Changed Axle Ratio = Better Gas Mileage?
Question:
I’m here in Canada driving a GMC 3500 Savana with a 454 engine and a gear ratio of 4.10 – I don’t ever pull anything behind this vehicle and 95% of the time it has six or fewer passengers and their luggage. I do a lot of highway driving and each month spend about $900-$1100 on fuel. It’s been suggested to me that I could change the axle ratio down to 3.53 and get 15% better gas mileage. I’ve been reading these two Chevy Truck news groups and seen varying opinion on whether changing the ratio would result in better economy or not. What all is involved in changing from 4.10 down to 3.53 ?? Is it even possible? I read the GM web page for this vehicle and it shows the only options for buying a new one as being 3.73 and 4.10 – Are there reasons to avoid going down even lower? Also, I’ve been told the change would cost me about $1000 but I’m wondering if this guy is missing out on some important details. One example would be (I’m told) that you’d also have to change the speedometer gear or else your speedo would report the wrong number and you’d get tickets. Can someone enlighten me on these matters? With the rise in gas prices I’m not opposed to the idea of using 15% less fuel. Thanks in advance Max
Response:
– Hide quoted text — Show quoted text – >I’m here in Canada driving a GMC 3500 Savana with a 454 >engine and a gear ratio of 4.10 – I don’t ever pull >anything behind this vehicle and 95% of the time it has >six or fewer passengers and their luggage. I do a lot of >highway driving and each month spend about $900-$1100 on >fuel. >It’s been suggested to me that I could change the axle >ratio down to 3.53 and get 15% better gas mileage. I’ve >been reading these two Chevy Truck news groups and seen >varying opinion on whether changing the ratio would result >in better economy or not. >What all is involved in changing from 4.10 down to 3.53 ?? >Is it even possible? I read the GM web page for this >vehicle and it shows the only options for buying a new one >as being 3.73 and 4.10 – Are there reasons to avoid going >down even lower? >Also, I’ve been told the change would cost me about $1000 >but I’m wondering if this guy is missing out on some >important details. One example would be (I’m told) that >you’d also have to change the speedometer gear or else >your speedo would report the wrong number and you’d get >tickets. >Can someone enlighten me on these matters? With the rise >in gas prices I’m not opposed to the idea of using 15% >less fuel. >Thanks in advance >Max
i’m not sure what’s involved in changing your gears, but i’d have to see some real numbers to believe 15% higher mpg/L…. i’ve heard of a few dodge rams that changed them and most got a few miles a gallon increase on the hiway… their in-town driving stayed the same or went down a bit, because you’re using a bit more gas to move the higher gears from a stand still…. mac http://www.aadtonline.com/Bios%20Files/mac%20davis.htm
Response:
Silver Surfer, I believe that you would get your best highway mileage with a 3.73 ratio. This is the most common ratio for passenger vehicles. Most of the GM vehicles came with this ratio. This includes cars/trucks equipped with 4 cyl. through small block V8’s. You have a very large engine that develops a lot of torque at low rpm’s. It will have no trouble getting you going from a stop light with a 3.73 ratio. Even a Chevy 350 could spin the tire from a stop with a 3.73. I would bet that you would get more than a 15% increase in MPG highway with a 3.73 , and you could still tow a very large boat, since you have a 1 ton truck, and large engine. Don’t knock your truck, it was built for serious business, but you don’t need the 4.10 gear for an everyday driver. The 4.10 gear would be good for towing a backhoe tractor on a trailer behind you. If you don’t have a backhoe, then you could change that gear to 3.73. You should look for a shop that specializes in rear ends. I am a master certified tech., worked for GMC 10 years, but I specialize in drivability and electronics. Having said that,… You would not go to a general practitioner for a hip replacement, would you? Although I could give you some advice on the subject, I’m not a rear end expert (except on women). 
