ive got a few question about regearing. I own a 99 Chevy suburban (OBS). The rearend is a stock 10 bolt and came stock with GU6 (3.42s) and the G80.. I currently running 33x12.50s and she struggles on the highway and during towing. Every thing ive seen says i need to go to a 3.73. my question is will it help at all with towing and the highway struggle? Also how much if any does it affet my speedo reading? The 33s throw it off approx 3-5 mph at highway speed. Also is th 3.73 best or should i go lower? Any suggestions and advice would gladly be appreciated.
GEARS..??
- Thread starter thatboykg
- Start date
drewactual
Adventurer
it ought not mess with your speedo rating- that is a tone ring thing, or it's a speed sensor in the transmission... the tires affect your overall gear ratio, and they will affect your speedo reading..
you will be better served with 4.10:1 gears, and since you're considering changing, I'd go too low (numerically higher) than too high (numerically lower)...
here's why:
unless you run an overall gear ratio that provides WAY too much leverage for your purpose, such as 5.12:1 or 4.88:1, you're putting load on your engine and wasting energy. Your engine operates in a range of power dictated by power band, which is based off of the camshaft selection in relation to the available air, the lift and duration, and the displacement of the cylinders.. the stroke of the cylinders is of value, too... the displacement determines the proper amount of fuel (catalyst) to be squirted to fire the burn in perfect stioch ratio's of 14.7:1- your sensors monitor that- your foot opens the air and the engine responds accordingly.. when an engine is happily within it's engineered range of power it can easily maintain a 'crossing zero' lambda bounce of less than 3% either way... that is good.. when it is struggling to maintain (or build) power, it is running rich and not producing the power it's capable of... so... what do you do?
you alter the leverage... gears are the leverage... gears in your transmission, and gears in your axles... then, the leverage the diameter of tire figures into the ratio, as said before.
these things are built to meet 'most' expectations customers will put them through... they aren't built to specific purpose, which is up to us... and mod's to support a specific purpose are what we are all about- not just throwing performance parts at it for the sake of bolt on power you can do nothing spectacular with other than having... making the entire rig run in concert and benefit of each other is the ticket..
you're on the right path... gears, providing the leverage in the proper amount, is the easiest way to properly apply the engines energy to the ground..
if you bump to 3.73:1, you'll see an increase in performance and in economy- as measured with a vacuum gauge and demonstration that the engine isn't working as hard to produce the requested task.... if you slap a monitor on it, you'll watch the fuel trim approach zero, after planing off, and start crossing it... STFT's will adjust, making LTFT's adjust, and alterations to your environmental tables will occur, allowing the PCM/ECU to advance spark on a more stable engine, increasing power and economy...
if you bump to 4.10:1, you'll see even more increase...
if you bump to 4.56:1, with those 33's, you'll see a dramatic increase in available power (via leverage), faster accelerations (via leverage) and a dramatic drop in economy (because of wasted energy)... your transmission will appreciate it, though..
three items, and this is mathematics not magic: speed, RPM, overall gear ratio... give me two and I can tell you the third and be dead right every time... the only caveat to this is an unhealthy drive line such as a slipping transmission...
don't fear RPM's... your engine ain't worried about it (up to a point), and your gas usage is more based on engine load (expressed by that vacuum gauge or by monitoring a post exhaust port o2 sensor) more than RPM's... the gov't uses gear ratio's and engine displacement to determine fuel economy in most cases, using the formula i provided, but they do nothing about engine load... it's ALL about engine load.. finding the BALANCE of power produced and leverage to the terra is the game- and you're on it... I just rec the 4.10:1's over anything under it.
you will be better served with 4.10:1 gears, and since you're considering changing, I'd go too low (numerically higher) than too high (numerically lower)...
