Gear ratios and bad advice

billiebob said:
Like I said, open yer mind. You just proved my point.
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Billiebob, your re-gear recommendations really don't make any sense at all. You and I have other things we like and I know you are not crazy, so please don't think I'm attacking you.

I am not a rock crawler and not even a serious offroader. I have a Rubicon/42RLE auto with 31.6" tires and a basic 2.5" lift. I had 4.10s and it sucked donkey balls driving the jeep on the highways. The engine lugs badly and is opertating pretty inefficiently because it is never in the right rpm range after 40-45mph. It is very obvious when you are driving and how the engine struggles to keep the vehicle at hwy speeds. And that is not lack of power, the engine can make gobs, but without the right gearing that power cannot get to the wheels. Please understand that these are actual facts and not opinions that you and I can debate.

You seem to always insist that everyone else recommends too deep a gearing. We don't. The recommendations that you see on this forum are pretty sound if you care about driving your vehicle at highway speeds comfortably. The recommendations are not based on increased crawl ratio. Please get that straight.

I really don't know anyone other than you that wants to drive at 60 in 4LO. But I know most everyone wants to drive at 65 on the highway in 2Hi without having to run the engine past 3000 rpm in one gear too low just because the engine (although capable) simply cannot develop enough power to the wheels efficiently to drive at 65 in the top gear.
 
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I know that my 4.7 stroker has gobs of power and with 4.10's and 33's with the 32RH it acts like a V8, too many RPM's on the highway in my situation causes excess heat though. The lack of overdrive and the 80% effeciency in the transmission increases the RPMs vs a manual. To each their own. Tim
 
I just want to say, this thread saved me in my regear. Going off what the video said I should have put 3.73 on my 3-speed 4.0 with 33s. It didn't sound right so I did more googling and this thread is one of the top Google hits. Went with 4.10 and I'm very happy with my choice. Huge upgrade from 3.07 with 33s!
 
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psrivats said:
Billiebob, your re-gear recommendations really don't make any sense at all. You and I have other things we like and I know you are not crazy, so please don't think I'm attacking you.

I am not a rock crawler and not even a serious offroader. I have a Rubicon/42RLE auto with 31.6" tires and a basic 2.5" lift. I had 4.10s and it sucked donkey balls driving the jeep on the highways. The engine lugs badly and is opertating pretty inefficiently because it is never the right rpm range after 40-45mph. It's is very obvious when you are driving and how the engine struggles to keep the vehicle at hey speeds. And that is not lack of power, the engine can make gobs, but without the right gearing if cannot get to the wheels. Please understand that these are actual facts and not opinions that you and I can debate.

You seem to always insist that everyone else recommends too deep a gearing. We don't. The recommendations that you see on this forum are pretty sound of you care about driving your vehicle at highway speeds comfortably. The recommendations are not based on increased crawl ratio. Please get that straight.
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I know, pretty sure that reply was not directed at you. I've always said the 42RLE was a special case with the 0.69 OD. And I've often backed the 4.88s for that combination. Or even deeper.

But with a clutch, 4.0L and 33s, I hate the 4.10s. I get crap mileage. I'd love 3.73s. My YJ with a carb, Peugeot tranny, 3.07s and 33s got 25mpg on the interstate.... in 4th gear. My TJR gets 20mpg if I keep it under 60mph in 6th. As to response, all I have to do is drop a gear or two if I need to pass or climb a grade.

And I don't criticize every low gearing recommendation. If the guy want 37s, or if he wants 33s on an SE or if he says, pure weekend off roader, I state there is little room for compromise and I go with the gearing everyone recommends. But I get attacked for saying 33s can work with taller gearing too. I don't go blindly willy nilly and say you must go deep with no consideration for the OPs stated use.

Honestly, you guys scare away anyone with a different opinion. The attack dogs come out. The desenters leave. And you end up with one opinion. I'm ready to join them.
 
billiebob said:
I know, pretty sure that reply was not directed at you. I've always said the 42RLE was a special case with the 0.69 OD. And I've often backed the 4.88s for that combination. Or even deeper.

But with a clutch, 4.0L and 33s, I hate the 4.10s. I get crap mileage. I'd love 3.73s. My YJ with a carb, Peugeot tranny, 3.07s and 33s got 25mpg on the interstate.... in 4th gear. My TJR gets 20mpg if I keep it under 60mph in 6th. As to response, all I have to do is drop a gear or two if I need to pass or climb a grade.

And I don't criticize every low gearing recommendation. If the guy want 37s, or if he wants 33s on an SE or if he says, pure weekend off roader, I state there is little room for compromise and I go with the gearing everyone recommends. But I get attacked for saying 33s can work with taller gearing too. I don't go blindly willy nilly and say you must go deep with no consideration for the OPs stated use.

