Should I be Looking at Re-Gearing to 5:13's?

RamRod · Apr 29, 2014

Hi Guys,

I don't plan on doing this right way, but since I am keeping the 37's (maybe going + an inch or two in the future) should I be keeping a re-gear in mind.

I feel as if the OEM 4:10 gear ratio is just not right for me anymore given the modifications on my rig (mainly the Supercharger and 37's).

First gear in 4Lo is already crazy in this thing and I really only use it on descents to take advantage of the compression braking effect.

I need to learn more about this and thought this would be a great place to start!

I know 4speedfunk & Bebe has made this change, anyone else?

Thanks!

06 H3 · Apr 29, 2014

You can't regear lower then 4.56 with an oem front axle

SuperBuickGuy · Apr 29, 2014

I'd actually go the other direction - put 3.73s or similar gears.... you have the hp to turn the larger tires.

with that said... here's what to consider when gearing

1) use - rock crawling on the Rubicon is not the same as mud bogging in Oregon.
2) hp/torque range. In my C3 Corvette, I have 3.08 gears because anything higher (numerically) just makes a big smoke show before I lose the race.
3) mpg - GM sought the best mpg for their "normal" customer. For you, 4.10s work great without the blower and net you 14+ mpg. I live in Seattle, if you're not going up, you're going down... all while stuck in traffic. Top speed of my morning commute is less than 40 mph on my 10 mile commute... mpg sucks for me, so I'd be better off with 4.56s... except
4) intended use. I do SAR, which normally means either towing some poor sap out of the mountain or transporting people up closed roads to as close to the subject as possible. I wouldn't need low range if I had 4.56 gears (and with 4.56 gears, you're increasing leverage, thus stressing axles and CVs). In my case, going to 37s (keeping my 4.10s) would be of benefit(ish) because I'd get the use of my low range again... after all, that's the point of multiple speed transfer cases - maximizing power... (I am going to 35s, I think 37s are too much of a strain).

and lastly,
don't overpower your axles. unless you're having trouble pulling something, your gears are either good or a bit too high numerically. I've been eyeing a 6.2 L VVT motor, except I'm more concerned about adding 400 hp to an already small front differential..... I was amazed at how small that 760 AAM differential is - too much power and that little thing is going to go boom.... even if you play nice.

to recap - decide what you're going to do; the gear appropriately for it so that on the highway you're 500 rpm less than your hp curve starts (normally, 1500 rpm); yet on the trail, you can center your rpms at 3500-4000 rpm (peak torque/hp range).

backcountryislife · Apr 29, 2014

if you re-gear to 4.56, I'd give serious thought to getting the CI front Diff... (or does the 09 alpha already have that?)

Either way, can't imagine going up, but if you already feel like 4lo is super low, why are you wanting to go lower?

Pappibri · Apr 29, 2014

:corn::huh:

RamRod · Apr 30, 2014

backcountryislife said:
if you re-gear to 4.56, I'd give serious thought to getting the CI front Diff... (or does the 09 alpha already have that?)

Either way, can't imagine going up, but if you already feel like 4lo is super low, why are you wanting to go lower?

My original thinking is that, I have only ever seen people lower their gearing when they went to 37's (in H3's) and figured they knew more then me haha!

RamRod · Apr 30, 2014

backcountryislife said:
if you re-gear to 4.56, I'd give serious thought to getting the CI front Diff... (or does the 09 alpha already have that?)

Either way, can't imagine going up, but if you already feel like 4lo is super low, why are you wanting to go lower?

Yes the 09 Alpha does come with the CI diff, so I do at least have that covered.

RamRod · Apr 30, 2014

SuperBuickGuy said:
I'd actually go the other direction - put 3.73s or similar gears.... you have the hp to turn the larger tires.

with that said... here's what to consider when gearing

1) use - rock crawling on the Rubicon is not the same as mud bogging in Oregon.
2) hp/torque range. In my C3 Corvette, I have 3.08 gears because anything higher (numerically) just makes a big smoke show before I lose the race.
3) mpg - GM sought the best mpg for their "normal" customer. For you, 4.10s work great without the blower and net you 14+ mpg. I live in Seattle, if you're not going up, you're going down... all while stuck in traffic. Top speed of my morning commute is less than 40 mph on my 10 mile commute... mpg sucks for me, so I'd be better off with 4.56s... except
4) intended use. I do SAR, which normally means either towing some poor sap out of the mountain or transporting people up closed roads to as close to the subject as possible. I wouldn't need low range if I had 4.56 gears (and with 4.56 gears, you're increasing leverage, thus stressing axles and CVs). In my case, going to 37s (keeping my 4.10s) would be of benefit(ish) because I'd get the use of my low range again... after all, that's the point of multiple speed transfer cases - maximizing power... (I am going to 35s, I think 37s are too much of a strain).