here's why:
unless you run an overall gear ratio that provides WAY too much leverage for your purpose, such as 5.12:1 or 4.88:1, you're putting load on your engine and wasting energy. Your engine operates in a range of power dictated by power band, which is based off of the camshaft selection in relation to the available air, the lift and duration, and the displacement of the cylinders.. the stroke of the cylinders is of value, too... the displacement determines the proper amount of fuel (catalyst) to be squirted to fire the burn in perfect stioch ratio's of 14.7:1- your sensors monitor that- your foot opens the air and the engine responds accordingly.. when an engine is happily within it's engineered range of power it can easily maintain a 'crossing zero' lambda bounce of less than 3% either way... that is good.. when it is struggling to maintain (or build) power, it is running rich and not producing the power it's capable of... so... what do you do?
you alter the leverage... gears are the leverage... gears in your transmission, and gears in your axles... then, the leverage the diameter of tire figures into the ratio, as said before.
these things are built to meet 'most' expectations customers will put them through... they aren't built to specific purpose, which is up to us... and mod's to support a specific purpose are what we are all about- not just throwing performance parts at it for the sake of bolt on power you can do nothing spectacular with other than having... making the entire rig run in concert and benefit of each other is the ticket..
you're on the right path... gears, providing the leverage in the proper amount, is the easiest way to properly apply the engines energy to the ground..
if you bump to 3.73:1, you'll see an increase in performance and in economy- as measured with a vacuum gauge and demonstration that the engine isn't working as hard to produce the requested task.... if you slap a monitor on it, you'll watch the fuel trim approach zero, after planing off, and start crossing it... STFT's will adjust, making LTFT's adjust, and alterations to your environmental tables will occur, allowing the PCM/ECU to advance spark on a more stable engine, increasing power and economy...
if you bump to 4.10:1, you'll see even more increase...
if you bump to 4.56:1, with those 33's, you'll see a dramatic increase in available power (via leverage), faster accelerations (via leverage) and a dramatic drop in economy (because of wasted energy)... your transmission will appreciate it, though..
three items, and this is mathematics not magic: speed, RPM, overall gear ratio... give me two and I can tell you the third and be dead right every time... the only caveat to this is an unhealthy drive line such as a slipping transmission...
don't fear RPM's... your engine ain't worried about it (up to a point), and your gas usage is more based on engine load (expressed by that vacuum gauge or by monitoring a post exhaust port o2 sensor) more than RPM's... the gov't uses gear ratio's and engine displacement to determine fuel economy in most cases, using the formula i provided, but they do nothing about engine load... it's ALL about engine load.. finding the BALANCE of power produced and leverage to the terra is the game- and you're on it... I just rec the 4.10:1's over anything under it.
Stumpalump
Expedition Leader
Do not put a penny into that weak 10 bolt. First call would be to junkyards. Tell them you want a stronger bolt in rear that has factory 4:10 and limited slip. Let their software sort out what drops right in. Last rear end I bought was less than the cost to regear what I had. Use an app like Waze or your GPS to tell you your correct speed.
jeep-N-montero
Expedition Leader
Both 3.73 and 4.10 axles are plentiful in junkyards, just remember you need to pull front and rear together so they MATCH.
ok well another thing to consider is right now i used this truck everyday and it sees alot of highway use. im gonna keep the 10 bolt in for now, is why i thought just regearing. Maybe later on i will get bigger axles when i do a SAS, and even then i will probably just buy some built G2s or something. But that probably wont be for several years, on account of having kids. lol. just wanted to find a quick fix to help out for now. This whole rig is kind of a budget build, i have less than $6500 in it right now, including cost of truck.
@drewactual- i understand what your trying to say, my trans does the slip (downshift) on every hill an alot if i have a head wind. this is one prob i was trying to cure as well. i was worried 4.10 would be way too much for it.
@drewactual- i understand what your trying to say, my trans does the slip (downshift) on every hill an alot if i have a head wind. this is one prob i was trying to cure as well. i was worried 4.10 would be way too much for it.
Depends on what you mean by "during towing" do you mean at speed or getting the load going from a stop? Lower gears will not help you go faster on the highway, pulling a pass, or any other time in which you are not in first gear. Gear changes change your overall ratios at each end, that is your lowest gear and your highest gear. So getting going from a light, that's your lowest gear and yes a lower ratio will help there. But as soon as your in second gear or higher it's moot. From there up until you are going fast enough to run out of RPM it's about the engine and transmission.
4x4junkie
Explorer
^^
That's not quite correct...
