Madness, your 4.0L will window the Block with all them screaming Highway RPM's. 5.38's is insane. Just run down a gear.
Don't say you weren't warned.
Gear ratios and bad advice
- Thread starter Brantley
- Start date
Don't say you weren't warned.
Yep. Still waiting!Madness, your 4.0L will window the Block with all them screaming Highway RPM's. 5.38's is insane. Just run down a gear.
Don't say you weren't warned.
Your 4.0L will only blow up with 5.38's if you are running full synthetic high mileage oil and have not replaced your RMS and the NV3550. But, if you have changed the RMS and are running regular oil and 35's with 5.38's and a 42RLE you will be good WITH an AUX trans cooler. Again, with the 32RH and semi-synthetic and stop leak with 33's and 4.88's that's OK. IF running the AX-15 and 37's with 3.73's you can just run 3rd gear on the interstate if you add Lucas stabilizer before every trip UP to 94 MPH.Yep. Still waiting!
I hope that clears some things up.
It's not even Tuesday.
If I regeared my rearend to 4.56 the overall ratios aren't significantly different and almost identical between 5th and sixth gear at 3.73x1 and 4.56x.83. At 3.73 vs 3.78 overall ratio the engine would not know the difference. So if I want to feel the performance of regearing to that I can simply rev higher and not shift into OD on the highway. The most gearing change is in the low range so I could see the love for it off road. On road the low gears are already almost too low already. If I'm pointed somewhat down hill I'll take off in second. Shift at 2500-3000.
I run my mini at 3,000 all the time to keep boast up on the supercharger. I try to stay below 7000 rpm or I'm going too fast. So the RPMs on these tractors are nothing.
So like I said with my configuration, I'm start with, lift, and tires <35", with armor (tummy tuck) and transfercase first, then look at gearing on breakage or when adding lockers. Optimizing money expenditures and fun.
If I had a Rubicon I'd start with armor tummy tuck. I might regear it if it was an automatic. If I had a 4 cylinder with 3.07 gears and bigger tires, I'd regear.
Each Jeeps starting point and use varies enough there almost needs to be an advice questionnaire or flowchart.
I run my mini at 3,000 all the time to keep boast up on the supercharger. I try to stay below 7000 rpm or I'm going too fast. So the RPMs on these tractors are nothing.
So like I said with my configuration, I'm start with, lift, and tires <35", with armor (tummy tuck) and transfercase first, then look at gearing on breakage or when adding lockers. Optimizing money expenditures and fun.
If I had a Rubicon I'd start with armor tummy tuck. I might regear it if it was an automatic. If I had a 4 cylinder with 3.07 gears and bigger tires, I'd regear.
Each Jeeps starting point and use varies enough there almost needs to be an advice questionnaire or flowchart.
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When it comes to power/torque delivery and the way the ratios land, I tend to agree. But it also seems to come with an increased risk of ending up with difficult-to-solve vibration issues due to the crazy driveshaft speeds. I recently learned on a phone call to Tom Wood's driveshafts that the selection of driveshaft balancing machines isn't a big market, they have mostly all come from the same company for decades, and they only balance up to 3300rpm. 35's and 5.13's will be at 4100rpm at 75mph, and since centrifugal force increases with the square of velocity, they may not be able to detect an amount of imbalance that fully reveals itself at 75mph.
4 cyl Jeeps came with 4.10 factory. Stump puller woodsman gears. That's why the 4 cyl is so sought after.
The point that you're missing is it's not an exact step-shift of all the transmission gears when you regear. 4.56 does not just kick all your gears an identical amount lower. It is a proportion, but it's not like gears 2,3,4,5,6 with 4.56 are now the same as 1,2,3,4,5 with 3.73 used to be. You have effectively lowered them all with 4.56 but the new 2nd gear does not equal the old 1st gear. Same for all the other gears. What does happen with 4.56 though is that it makes every gear more enjoyable across the range during acceleration. Also, you have it the close to the best of any stock jeep with 3.73 and the 6 speed. Your setup is way more manageable than many others.
I have a nsg370 5.13 gears and can cruise comfortably at 85 mph. It’s still not topped out...
If you look at the numbers, 5.13 pushing 35s is a lower rpm than 4.88 pushing 33s.
without using a calculator cause I have the Dumb currently. I believe the difference between 4.88 and 5.13 is like 5%. Again, madness. So low and crawly.
Yeah I get all the gearing differences as it goes through gears. That's why I mentioned looking at how the differential change is affecting all of them so I don't get stuck shifting more often in traffic.
I'd look at it differently with a different transmission. And differently for strickly offroad versus street, or if I lived somewhere else, etc, etc. If I bought another TJ with a different transmission I'd set it up differently depending on what I was trying to do. Obviously most here want as much of a boost in the low gears to compensate off road as on.