Honestly, you guys scare away anyone with a different opinion. The attack dogs come out. The desenters leave. And you end up with one opinion. I'm ready to join them.
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I know that was not at me. But I feel that you are not fully understanding what we are saying.

Any Jeep set up well to handle the highway will be good off road as well (not counting driving at 60 in 4lo). The thing we are trying to explain to you is the inefficiency without proper gearing. Yes, even with 4.10s on my Jeep I can make it get into 3rd gear for passing. But it's really very apparent that the engine is struggling to do it. It's like having more than enough weight but not having the right fulcrum from your end in a see-saw. Without the deeper gearing, the 4.0 struggles in the same manner though it's plenty capable.

If you see the math behind the online calculators like grimjeepeeelr that people use, you'll really see the logic behind the recommendations. I'm going to PM a couple links for you to read it you are interested.

Also .. I don't think anyone is personally attacking you. Your Jeep use case is pretty different than most of us so it's feels bizzare to see your 3.73/33s recommendations for the 6spd. I personally know that it won't work for me if I had the 6spd
 
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I would still like to know if a desert racing trophy truck is using it's underdrive (be it RWD or 4WD) for 60mph, since that seems to be some kind of justification. Frankly I'm suspicious. What I do partially understand is that the reason trophy trucks are typically RWD has historically been the result of a compromise with the desire for reliability, speed, and suspension travel. Though, that compromise appears to be shifting as technology improves, allowing 4WD to better complete where it had not been able to in the past.

What this suggests is that we should not be comparing a multi purpose Wangler of any vintage to a specific purpose trophy truck. A slightly (barely) more reasonable comparison might be an Ultra 4 car. Are those guys using underdrive for 60mph across the desert? Even then, trying to make reasonable comparisons for our purposes feels silly.
 
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billiebob said:
The big one, if you are way too high, ie 3.07s, 33s, automatic or clutch, you might not have enough lift from a stop and damage the torque converter or shorten the clutch life. I had no problems with a clutch, not so sure about an automatic tho.

Honestly, lift from a stop is the only physical reason to regear.
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Again you will have to excuse my lack of knowledge of terminology. I’m trying to learn. Lift from stop - what does that mean?
 
Rob5589 said:
There should be a tag on the diff cover/s that will have the ratio imprinted. Something like, 3.07, 3.73, etc is what you'll be looking for. The 3spd auto with 33's and 3.73 should actually be very usable. If it is performing poorly it is very likely you have 3.07.
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I wouldn’t say that it performs poorly. Gas mileage is not great only about 14 mpg. Aside from that and the speedometer being off 5 mph that’s my only complaint
 
JMT said:
Great looking Jeep! Looks super clean. Congrats! Time now just to love Jeep life. With summer around, top down and doors off, nothing like it.

Good gas mileage will never be a TJ’s strong suit. It is what it is. Learn to punch penny’s and save for the next sheep mod, or gas!

To measure your true lift, look behind one of your front tires and find the big coil spring. You want to measure that spring. If there is a plastic spacer sitting on top of the spring, include that in the measurement. Don’t include the rubber coil spring isolator at the very top. Stock length is 12”, so anything above that is the amount of lift you have (e.g. 15” would mean you have 3” up front). Do the same in the rear, but stock is 8” and so anything over that is your lift in the rear.

Then report back. This will help determine what is the best tire size for your lift.

Then we can think about re-gearing for that tire size.

But for now just enjoy your new Jeep. There’s nothing else like it!
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Thank you so much!! I will look at these measurements tonight and report back. I don’t think it performs badly aside from the gas mileage being only about 14 mpg and the speedometer is off by 5 mph.
 
LittleTankTJ said:
I just want to say, this thread saved me in my regear. Going off what the video said I should have put 3.73 on my 3-speed 4.0 with 33s. It didn't sound right so I did more googling and this thread is one of the top Google hits. Went with 4.10 and I'm very happy with my choice. Huge upgrade from 3.07 with 33s!
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There needs to be a support group for those of us who bought a Jeep with 3.07s before we knew what that meant. I, too, ran 3.07s on 33s for 15 years and only swapped gears (axles) about two months ago. Hard to describe how much more fun it is to drive a properly geared rig.

374gatorgirl said:
Again you will have to excuse my lack of knowledge of terminology. I’m trying to learn. Lift from stop - what does that mean?
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They're referring to acceleration from a dead stop. If your gears are too numerically low for the size tire you're on, you will notice it most trying to accelerate from a stop light. The Jeep will struggle to get from 0 to 10 mph or so. If you've ever ridden a multi-speed bike and wound up coming to a stop without downshifting, think about what it was like to get going again without shifting into a lower gear. That's about how a Jeep with 3.07 gears and 33 inch tires (for instance) drives away from a stop.
 
