I didn't read most of this article, just the first portion where he lists the types of axles for the tires, and it makes no sense to me based on real world. . Currently running 4.10, with 35's, 4.0l, slightly built, and basically stock rebuilt transmission, it runs much better than it did with 4.56. It was almost undriveable on the highway with 4.56 gears. Engine was screaming constantly. I had just come online here to get some info, but it seems there is some tremendous confusion on my part. Having problems with rear end, and thought I should learn some things, but??? I have almost too much low end at every speed now, with 4.10's, and everyone on here seems to think I should have way different ration in direction that was almost undriveable before.
Gear ratios and bad advice
- Thread starter Brantley
- Start date
absolutely, 100% I agree. Well said, prepare to get flamed.
With 35s and a clutch, I tend to like 4.10s, with 33s I swear by 3.73s. But I fully understand the screaming rpms.
3000rpm is the ideal, responsive rpm "cruising" thru the mountains and traffic but 2000rpm, 2200rpm is the ideal crusie on the highway. Guys who gear for power in overdrive have zero understanding of gearing. Race cars have NO overdrive because direct, down 1 gear in a Wrangler is the most efficent gear. Gear for power in direct, 4th in a 5speed. 5th in a 6speed, and use OD to drop the rpms, gain fuel efficiency, quiet the drive.
Even if you are building a race Wrangler, OD, 5th or 6th is the worst gear to win a race with. Way too many guys on these Foums with loud mouths and zero education.
In North America OD transmissions came about thanks to the oil embargo and gas shortages. Today the hottest cars achieve top speed, 150mph in 5th gear and use 6th, 7th, 8th gear to drop rpms, make the ride quieter, more efficient and extend the life of the powertrain. I'll get flamed. you will get flamed. But you are correct, The engine SCREAMS if you follow the advice on this forum.
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everyone seems to have missed this point
this forum centers on off roading, not highway driving
if you are building to climb a waterfall they might be correct
but if they actually listen to the writer, screaming constantly on the highway
they might get it. you are quite right Joe, so is the opinion of this forum, if you have a trailered rock crawler
unfortunately Chris has been unable to differentiate between the two,
Most Wranglers are daily, highway drivers
This forum caters to the minority who have zero tolerance of the majority
You and I have been doing this for 7-8 years. For at least that long the gear recommendations have always been for the highway. For at least that long, you have been ignoring that point.
And it doesn't matter how often we remind you of this point. You continue to ignore it.
well, I was literally one of the first on this forum. and far from ignoring, I keep making the point which you guys, keep ignoring. The point and the technology and the industry standard. OD is not the gear to focus on for power, the direct gear is. Shotgun to the head because you guys keep ignoring what has been an industry gearing design fact for 50 years in North America...... even longer if you look at Europe.
Like I said, we will all get flamed for disagreeing with the few on this forum who just don't get it.
Look at the avatar if you need to know where the post is coming from
However, I never argued with anyone here, just stated my opinion.
Obviously I have threatened the status quo who feel anyone with a different opinion must be dealt with.
Unfortunate because otherwise Chris runs a great forum. And TJs are my passion.
On my third now, Over 400K miles of experience.... mostly highway obviously.
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The problem with all of that drivel is what is considered "screaming". That and I could not give a shit less what it does off road. I gear for the street, period because if you can't drive to the trail regardless of how far away it is, then I did not do my job correctly.
The problem with all of that drivel is what the auto industry has done in general has nary a fucking thing to do with the TJ. It came from the factory in 97-02 with a 4.0 and a transmission that put the 68 mph cruising RPM at 3000 when the speed limits were well above the expired nationwide 55 mph max. What part of the auto industry thought that was a good idea?
He's actually right for my application. If I regeared as recommended here I'd be at 3200 rpm at interstate speeds if I drove slow and stayed at the speed limit.
My 32 inch tire, 3.73 gear combination has me at 2684 rpm at 80 mph in 6th gear with the NV3550 manual transmission. If I want higher rpms I can shift down to 5th and be at 3800 rpm.