I'm looking at it differently. By upgrading my transfer case first I can get off road now and keep my on road driving manageable through the stick. Then upgrade axles with minor jump in gears as I go while staying close to the original engine RPM across typical on road conditions. It's just solving a similar problem from a different angle. Some here do all at once. Most online upgrade to what some says then upgrade again later.
With 35" tires, I'd likely settle on 4.10 differential gearing for on road flat Nebraska and let a 5:1 atlas transfer case pick up the off road stuff. That allows more crawl off road and just enough on road for tire size compensation. The higher gears on road the lower I'd want my transfer case.
It seems like for on road trying to keep each transmission/differential gear combination in the 2500-3000 range would optimize out the 4.0l engine curves and felt response.
With automatics and other transmissions, the choices are actually easier because it's the only variable to control. The computer picks the transmission gear for you. I'd find the typical rpm range of each stock gear before shifting and match the differential gearing to replicate it with larger tires. They are likely holding the shift points to keep the engine in a range that gives the best torque and efficiency.
For an automatic, I'd pick my tire upgrade size, then drive around on stock tires watching the tack and speedo and feeling the shift points, then try to calculate similar engine rpms through my transmission by varying the differential gearing. Hopefully, find a new ratio that approximates stock. Then if I wanted more off road without a transfer case upgrade go up a gear. If I planned on a transfer case upgrade I'd keep the differential gearing to what I estimated and adjust the off road with the case. (You know some poor guy at Jeep ran engine, transmission, and shift point optimization calculations for years to make sure we got the awesome 17/19mpg we get)
It's all a process. Like they said in the thread anyone who's done it a while will have general guidelines in their head and be able to recommend what works for which Jeep doing what thing. They use decades of experience. But the internet sucks, and typically buries good advice in enough BS until people pick something popular and/or has a random shop install it for them.
When I get to that step, I'm going to learn about building axles and installing gears and lockers. Because, that's the fun stuff. I'm sure the internet is full of random opinions on those too.
I do like this site because of the technical knowledge available. It works as an internet filter for me. But I've had enough experts screw stuff up for me that I'm not trusting by nature. And Blaine doesn't have a shop down the street. So I'll do it and if I mess up at least I saved labor costs over paying someone else to screw it up for me.
I like the way the Jeep handles and performs now, so I'm picking the best route to end up back at this street performance and gain off road. But focus on off road first. Differentials first won't do that. It's probably why I see so many people regear more than once.
I'd look at it differently with a different transmission. And differently for strickly offroad versus street, or if I lived somewhere else, etc, etc. If I bought another TJ with a different transmission I'd set it up differently depending on what I was trying to do. Obviously most here want as much of a boost in the low gears to compensate off road as on.
I'm looking at it differently. By upgrading my transfer case first I can get off road now and keep my on road driving manageable through the stick. Then upgrade axles with minor jump in gears as I go while staying close to the original engine RPM across typical on road conditions. It's just solving a similar problem from a different angle. Some here do all at once. Most online upgrade to what some says then upgrade again later.
With 35" tires, I'd likely settle on 4.10 differential gearing for on road flat Nebraska and let a 5:1 atlas transfer case pick up the off road stuff. That allows more crawl off road and just enough on road for tire size compensation. The higher gears on road the lower I'd want my transfer case.
It seems like for on road trying to keep each transmission/differential gear combination in the 2500-3000 range would optimize out the 4.0l engine curves and felt response.
With automatics and other transmissions, the choices are actually easier because it's the only variable to control. The computer picks the transmission gear for you. I'd find the typical rpm range of each stock gear before shifting and match the differential gearing to replicate it with larger tires. They are likely holding the shift points to keep the engine in a range that gives the best torque and efficiency.
For an automatic, I'd pick my tire upgrade size, then drive around on stock tires watching the tack and speedo and feeling the shift points, then try to calculate similar engine rpms through my transmission by varying the differential gearing. Hopefully, find a new ratio that approximates stock. Then if I wanted more off road without a transfer case upgrade go up a gear. If I planned on a transfer case upgrade I'd keep the differential gearing to what I estimated and adjust the off road with the case. (You know some poor guy at Jeep ran engine, transmission, and shift point optimization calculations for years to make sure we got the awesome 17/19mpg we get)
It's all a process. Like they said in the thread anyone who's done it a while will have general guidelines in their head and be able to recommend what works for which Jeep doing what thing. They use decades of experience. But the internet sucks, and typically buries good advice in enough BS until people pick something popular and/or has a random shop install it for them.
When I get to that step, I'm going to learn about building axles and installing gears and lockers. Because, that's the fun stuff. I'm sure the internet is full of random opinions on those too.