and lastly,
don't overpower your axles. unless you're having trouble pulling something, your gears are either good or a bit too high numerically. I've been eyeing a 6.2 L VVT motor, except I'm more concerned about adding 400 hp to an already small front differential..... I was amazed at how small that 760 AAM differential is - too much power and that little thing is going to go boom.... even if you play nice.

to recap - decide what you're going to do; the gear appropriately for it so that on the highway you're 500 rpm less than your hp curve starts (normally, 1500 rpm); yet on the trail, you can center your rpms at 3500-4000 rpm (peak torque/hp range).

Typical use, first and foremost its a daily driver, I put on about 15,500 miles last year and most of it was highway.

As for the off road use, 6-8 months a year is snow wheeling, then the rest of the year is dirt trails, mud (with high sand content), scattered rocks (nothing like Moab), a week in moab every two years or so...

4speedfunk · Apr 30, 2014

5.13s?....oh hell yes! They make a drastic improvement in drive-ability (with the 5-cyl). They essentially put the motor back into the rpm range it was intended to operate in. I cruise at 65mph at 2000 rpms with 37"s, and the truck does not downshift or hunt between gears like it used to. I will also note that if you stab the throttle from a dead stop...you had better have the thing pointed in the direction you want to go! Shifts come hard and fast, and full-throttle 0-40mph runs can be quite exciting. The biggest challenge is keeping the motor out of the redline, as it revs so quickly...its sometimes hard to control shift points. I don't accelerate like this very often just because it tends to get a tad busy for the driver and I'm sure...quite stressful on the drivetrain. As far as "normal" driving...the 5.13/37"s combo works great. I also have an ECM tune, TCM-tune, and speedo correction from PCMofNC.

The improvement you're seeking is most predominant in high-range. I think most everyone will agree that a 4:1 t-case is awesome...regardless of axle gearing, and the problem with big tires is IMO...limited to daily street driving (rather than off-roading). Simply put...an H3 with the Adv. Pak does not need lower axle gearing for low range...it needs it for high-range! Of course, there are huge benefits in low-range as well...but that's not really why I chose lower gearing. Low-range with 5.13s is downright insane...and I will be the first say its sometimes hard to fend-off a boner when crawling in low-range. I'm talking John Deer tractor low! So low that anything less than 37"s is almost pointless.

Knowing what I do now, after a year and a half with this set-up...my next H3 will have a lower stance, 4.88s, and 35" tires. I realize this might seem like a step backwards but, it has more to do with engineering the perfect all-around rig...and less to do with making a monster off-roader. 37"s and 5.13s are at the limit (possibly a bit past) for a sensible daily driver rig. I would even go back to 33"s and 4.56s if the SAS didn't require so much lift. A bone-stockish H3 with a SAS would be killer. I just can't find a way to do it without at least 6" of lift, and larger tires are needed to sort of fill-in the wheel-wells and complete the package.

Alpha guys can probably get away with less gearing. The broad torque range of the V8 isn't as effected by larger tires.

SuperBuickGuy · Apr 30, 2014

4speedfunk said:
5.13s?....oh hell yes! They make a drastic improvement in drive-ability (with the 5-cyl). They essentially put the motor back into the rpm range it was intended to operate in. I cruise at 65mph at 2000 rpms with 37"s, and the truck does not downshift or hunt between gears like it used to. I will also note that if you stab the throttle from a dead stop...you had better have the thing pointed in the direction you want to go! Shifts come hard and fast, and full-throttle 0-40mph runs can be quite exciting. The biggest challenge is keeping the motor out of the redline, as it revs so quickly...its sometimes hard to control shift points. I don't accelerate like this very often just because it tends to get a tad busy for the driver and I'm sure...quite stressful on the drivetrain. As far as "normal" driving...the 5.13/37"s combo works great. I also have an ECM tune, TCM-tune, and speedo correction from PCMofNC.

