Need help shopping for new gears

I wonder why every time there is a thread on octane, lift geometry or regearing before it's over someone is dragging someone's fat alcoholic mother into the conversation.

I'm sorry but I think most of the time the person that is quoting all the statistics or math or whatever has the least experience of actually doing it... And I think that's just to support the fact that they really don't know what they're talkin about..

anyway I'm not trying to hurt anybody's feelings and I may be as wrong as I can be so accept my apologies if I am... And I don't think I'm the Forum police...but all you have to do is take the Jeep down to the shop and tell them to put the right ratio of gears for the tire size in it and write a check.

It's more important to deal with a competent shop than it is to know all the statistical probability.

Anyway that's my rant... I'll shut up.

I'd be careful with that idea. The "math or statistics or whatever" is what allows people to draw their own conclusions on a topic versus blindly accepting what others on a forum say. At least in my opinion, forums should be a place where people can have discussions over what conclusions they have come to. Having some debate about how people have come to those conclusions and what assumptions they used to do so is perfectly healthy. Everyone has had a different personal experience, so it is very hard to rely just on that.

I'll try to give an example. The shop that is doing my frame swap loves metalcloak fenders. At one point, the owner at this shop told me the best way to fit my 35's was to get metalcloaks. I could have blindly taken that advice due to the fact that the owner has been in the Jeep business since before TJ's even came out, or I could do a little critical thinking, some reading, and maybe a little math to come to my own conclusions. I've decided that metalcloaks would do me no good, contrary to what the guy with tons of experience told me.

At least in the scope of this thread, the reason why so many of these discussions devolve into insults is because people are condescending when trying to show their point. It is just like politics, there is no discussion, just people claiming they are 100% right.
 
Exactly. When I had my 3.73's and 6-speed with 33's I often used to run in 5th around 3000rpm just so I could keep speed on the hills around here. 6th was non-existent. The engine loved it and my temps never went over 210. Now that I'm on 4.56's I'm at 2850rpm in 6th at 70mph and the engine loves it, I have power, my top speed is lower, but I don't know what it is because I'm not interested in running my Jeep over 75mph. If I'm going to go that fast I'll just drive my father-in-laws C6.
Man I feel the same way.
 
I'd be careful with that idea. The "math or statistics or whatever" is what allows people to draw their own conclusions on a topic versus blindly accepting what others on a forum say. At least in my opinion, forums should be a place where people can have discussions over what conclusions they have come to. Having some debate about how people have come to those conclusions and what assumptions they used to do so is perfectly healthy. Everyone has had a different personal experience, so it is very hard to rely just on that.

I'll try to give an example. The shop that is doing my frame swap loves metalcloak fenders. At one point, the owner at this shop told me the best way to fit my 35's was to get metalcloaks. I could have blindly taken that advice due to the fact that the owner has been in the Jeep business since before TJ's even came out, or I could do a little critical thinking, some reading, and maybe a little math to come to my own conclusions. I've decided that metalcloaks would do me no good, contrary to what the guy with tons of experience told me.

At least in the scope of this thread, the reason why so many of these discussions devolve into insults is because people are condescending when trying to show their point. It is just like politics, there is no discussion, just people claiming they are 100% right.
I'm not telling anyone not to do their homework...I have a thread right now trying to find out more about the mechanics of the front ends of these things just so that I understand before I let anybody touch my Jeep.


But when people start trying to shove it down other people's throat that's when it's going too far...typically your best position is both the science and educated side of things and the practical side combined.

Most people that apply their trade that way tend to be pretty dangerous.... And I mean that in a good way.
 
I'm not telling anyone not to do their homework...I have a thread right now trying to find out more about the mechanics of the front ends of these things just so that I understand before I let anybody touch my Jeep.


But when people start trying to shove it down other people's throat that's when it's going too far...typically your best position is both the science and educated side of things and the practical side combined.

Most people that apply their trade that way tend to be pretty dangerous.... And I mean that in a good way.

How can you quantify personal experiences? I could argue that 3.07's are great with my 40's on stock axles and 2.5" of lift. Most people only have long term experiences in 1 Jeep with 1 type of setup. Explaining the math is what disproves the dumb setup described above. Everybody has different experiences based on where they drive, how they drive, what they expect, etc... You can't have different numbers if you do the math right. You just have to make sure the math you're doing is applicable in the overall grand scheme of things.

If you are trying to pitch your new company to a set of investors, you don't tell them how you view your company personally, you tell them the numbers and allow them to make their own decisions. Same thing goes for gearing Jeeps.