Deeper (numerically higher) axle gears indeed helps to find the appropriate transmission gear to best match the engine RPM to whatever situation is at hand (towing up a grade for example). It has the same effect as putting the transmission gear ratios closer together.
4.10 gears would definitely work well w/33s, though depending how deep your overdrive gear is, 4.56 might be even better still.
×2, forget about the 10-bolt, find a semifloat 14-bolt for it, Unless I'm mistaken, they bolt right up and can be had w/4.10s right from the wreckers, for much cheaper than regearing your 10-bolt too.
That's not quite correct...
Deeper (numerically higher) axle gears indeed helps to find the appropriate transmission gear to best match the engine RPM to whatever situation is at hand (towing up a grade for example). It has the same effect as putting the transmission gear ratios closer together.
4.10 gears would definitely work well w/33s, though depending how deep your overdrive gear is, 4.56 might be even better still.
×2, forget about the 10-bolt, find a semifloat 14-bolt for it, Unless I'm mistaken, they bolt right up and can be had w/4.10s right from the wreckers, for much cheaper than regearing your 10-bolt too.
It really depends and we don't have enough information. We just don't know enough, how fast he's trying to go, RPMS, how heavy he's towing etc. If his complaint is that he can't do 80 with a big wind drag 35' RV behind him then gears won't do him any good. The money he'd put into re-gearing both ends would be MUCH better spent on drivetrain.
Embrace the gear change - It is one of the basic modifications that I dragged my feet on completing on my Jeep, and I regret not doing in sooner. Over the years I slowly keep up-sizing the tires to a modest 31" tire. Performance suffered, poor mileage, and general drive-ability was horrible. Re geared it, and it was like a brand new vehicle. Yes, its an investment - but well worth it. Drove way better off road, drove better on the highway - just put everything back into the power band.
jeep-N-montero
Expedition Leader
I see them all the time in yards, not to mention that is what came stock in my truck.
Happykamper
Explorer
4:10 s are correct for your rear end. Get a AEV procal to set your speedo .
Yes it will help in all ways you require.
Drew actual is spot on.
Yes it will help in all ways you require.
Drew actual is spot on.
Those are the exact probs im experiencing. She just struggles, and trans cant seem to find right gear to keep up.
Ok guys.. good info. The main thing i tow is my rzr out to all the races. Its on a small 7x12 tandom axle trailer. My truck struggles to get up to 70, then the trans keeps downshifting and doesnt seem to find where its comfy. If its a short drive, i usually drop down a gear an run 55-60.. normal driving in town isnt too bad, Highway driving, terrible mileage and no balls, feels like im always dragging an anchor or something. The gears im looking at are only around $200 a set.. i just need to keep it reliable and dependable and get decent mileage for the time being. Like i said, i am planning to go big later on. Need it as a daily for now.
Yes the gears are cheap, but a whole working axle that bolts right in is the same price as the gears and in reality, easier to install.
Like said, find a 4.10 14 bolt at a junkyard and be done in a weekend.
Either way, regearing it will save your transmissions life. I ran my old truck almost always with overdrive shut off, unless I was doing 80 for an extended period of time because I had larger tires and didn't regear it.
Also, your speedo will likely be right where it should be after the gear swap. No need for a programmer.
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Like said, find a 4.10 14 bolt at a junkyard and be done in a weekend.
Either way, regearing it will save your transmissions life. I ran my old truck almost always with overdrive shut off, unless I was doing 80 for an extended period of time because I had larger tires and didn't regear it.
Also, your speedo will likely be right where it should be after the gear swap. No need for a programmer.
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Yup, I know concur, gears. 3.73 vs. 4.10 is a personal choice depending on driving habits and future plans. I'd lean 4.10 though.
.
I'm no longer a Chevy expert, had a couple suburbans but forgot a lot to make room for Ford knowledge, even then they were 2500s. I am however a big 14 bolt fan, it's a great axle, I just can't remember if the semi float version has the right 1/2ton lug pattern, I seem to think they are all 8 lug. Even if so, a 12 bolt, or just another 10 is very likely a much better and easier/cheaper task then changing gears.