Torque to Gear to Tire Size

[Infidel Edition]

OK. I know there's a million threads on use #.## for tires in the ## - ## range and fuel economy and ....

My question is, with 3.07 gears & 30" tires...otherwise stock 5 speed manual
I get great mileage at 65
But when I'm driving over the pass, it's sluggish at best.

I am looking at getting lower gears. But I'm also getting ready to complete a 4.6 stroker.
So I'll be upping my torque by ??

Is there a Foot Lb to GVRW to gear formula?
I don't do crawling. And for most of the off road that I do, the gearing is fine.
I just want to have a little extra on the big hills.

If I up the torque by 15% or more ... how much difference in gearing would that equate to?
Like a 3.73 vs 4.10's

[Cheromaniac]

My question is, with 3.07 gears & 30" tires...otherwise stock 5 speed manual
I get great mileage at 65
But when I'm driving over the pass, it's sluggish at best.

I am looking at getting lower gears. But I'm also getting ready to complete a 4.6 stroker.
So I'll be upping my torque by ??

With a 15% increase in engine displacement, you can expect roughly a 15% increase in peak TQ.
I'm running a 4.6 stroker in my XJ. It's also a 5-speed with stock 3.07 gears but my tires are only 27.4". I feel that the gearing on my Jeep is just about ideal and it'll effortlessly pull up highway inclines in 5th gear.
Your tires are 10% bigger so you'll need proportionately higher ratio axle gears. The closest would be the 3.55s that came in the automatic XJs, so it might be cheaper to get the complete axles from a junkyard rather than doing the ring & pinion swaps in your own axles.

[Infidel Edition]

With a 15% increase in engine displacement, you can expect roughly a 15% increase in peak TQ.
I'm running a 4.6 stroker in my XJ. It's also a 5-speed with stock 3.07 gears but my tires are only 27.4". I feel that the gearing on my Jeep is just about ideal and it'll effortlessly pull up highway inclines in 5th gear.
Your tires are 10% bigger so you'll need proportionately higher ratio axle gears. The closest would be the 3.55s that came in the automatic XJs, so it might be cheaper to get the complete axles from a junkyard rather than doing the ring & pinion swaps in your own axles.

Thanks. I was thinking about getting a newer 29 spline axle anyway. I picked up a drum to disk conversion kit ... and was thinking about swapping the axle shafts at the same time since I have to pull them out to do the swap.

I'll keep my eye out for a 3.55 or 3.73 set from a newer XJ instead.

:xj-red:

[MattybPDX]

26 West coming out of the tunnel I slow to a crawl, need to get all the way over so people stop passing me on the right.

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[Infidel Edition]

26 West coming out of the tunnel I slow to a crawl, need to get all the way over so people stop passing me on the right.

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what size tires do you have?
......I have zero problems on 26 with 30" tires and 3.07 gears

[MattybPDX]

27" with stock gears

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[MattybPDX]

I also go easy, haven't really tried punching it to see how she does.

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[Infidel Edition]

27" with stock gears

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4 banger?
... you shouldn't be having issues on that hill. Unless you have a lot of extra weight in the back.

[Infidel Edition]

I also go easy, haven't really tried punching it to see how she does.

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I'm usually 4th gear pushing a little to go 55. But I can speed up if needed.
.....not a fast acceleration, but speed up.

[bluedragon436]

So my question is... with running a 4.6l stroker... would 4.56 33's or 35's be horrible??

[Infidel Edition]

So my question is... with running a 4.6l stroker... would 4.56 33's or 35's be horrible??

That's kind of what I was wondering.
4.56 with 35s might be the sweet spot.
I've seen the gear to tire size chart, but it's based on stock output... right?

The sweet spot for the gear ratio should be based on torque @ RPMs during primary usage for the weight of the vehicle.
So, with 30"s, or 32"s, if it's a highway driver 3.5/3.73 would be better ... But a crawler would prefer 4.55.
For towing on hwy, maybe 4.10s

[Infidel Edition]

...I'm asking not recommending

[Cheromaniac]

Here's what I'd recommend as a rough guide for a 3500lb curb weight Jeep with a 4.6L stroker and a 5-speed manual tranny. Keep in mind that other factors also need to be considered.

27-28" tires: 3.07
29-31" tires: 3.55
32-33" tires: 3.73
34-35" tires: 4.10

Bigger wheels add extra weight, and extra weight on the vehicle itself needs to be compensated with shorter, numerically higher ratio, gearing (10% more weight requires 10% higher ratio gears than those quoted above). The extra aerodynamic drag at highway speeds induced by lift kits also needs to be compensated with shorter gearing.