is struggling. Over that speed, it gets ok. Will I regear to 4.56 for 31.6" tires? I should, but won't. For that reason, I won't get 33" tires. Not with the 42RLE. If I did, you can bet, knowing how the Rubi performs with 32s, I'd regear to 4.88 at least with 33s.

Whether anyone else agrees, it only makes sense to me. Do what you want.
 
glwood said:
I have no dog in this fight, as I run 31.6" tires on my auto Rubicon. It's acceptable, but 4.56 would be better. There's a flat spot on the highway somewhere around 55-60 mph where I can tell the engine is struggling. Over that speed, it gets ok. Will I regear to 4.56 for 31.6" tires? I should, but won't. For that reason, I won't get 33" tires. Not with the 42RLE. If I did, you can bet, knowing how the Rubi performs with 32s, I'd regear to 4.88 at least with 33s.

Whether anyone else agrees, it only makes sense to me. Do what you want.
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There is no way I would drive a vehicle hat desperately needed a regear and was struggling to get up to speed. I promise you that lol. I guess I just like to go slower I’m not sure, but the way mine is setup is perfect for me. It’s not a money issue with gearing either I can assure anyone of that lol. I just honest to God feel no need for myself to do it when it is not needed for how my jeep is setup.
 
Performance wise, the 42rle is the worst transmission Jeep offered with it's axle gearing. We have known this for 15 years. The "charts" back this up.

If you haven't regeared your Jeep for larger tires, if you haven't driven a Jeep with larger tires that has been appropriately regeared, then you don't know what you are missing. It is as simple as that. You don't know.
 
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jjvw said:
Performance wise, the 42rle is the worst transmission Jeep offered with it's axle gearing. We have known this for 15 years. The "charts" back this up.

If you haven't regeared your Jeep for larger tires, if you haven't driven a Jeep with larger tires that has been appropriately regeared, then you don't know what you are missing. It is as simple as that. You don't know.
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This debate will never come to a close and frankly it’s all based on how the driver prefers to have his/her jeep drive. I may not know what I’m missing with deeper gears, but is it necessary to have deeper gears for me to have an adequately running jeep? Is my jeeps transmission going to explode since I don’t have 4.88 or 5.10 gears? Based on the charts my rpms are not to far off from stock....the way that the jeep engineers designed it hahaha I don’t know about you but I know what I have a degree in and it’s not engineering lol so I’m gonna leave the big calculated decisions to the engineers and just continue driving my jeep with factory gearing.
 
Starrs said:
...the way that the jeep engineers designed it hahaha I don’t know about you but I know what I have a degree in and it’s not engineering lol so I’m gonna leave the big calculated decisions to the engineers and just continue driving my jeep with factory gearing.
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Then you better stop modifying your jeep in ways that the engineers (or bean counters) never intended.

Until next time. We can solve this simple math problem again. :)
 
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The likely reason for the ridiculous tall od gear is for emissions. Slower turning engines produce lower emissions. Why the hell else would Jeep even consider the 3.07 as reasonable? GM started doing the same thing in the mid 80's, running 3.08's in their 4x4 pick ups. We re-geared bunches of those in the shop. Dudes would lift them and install 36's and wonder what the hell happened to the power. I can't recall the od in that trans but it was tall as well. For 35/36 we would recommend and install 5.57's in the GM 10 bolts diffs. People would freak over the number, until they drove it. Most guys thought 4.10 was as low as anyone would ever need, same as now.
 
I remember how surprised my dad was when I told him I was going to 4.88 for my 33s (5 speed). He is running 4.27 with 36s on his CJ. However, he also has a big v8, no over drive and far less weight to push. Now he gets it.
 
Starrs said:
Again.........it’s all a personal opinion. Nobody can tell you what you like better lol. You can’t make somebody like chocolate ice cream if they don’t. Myself and others love 33s with Rubicon gearing...33s and 3.73s might not be bad to some and some might hate them.
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Shoot. I thought the Rubis came with 4.10 standard..?
 
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