Obviously math isn't the only part of a good argument, personal experience definitely matters. But when trying to explain why you made a certain decision, you might have to "shove the math" to get people to listen.
 
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That's a hundred percent correct... But you don't argue with them until everyone is blue in the face and about to kill each other.

People do make decisions based on facts but they also use their personal judgment and emotions.

I'm just pointing out that the extremity of these arguments is beyond beneficial.

it's also a lot more powerful to demonstrate what actually happens in terms of RPM and engine speed after re gear than what the statistics say will happen.

One thing people don't realize is a set of mud terrain tires will lose 1 to 2 inches of diameter in the course of their lifespan.

There just aren't any absolutes unless everything is equal on each vehicle.
 
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My understanding (and perhaps someone more knowledgable like @mrblaine can comment on this as to whether I'm wrong or not) was that Chrysler used the 42RLE for the TJ because it was a transmission they were already using in many of their other FWD vehicles. It was never a clean sheet design or anything, specifically meant for the TJ.

In addition, I've read things here and there in the past that mentioned the ridiculous overdrive ratio and constant low RPMs it keeps you at were a result of Chrysler trying to meet emission standards.

Again, I don't know if that's accurate, it's just what I've read.

I really don't care who says what, a 4.0s optimal cruising RPM on the highway is certainly not under 2000 RPM. I mean sure... if you want to live with that and think that's acceptable, then by all means, be my guest. I think the majority will agree that it's mind numbing.

So yes, while everyone is entitled to their "opinion" on the matter, I think that the majority of people are going to agree that keeping the engine at higher RPMs (above 2000) is going to be better.

In addition, I've heard from @Jerry Bransford and others that consistently keeping the engine at low RPMs thinking that you're "saving the engine" is actually bad for the engine. I'm not the expert on this matter, but it makes sense from things I've read over the years.

If optimal for you is over 2K, that's great, it's your Jeep.

All internal combustion engines are cleaner at higher RPM. Some exotics even bypass the cats at high RPM. So the emissions thing seems rather unlikely.

Simply stating high RPM is better for economy means nothing, Chrysler had the fuel curves when the programmed the transmission. The 42RLE is programmed to perform the entire EPA economy test below 2000rpm. Chrysler could have picked any RPM to shift, they chose between 1200 and 1800 to maximize economy. If you want throttle response or the ability to climb a hill without downshifting it's a terrible idea, I've never said otherwise.

As for engine wear and RPM, if every single automatic transmission built in the last 60 years shifting to keep RPMs at their lowest possible levels doesn't convince you that's important then nothing will. Detonation can cause problems under severe lugging but otherwise once the engine is up to temperature the increased combustion temps caused by lugging cause no problems. Anybody ever get a recommendation to put an EGT gauge on a stock 4.0? Nope.

If anybody is bothered by the discussion, tune out.
 
The TJ's gearing obviously differs for many different transmissions. Knowing what gears to get is dependent solely on where the power-band is and whether you can use all your gears. BTW, the powerband is around 2500-2700rpm. If you're on a hill in a gear and you drop below that, you won't gain speed on that hill.

When I did the math I used 3.73's and stock tires as a standard because it met the above criteria. If I had used 3.07 I would have gotten different results and the gears I got would have sucked!

With 3.73's and moving to 33's I found 4.27 would return my rig to good performance. There is no 4.27 so I could go with 4.10 and be undergeared or 4.56 and be overgeared. If I went with 35's optimal gearing I found was 4.71. So, what is a man to do? Easy, pick 4.56 and if I run 33's I'll be overgeared. So what. I have power. If I run 35's. So what. I'll be only slightly undergeared. I'll still have power.

Some people have dumpy setups for one reason or another; enter the 3.07 gears and the 42rle tranny. They need to follow the same criteria above; where is the power band (2500-2700rpm) and can I use all my gears with the gear ratio I use. In some cases there may be two possible options. Weigh your primary uses of the Jeep and go for it.
 
Respectfully, no.
If optimal for you is over 2K, that's great, it's your Jeep.

All internal combustion engines are cleaner at higher RPM. Some exotics even bypass the cats at high RPM. So the emissions thing seems rather unlikely.

Simply stating high RPM is better for economy means nothing, Chrysler had the fuel curves when the programmed the transmission. The 42RLE is programmed to perform the entire EPA economy test below 2000rpm. Chrysler could have picked any RPM to shift, they chose between 1200 and 1800 to maximize economy. If you want throttle response or the ability to climb a hill without downshifting it's a terrible idea, I've never said otherwise.