That's the beauty of a manual. I set the rpm. Not the rear differential gearing. And it's the point being lost. If you drive an automatic regearing is your answer. If you drive a manual, shifting at the same rpm after tire changes is your answer.
Off road if you have 3.73 gears you can buy a 5:1 or 6:1 atlas transfer case to compensate. They cost the same as a 4.3:1. Then on road your jeep drives closer to stock.
But we're mixing advice. Just like the OP breaking down by engine and transmission, we need to add use categories. You can compensate for different on and off road performance issues with different equipment modifications. Axle ratio is only one of several in the powertrain.
With a manual transmission, I can compensate for 30" versus 35" tires by not shifting until I reach the same engine RPMs. Doing so holds the final gear ratio from engine to tire at roughly the same for a given engine RPM and the engine doesn't see too much of a difference. If I regear the rearend for 35" tires I'd likely shift the transmission earlier into a higher gear. Effectively wasting some of my regear.
Automatic transmissions do not give you that sort of flexibility unless you own some of the newer models that allow you to electronically hold the gear.
First gear takeoff with the manual 6 speed and larger tires might be a point I can't control, but 1st gear is already low so up to 35" tires shouldn't be noticeable. I might not have to shift before I get through intersections anymore. But regearing has similar affects on the high end side when you get to that limit.
When we lay out our gear recommendations by transmission, it's helpful to add the gear ratios of each transmission gear. It's why grim jeepers site is so helpful. I can look at my individual traffic patterns and find speed rpms for each gear point. I'd hate to select a rear differential gear that had me shifting up and down between 2nd and 3, or 3 and 4, while stuck in traffic during in my normal daily drive. Who needs that sort of constant clutching.
I'll let everyone look at the charts and base their recommendations off some generic internet information. But it's never been my style not to think it through completely and tailor any final solution to my specific needs.
If I leave my 3.73 gears in and put on 35" (likely 34") tires my engine RPM at interstate speeds would be 2450 RPM and I could stay down a gear and rev up to 2950 RPM if needed. Not significantly different than my current setup which works for me all around. Then when I go transfer case shopping I'll get a 5:1 ratio instead to compensate for my rear differential gearing. That would come close to doubling my current crawl ratios.
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so to throw another thought in picking gears
My question is most charts show tire size equal gear ratio of X.XX. Does that apply to actual tire size or manufacture stated because what I have seen most 31’s Are actually closer to 30 and that pattern seems to follow with tires actually smaller then stated
My question is most charts show tire size equal gear ratio of X.XX. Does that apply to actual tire size or manufacture stated because what I have seen most 31’s Are actually closer to 30 and that pattern seems to follow with tires actually smaller then stated
This has been beat to death. If you don't know the actual rolling radius of the tire you are running, then you wind up with garbage in and garbage out on the calculators.
Well, sort of. You still have the same five gears to choose from. For those of us with stock 3.07 gears that weren't great to begin with, and now have larger tires, it sucks. Even first gear is too weak.
Gearing up your differential(s) is a simple trade off. You gain torque in every gear at the expense of top speed. And of course cruising along in your top gear at any given speed will have higher rpms than before.
InOmaha said:
The NV3550 is a five speed, fifth gear is a .78 ratio. If yours is the six speed that's the NSG370, with a .83 ratio sixth gear. You would also have a taller first gear than the NV3550, making it easier to launch. Overall you're in a better spot with the NSG370 vs the NV3550.
With the six speed at 65mph, 32 inch tires, 3.73 gears, in sixth gear you'll be at 2100rpm. A bit low IMO. Sure you can shift down, but that impacts fuel economy. For cruising at highway speeds I want to stay in my top gear for anything short of a steep grade. The 4.0 is just starting to make decent power at 2200rpm. As for fuel economy at higher speeds aerodynamics are the #1 problem there. Engine rpm changes due to regearing won't have much effect. Having to downshift frequently will though.
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