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jjvw said:
I would still like to know if a desert racing trophy truck is using it's underdrive (be it RWD or 4WD) for 60mph, since that seems to be some kind of justification. Frankly I'm suspicious. What I do partially understand is that the reason trophy trucks are typically RWD has historically been the result of a compromise with the desire for reliability, speed, and suspension travel. Though, that compromise appears to be shifting as technology improves, allowing 4WD to better complete where it had not been able to in the past.

What this suggests is that we should not be comparing a multi purpose Wangler of any vintage to a specific purpose trophy truck. A slightly (barely) more reasonable comparison might be an Ultra 4 car. Are those guys using underdrive for 60mph across the desert? Even then, trying to make reasonable comparisons for our purposes feels silly.
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It is a delicate balance to pick and choose the important attributes of other disciplines and use them to our advantage when comparing different mods to find the value in doing something a certain way.

I can find out and will if it matters exactly what trophy trucks do for gearing. But, by and large, very little of what they do with regard to the drivetrain will carry over. I did find out. They run 6-800 hp motors with Turbo 400 transmissions and sub 4.XX gearing in the axle. Just about zero that carries over to the TJ and its gearing requirements.

The first glaring disparity is horsepower. They have enough to pull any gear set that they want for the most part. They don't run a two speed case because they are 2wd as you noted. The Ultra 4 classes that have been competing with the TT folks over the last several years are causing the switch to 4wd and the complexity thereof. The silt beds have been an issue for the TT folk. The Ultra 4 rigs zipping through them like nothing have opened some eyes.

The second glaring disparity is they run automatic transmissions. Bringing a TT into a gearing discussion for the TJ is about the same as using their use of high dollar bypass shocks and coilovers on trailing arms with a greater than 1-1 motion ratio as what we need for suspension under a TJ. It is a silly comparison.
 
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374gatorgirl said:
I wouldn’t say that it performs poorly. Gas mileage is not great only about 14 mpg. Aside from that and the speedometer being off 5 mph that’s my only complaint
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A Jeep on 33's, honestly, 14 isn't horrible. There are plenty of "what's your mpg" posts. Search for them and compare. You may not feel as bad about that 14 mpg.
 
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BlackJeep said:
There needs to be a support group for those of us who bought a Jeep with 3.07s before we knew what that meant. I, too, ran 3.07s on 33s for 15 years and only swapped gears (axles) about two months ago. Hard to describe how much more fun it is to drive a properly geared rig.



They're referring to acceleration from a dead stop. If your gears are too numerically low for the size tire you're on, you will notice it most trying to accelerate from a stop light. The Jeep will struggle to get from 0 to 10 mph or so. If you've ever ridden a multi-speed bike and wound up coming to a stop without downshifting, think about what it was like to get going again without shifting into a lower gear. That's about how a Jeep with 3.07 gears and 33 inch tires (for instance) drives away from a stop.
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Thank you so much for your response and tips. I thought that’s what they meant but wanted to make sure my common sense was right. I really don’t have any struggle accelerating from a stop. So I guess that’s a good thing. I don’t gun it or anything but I definitely don’t notice it lagging at all.
 
374gatorgirl said:
Thank you so much for your response and tips. I thought that’s what they meant but wanted to make sure my common sense was right. I really don’t have any struggle accelerating from a stop. So I guess that’s a good thing. I don’t gun it or anything but I definitely don’t notice it lagging at all.
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I realize it doesn’t feel to you like you have trouble, but if you had the opportunity to drive your rig or someone else’s with the same setup but proper gearing you’d feel a big difference. As @BlackJeep noted.

Also, 14mpg is pretty normal. Most of us probably get in the 13’s
 
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billiebob said:
Got to chime in. I drove 33s & 3.07s for 10 years. But not thru the automatic.

First with what you have how does it perform in 4LO on a gravel road. For me this was why I never regeared. It ran like a Mustang in 4LO and would hit 60mph.

Second in 2HI on the highway how is it? I assume you will often shift to second gear to pass, climb a grade, run into a headwind. If you can handle that, great.

Third, and this is the deciding factor to regear, from a stop, how does it perform. I'm thinking it has trouble getting enough lift from a stop. With mine and the 5 speed, I noticed the difference but with the automatic, if it struggles it is hard on the torque converter too.

Where to regear too....... I disagree with most advice you will see here. If your TJ is for the extremes of the sport yes you want 4.10s or deeper gears. But if this is a Wrangler to enjoy places only Wranglers go.... ie beaches, forestry roads, back country trails, even 4.10s are too deep.

I have a Rubicon with 4.10s AND an overdrive 6th gear. You do not have overdrive, 3rd is direct like my 5th gear. And I wish I had the 3.73 ratio with my 33s. 3.73s with your 3 speed automatic is similar to 4.10s thru an overdrive standard. I will get shot to hell for being honest but unless you want to climb that waterfall..... go 3.73s or taller.
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Is driving in 2Hi recommended on the highway? Again, showing my lacking knowledge here.
 
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