As for engine wear and RPM, if every single automatic transmission built in the last 60 years shifting to keep RPMs at their lowest possible levels doesn't convince you that's important then nothing will. Detonation can cause problems under severe lugging but otherwise once the engine is up to temperature the increased combustion temps caused by lugging cause no problems. Anybody ever get a recommendation to put an EGT gauge on a stock 4.0? Nope.

If anybody is bothered by the discussion, tune out.
Are you going to disagree that bigger tires require higher rpms to produce the same performance? And are you doing to disagree that mounting larger tires without lowering the axle gear ratio will reduce the engine rpms below what the factory set them at for the original smaller size tires? One thing I have noticed is that you and I definitely march to the beat of a way different kind of drummer.
 
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If optimal for you is over 2K, that's great, it's your Jeep.

All internal combustion engines are cleaner at higher RPM. Some exotics even bypass the cats at high RPM. So the emissions thing seems rather unlikely.

Simply stating high RPM is better for economy means nothing, Chrysler had the fuel curves when the programmed the transmission. The 42RLE is programmed to perform the entire EPA economy test below 2000rpm. Chrysler could have picked any RPM to shift, they chose between 1200 and 1800 to maximize economy. If you want throttle response or the ability to climb a hill without downshifting it's a terrible idea, I've never said otherwise.

As for engine wear and RPM, if every single automatic transmission built in the last 60 years shifting to keep RPMs at their lowest possible levels doesn't convince you that's important then nothing will. Detonation can cause problems under severe lugging but otherwise once the engine is up to temperature the increased combustion temps caused by lugging cause no problems. Anybody ever get a recommendation to put an EGT gauge on a stock 4.0? Nope.

If anybody is bothered by the discussion, tune out.

Give me the reasoning behind why low RPM is good for longevity. You can't assume Chrysler programmed transmissions that way because of longevity without proving it. Which specific component of an engine is going to fail faster because of sustained 3000 rpm drives and why? Based on everything I know about engines, I can't see a reason, but I am more than willing to be wrong. I don't claim to know everything.
 
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Automatic transmissions up-shift to their top gear, they never "hold" a lower gear or allow the engine to gently spin up to a higher RPM. Under light loads automatic transmissions all reduce RPM as much as they possibly can. The 42RLE even disconnects the torque converter downhill off throttle letting the engine go to idle instead of letting it spin up any higher than necessary.
I have never encountered any situation with a 42 where it goes into neutral while in gear. If you have one doing that, something is wrong with it or something is wrong with the rest of them I have driven.
 
I have never encountered any situation with a 42 where it goes into neutral while in gear. If you have one doing that, something is wrong with it or something is wrong with the rest of them I have driven.
Disconnect torque converter is what I said, probably should have said unlock. Roll back on the gas and the torque converter will re-lock.
 
Are you going to disagree that bigger tires require higher rpms? And are you doing to disagree that mounting larger tires without lowering the axle gear ratio will reduce the engine rpms below what the factory set them at for the original smaller size tires? One thing I have noticed is that you and I definitely march to the beat of a way different kind of drummer.
Nope, I agree with all three points. Although I would say that bigger tires require more power which sometimes you can make at lower RPM but people often just don't like to. My opinion is that turning off the O/D and using the first three gears on the 42RLE is a bit like putting 5 and up gears without the downside of the high driveshaft speed. That's really it, kinda a cheap alternative solution. Doesn't hurt that the first three gears on the 42RLE match the 32RH. And yes, I know they shift a little different.
 
Give me the reasoning behind why low RPM is good for longevity.

The crank wears every rotation. Lower RPM means fewer rotations per mile driven. It could mean higher wear if the loads are higher. I am not suggesting that either of us know the answer. What I do know for sure it that a Chrysler engineer that does know about engine wear programmed my Jeep to run on the freeway at about 2100rpm and not 3500rpm. Even large generators reduce RPM under light or no load conditions to reduce engine wear. If you can generate the power at lower RPM every company that designs and builds internal combustion engines takes advantage of it. Nobody just lets the engine spin away needlessly at higher RPM.
 
If there was a way to wire the system so that the default for the 42RLE is OD "off" with switch turning OD "on" instead, then using gears 1-3 would be a viable alternative. It would not be unlike the C6 with Gearvendor overdrive I had in a Ford diesel pickup I used to have.

It was too much of a hassle for me to manually turn OD "off" in my LJ every time I shifted into Drive so I re-geared to 5.38 so I could do with my transmission as Ron Popiel pitches in his Infomercials, "Set it and Forget it."