The improvement you're seeking is most predominant in high-range. I think most everyone will agree that a 4:1 t-case is awesome...regardless of axle gearing, and the problem with big tires is IMO...limited to daily street driving (rather than off-roading). Simply put...an H3 with the Adv. Pak does not need lower axle gearing for low range...it needs it for high-range! Of course, there are huge benefits in low-range as well...but that's not really why I chose lower gearing. Low-range with 5.13s is downright insane...and I will be the first say its sometimes hard to fend-off a boner when crawling in low-range. I'm talking John Deer tractor low! So low that anything less than 37"s is almost pointless.

Knowing what I do now, after a year and a half with this set-up...my next H3 will have a lower stance, 4.88s, and 35" tires. I realize this might seem like a step backwards but, it has more to do with engineering the perfect all-around rig...and less to do with making a monster off-roader. 37"s and 5.13s are at the limit (possibly a bit past) for a sensible daily driver rig. I would even go back to 33"s and 4.56s if the SAS didn't require so much lift. A bone-stockish H3 with a SAS would be killer. I just can't find a way to do it without at least 6" of lift, and larger tires are needed to sort of fill-in the wheel-wells and complete the package.

Alpha guys can probably get away with less gearing. The broad torque range of the V8 isn't as effected by larger tires.

and he has an alpha.

RamRod said:
Typical use, first and foremost its a daily driver, I put on about 15,500 miles last year and most of it was highway.

As for the off road use, 6-8 months a year is snow wheeling, then the rest of the year is dirt trails, mud (with high sand content), scattered rocks (nothing like Moab), a week in moab every two years or so...

then I'd suggest 3.73s. I know the 4x4 magazines get all in a tither about anything less than 4.56s for 36 or taller; but honestly, they're a legend in their own minds and that's pretty much it.

I have a diesel pickup (same weight as the hummer, ironically - 83 Chev 4x4 3/4 ton)... and I've run 36s on it with 4.10 gears - it works just fine and I use the truck as a truck, so far it's best tow was camper/corvette over snoqualmie pass (5k feet up from sea level) at the speed limit.... camper is 3500 lbs, truck is 5500 lbs, trailer is 2k and the corvette is 3300... call it 14,000 with people and food.... with 4.10s, on bias ply 36s at 65 mph grade tends to 5%.... according to the tv shows and the magazines, I shouldn't have been able to get out of my driveway (it does have a turbo, but that's only really useful at speed).... call it 250 hp, 350 torque - so equivalent numbers.... and I got 13 mpg while doing it.

backcountryislife · Apr 30, 2014

Honestly, if there's not a problem to be solved with gearing, and you feel that you're low enough off road... I wouldn't spend the money on a re-gear.

With the 5 cyl 3 or my 6 cyl JK... HELL YES, LOWER IS BETTER, but your ride isn't exactly lacking bottom end from the sound of it.

I'd spend some $$ on other mods... suspension, whatever... seems like where you're at is a good place.

ReconH3 · Apr 30, 2014

I ran 4.88 on 37"s and 5.13 on 40" now. Both kept my speedo spot on to match the original factory setup.

"Ex Umbris Venimus"

SuperBuickGuy · Apr 30, 2014

Part of my issue with gear changes - I had a 2006 GTO, and got convinced to go to 3.91 gears. All it did was make my 6 speed into a 5 speed because 1st gear became absolutely worthless. The point is, do the math, figure out what rpm you want to run and where then gear appropriately for that.... oh, and as an added bonus, lowering (numerically) gears doesn't mean better mpg - the point of gears is to put the motor in the place where it can do work most efficiently.

4speedfunk · Apr 30, 2014

A 5cyl. H3 with 3.73s will barely be drive-able. I would be surprised if it would even shift into 4th gear...even with stock 285 tires.

Panzer07 · Apr 30, 2014

So if in getting this correct....running a 5.13 TC with 37" tires on my I5 I should be good to go with no problems if I decide to ditch the 35 and go up to 37" or 40"...I'm not planning on doing this any time soon tho my 35 are still 95% thread and I'm working on getting the rancho lift kit...but I would like to keep this in my for when It comes time to upgrade my TC since I do t have the 4.1

Sent From Someone Else's iPhone 'Cause I'm Too Broke To Own One.

06 H3 · Apr 30, 2014

I agree. Its downright laughable at how gutless my I5 is. Granted I have the 3.5 compared to the 3.7 but going up a steep grade on the back side of big bear loaded down with gear, tools, food, 2 people and a dog with more stuff then what I brought on the trip I was barely holding 2nd gear on the steep grade and dont forgot the 50mph headwind to add to the steep grade. Granted, my 3.5 is more gutless then normal because I have a clogged cat a crack in the exhaust and a really really dirty throttle body from engine blow by but if I plan to resolve all those engine problems soon and get a PCM tune which doesnt help either but moral of the story is 5.13s would be in my truck if I could easily do it. I still plan to but now its just harder.