I do like this site because of the technical knowledge available. It works as an internet filter for me. But I've had enough experts screw stuff up for me that I'm not trusting by nature. And Blaine doesn't have a shop down the street. So I'll do it and if I mess up at least I saved labor costs over paying someone else to screw it up for me.
I like the way the Jeep handles and performs now, so I'm picking the best route to end up back at this street performance and gain off road. But focus on off road first. Differentials first won't do that. It's probably why I see so many people regear more than once.
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that's a good point - since you've already run yours at that speed you know you're probably in the clear.
I'm dealing with a lot of variables - in one project I went from 4.56 in a TJ to 4.88 on an LJ with the same 32" tires. So I had new gears and a new frame/tub with a new wheelbase requiring a new driveshaft and a new pinion angle all at once. Would have been nice to separate the regear from the entire-rig swap so I could have known whether it was all driveshaft speed or something else. Nonetheless, running the numbers I know I wouldn't have the vibes I have if I was running 4.56 with 35s (which would be ok with my 6 speed) instead of 4.88 with 32s, and it's given me a sense of caution/hesitance about overgearing that I didn't have before.
Dave Kurth
New Member
I love to drive my 2002 TJ at the NC coast, where I live, with the door windows down and back window up, that's the bottom line. I have 3.73 gears with a 3 speed automatic with 4.0L and I don't think I will every see 20 MPG. I've been thinking about making changes. I'm not interested any major off road activities. I talked to transmission shop owner (a friend) about using 32HLE 4 speed transmission but he was not impressed with 4 speed since gets plenty of repairs/rebuilds and very seldom from 3 speed trans. I would appreciate any feedback. Dave
Leave the 3 speed, it’s a far better transmission. I do think you meant 42RLE instead of 32HLE but it doesn’t matter.
As for the 20 mpg, you’ll probably never see that but you wouldn’t with a 4 speed either. Most 4 speeds have such tall overdrives that they lug the engine. The best thing you can do for the 3 speed is regear appropriately and drive slower like 60-65 mph.
For the gears, most would agree that ideal ratios for tire sizes are:
30-32s - 3.73
33s - 4.10
35s - 4.56
37s - 4.88
Wait a minute. What transmission do you have? The 32rh or 42rle? What engine? What tire size? Gotta know those three things to know what gear ratio you should have
Increasing unsprung weight and bigger tires are the two reasons our Jeep mods kill gas mileage and range. I've done 33s 35s and the bigger the tire the worse the gas mileage regardless of ratios.
If you don't need floatation tires but you want better range and mileage, get shinnier, lighter tires. Changing from 33x190.50R15s to 7.50R16s, a 31" tall skinny tire git me 5mpg. From 17mpg to 22mpg, or a theoretical 95 mile range increase. And a way smoother ride too. Mine is a TJR so 6 speed OD and 4.10 ratios. My final drive is likely the same as you 3 speed automatic without OD thru 3.73 ratios.
Unsprung weight and rolling resistance are what kill gas mileage.
PS, that 3 speed automatic is one of the best transmissions made, don't change it.
If you don't need floatation tires but you want better range and mileage, get shinnier, lighter tires. Changing from 33x190.50R15s to 7.50R16s, a 31" tall skinny tire git me 5mpg. From 17mpg to 22mpg, or a theoretical 95 mile range increase. And a way smoother ride too. Mine is a TJR so 6 speed OD and 4.10 ratios. My final drive is likely the same as you 3 speed automatic without OD thru 3.73 ratios.
Unsprung weight and rolling resistance are what kill gas mileage.
PS, that 3 speed automatic is one of the best transmissions made, don't change it.
Okay so I have a 2001 Jeep TJ with a 4.0 and 307 Gears 3 speed automatic. I really don't care about mileage I tow it with my motorhome love to get where I'm going AND if punched at the light have lift power and be able to cruise at 60 65 with 33 inch tires no need to go faster not in a hurry but love the power and lift from the stoplight. Have the 30 and 35 Dana combo so do I need to upgrade the axles or will I be fine given that I'm not rough riding it Off Road but want to be able to crawl over obstacles not rock climbing just go four-wheeling have fun with the automatic so the wife can drive it.
I'm may tow up to 70 miles per hour so that is a factor
I am thinking 4:56 gears with an ox cable Locker in back and a SYE not sure about what to do in front...
I want excellent manners on the road when the wife driving but can be a mean little b**** when I want it to be
I have read every post on this thread....love the forum
I'm may tow up to 70 miles per hour so that is a factor
I am thinking 4:56 gears with an ox cable Locker in back and a SYE not sure about what to do in front...
I want excellent manners on the road when the wife driving but can be a mean little b**** when I want it to be
I have read every post on this thread....love the forum
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