If someone doesn't like my decision-making process or my solution they don't need to drive my jeep. ;)
 
The crank wears every rotation. Lower RPM means fewer rotations per mile driven. It could mean higher wear if the loads are higher. I am not suggesting that either of us know the answer. What I do know for sure it that a Chrysler engineer that does know about engine wear programmed my Jeep to run on the freeway at about 2100rpm and not 3500rpm. Even large generators reduce RPM under light or no load conditions to reduce engine wear. If you can generate the power at lower RPM every company that designs and builds internal combustion engines takes advantage of it. Nobody just lets the engine spin away needlessly at higher RPM.

The crank wears every rotation? Lets do some math to see about that.

My engine has around 225,000 miles. Assuming an average speed of 60 (which is very high) and an average rpm of 2500, that means my engine has rotated 562,500,000 times. In reality that number is much higher. If my crank was wearing even the slightest amount during each revolution then it would have been garbage years and years ago. If my crankshaft is not outside of the very small, thousandths of an inch, tolerance after an estimated 562,500,000 revolutions, then it is not wearing at all.

Do car manufacturers really try to produce power at low rpm? What about the S2000 that revs to 9000 rpm? Why didn't they just put a lower revving engine that produces the same power in there? Why don't people criticize manufacturers that have higher revving engines for their reliability? This point is not right either.


I'm still ready to be proved wrong.
 
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I hope everybody understands I was just trying to get people to think a bit before they spend their money on gears. I have a great deal of respect for all the opinions expressed.

I thought engines wore out based on how much they spun, but if that's not the case I'm wrong, I don't know the answer. A guy that rebuilt my ford six at H&H Flatheads told me, when I asked about the longevity of the model A engine, that they lasted a long time because they don't rev high. He told me older engines that tick away at lower rpm last forever compared to modern engines. He could be wrong, I could be wrong, it's not big deal.

I had an S2000, man that thing had a flat torque curve. Pretty even from 2500-9000rpm. So much fun.
 
The crank wears every rotation. Lower RPM means fewer rotations per mile driven. It could mean higher wear if the loads are higher. I am not suggesting that either of us know the answer. What I do know for sure it that a Chrysler engineer that does know about engine wear programmed my Jeep to run on the freeway at about 2100rpm and not 3500rpm. Even large generators reduce RPM under light or no load conditions to reduce engine wear. If you can generate the power at lower RPM every company that designs and builds internal combustion engines takes advantage of it. Nobody just lets the engine spin away needlessly at higher RPM.
That is a point oft overlooked by most in gear discussions and shouldn't be.

If you use the Grimm Jeeper website and plug in a stock TJ 4.0 32RH with the factory 28" tires and the very common 3.73 axle ratio, you will quickly see that Jeep has no issue running the rig at higher RPM that what most consider prudent or even favorable.

The two attachments show the RPM at 70 and 80 mph. Maybe Jeep knows something most don't.

32RH70.PNG


32RH80.PNG
 
The crank wears every rotation? Lets do some math to see about that.

My engine has around 225,000 miles. Assuming an average speed of 60 (which is very high) and an average rpm of 2500, that means my engine has rotated 562,500,000 times. In reality that number is much higher. If my crank was wearing even the slightest amount during each revolution then it would have been garbage years and years ago. If my crankshaft is not outside of the very small, thousandths of an inch, tolerance after an estimated 562,500,000 revolutions, then it is not wearing at all.

Do car manufacturers really try to produce power at low rpm? What about the S2000 that revs to 9000 rpm? Why didn't they just put a lower revving engine that produces the same power in there? Why don't people criticize manufacturers that have higher revving engines for their reliability? This point is not right either.


I'm still ready to be proved wrong.
The crank can not actually wear much at all or you will not have any oil pressure. What stops the crank from wearing is the oil film that all the crank and piston rod bearings ride on. Without that pressurized oil film, you wouldn't get very far at all because wear would enter into it.
 
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If there was a way to wire the system so that the default for the 42RLE is OD "off" with switch turning OD "on" instead, then using gears 1-3 would be a viable alternative. It would not be unlike the C6 with Gearvendor overdrive I had in a Ford diesel pickup I used to have.

It was too much of a hassle for me to manually turn OD "off" in my LJ every time I shifted into Drive so I re-geared to 5.38 so I could do with my transmission as Ron Popiel pitches in his Infomercials, "Set it and Forget it."

If someone doesn't like my decision-making process or my solution they don't need to drive my jeep. ;)
I'm geared to 4.88 with factory take off JK tires. I hit the OD off switch every time I start it. It is just a matter of making it a habit to be viable.
 
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