RamRod · Apr 30, 2014

Torres Fernando said:
So if in getting this correct....running a 5.13 TC with 37" tires on my I5 I should be good to go with no problems if I decide to ditch the 35 and go up to 37" or 40"...I'm not planning on doing this any time soon tho my 35 are still 95% thread and I'm working on getting the rancho lift kit...but I would like to keep this in my for when It comes time to upgrade my TC since I do t have the 4.1

Sent From Someone Else's iPhone 'Cause I'm Too Broke To Own One.

The 5:13 gearing is at the axles no the TC, but yes from the sounds of it the I5 could benefit from the re-gear if jumped up to 37's

So just to be clear I am talking about my Supercharged Alpha, that makes plenty of bottom end (reported around 430hp at the crank), but does too much gear hunting on the highway while towing. That's the main reason i feel it needs a re-gear

Panzer07 · Apr 30, 2014

RamRod said:
The 5:13 gearing is at the axles no the TC, but yes from the sounds of it the I5 could benefit from the re-gear if jumped up to 37's

So just to be clear I am talking about my Supercharged Alpha, that makes plenty of bottom end (reported around 430hp at the crank), but does too much gear hunting on the highway while towing. That's the main reason i feel it needs a re-gear

Ok thanks for explaining that I was confuse between the TC and axles...so then 5:13 gears on the axles and a 4:1 transfer case should be good a good match or the TC has little to do/play here

Sent From Someone Else's iPhone 'Cause I'm Too Broke To Own One.

SuperBuickGuy · Apr 30, 2014

4speedfunk said:
A 5cyl. H3 with 3.73s will barely be drive-able. I would be surprised if it would even shift into 4th gear...even with stock 285 tires.

I had an 05 Colorado with exactly that set up.... I really had no complaints about its power. But I'm kind of weird, I don't believe in "one-rig-to-rule-them-all" I have 5 cars and trucks which each fulfill a specific purpose.

4speedfunk · Apr 30, 2014

Yeah...its not a true apples-to-apple comparison. I think the larger tires that come stock on the H3 pretty much require a 4-series gear. The only exception might be CaseyS's diesel H3.

True. It takes five cars to have a bad-ass ride in every category...no way around it. Are any of you guys old enough to remember "Speed-buggy"? It would be so cool to just push a button and have your car morph into some other specialized vehicle?...

[video=youtube;3hx-hEWl10c]https://www.youtube.com/watch?v=3hx-hEWl10c[/video]

amrg · Apr 30, 2014

Technically speaking, an H3 alpha running 37s need to run 4.88 gears to have better performance than a stock Alpha running 33s.
Ive run my Alpha with 32s (how they come factory here) and the truck is really fast, 4.88 gearing would also net me same performance if I ran 37s qheb compared to 32s on 4.10 gears.
If i was gona regear, Id go either 4.88 or 5.10 on an Alpha, but its not an available option.

SuperBuickGuy · Apr 30, 2014

4.88 gears in a Toyota 4 cyl sized front carrier with 300 hp will equal a lot of axles and blown differentials.

amrg · Apr 30, 2014

SuperBuickGuy said:
4.88 gears in a Toyota 4 cyl sized front carrier with 300 hp will equal a lot of axles and blown differentials.

Exactly. Plus it won't fit hence why no one has done it. If some how a bigger diff was to be put in an H3 (it workes oncw before) that would've been my target. 4.88s and 37s!

SuperBuickGuy · May 1, 2014

the weakest bit is the carrier itself, the 28 spline axles can handle a lot of hp and abuse, next weak link is the CV joint itself.... Just have to change the center section - which is why I'm looking at either a 9" or 44 center. Since you're not supporting huge tires (because it's not part of the suspension, as a solid axle is), the 44 should be more than enough up to 38s or even 40s. It can be done, and actually should be price-wise in line with rebuilding the AAM 760... hmmmm, do I have a 44 housing around here to play with.....

atvspeed4 · May 1, 2014

Look for the threads we have on here with IFS diffs. We have tried to fit several custom housings in at our shop and non have worked out. The 8.5/8.6 ten bolt was not even close to fitting as the pinion was too close to the motor.

Should I be Looking at Re-Gearing to 5:13's?

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