I could count on my fingers, how many times I have set-up a new ring and pinion gear set in a vehicle. At that point, I heavily used the service manual for guidance. All of the repairs turned out fine though. Everyone was happy,… Thank God. As for your speedometer, there is no gear. There is a speed sensor mounted on the trans. You will need to go to a dealer to have the PCM (computer) re-programmed for the new axle ratio. Hope this helps you. If there are any other techs reading this post, any expert advise would be helpful to this person. GMdude
Response:
My question is this…Why are you driving a Big-Block 1Ton truck as a daily commuter??? Sell it to me, I defiantly could use it for what it was built for!!! You neglected to mention if it was 4wd or 2wd. The biggest problem you are gonna run into is the fact that your engine is broken in w/ the 4.10’s! Changing ratios will drop the revs below the level that the engine has always run at. 3.73’s would cause the fewest problems. You have a torque monster under the hood, they like gas, they also like lower revs! Your gear ratio will be limited to what ratios are available for the rear-end in the truck. 4.10 and 3.73 are available for almost all rears. A higher(numerically lower) ratio than that gets pretty hard to find for BIG rears like I am sure your truck has. Unless you have ALL the equipment you need AND the skill to do it, take it to someone w/ the training. Keep in mind that gas mileage gains are NOT the same from vehicle to vehicle. Someone w/ the exact same truck as you might get 5 points better MPG. you could lose point just as easily as you could gain them. It is a good idea to slow the spinning of that Rat down. Bigger typically needs slower! I repeated some things from other posts to your subject. Credit to them that I sampled!
Response:
3500 VAN usually is two-wheel drive
Response:
See http://www.gearvendors.com/
– Hide quoted text — Show quoted text -> I’m here in Canada driving a GMC 3500 Savana with a 454 > engine and a gear ratio of 4.10 – I don’t ever pull > anything behind this vehicle and 95% of the time it has > six or fewer passengers and their luggage. I do a lot of > highway driving and each month spend about $900-$1100 on > fuel. > It’s been suggested to me that I could change the axle > ratio down to 3.53 and get 15% better gas mileage. I’ve > been reading these two Chevy Truck news groups and seen > varying opinion on whether changing the ratio would result > in better economy or not. > What all is involved in changing from 4.10 down to 3.53 ?? > Is it even possible? I read the GM web page for this > vehicle and it shows the only options for buying a new one > as being 3.73 and 4.10 – Are there reasons to avoid going > down even lower? > Also, I’ve been told the change would cost me about $1000 > but I’m wondering if this guy is missing out on some > important details. One example would be (I’m told) that > you’d also have to change the speedometer gear or else > your speedo would report the wrong number and you’d get > tickets. > Can someone enlighten me on these matters? With the rise > in gas prices I’m not opposed to the idea of using 15% > less fuel. > Thanks in advance > Max
Response:
That’s about the craziest thing I’ve ever heard! According to your theory, every car in my state should have suffered a colapse in the late 80’s. That’s when the speed limit jumped from 55 to 70. All the sudden, every car was running a different rpm than it had been broken in with… CJB
– Hide quoted text — Show quoted text -> My question is this…Why are you driving a Big-Block 1Ton truck as a > daily commuter??? Sell it to me, I defiantly could use it for what it was > built for!!! > You neglected to mention if it was 4wd or 2wd. > The biggest problem you are gonna run into is the fact that your engine > is broken in w/ the 4.10’s! Changing ratios will drop the revs below the > level that the engine has always run at. 3.73’s would cause the fewest > problems. You have a torque monster under the hood, they like gas, they also > like lower revs! Your gear ratio will be limited to what ratios are > available for the rear-end in the truck. 4.10 and 3.73 are available for > almost all rears. A higher(numerically lower) ratio than that gets pretty > hard to find for BIG rears like I am sure your truck has. Unless you have > ALL the equipment you need AND the skill to do it, take it to someone w/ the > training. > Keep in mind that gas mileage gains are NOT the same from vehicle to > vehicle. Someone w/ the exact same truck as you might get 5 points better > MPG. you could lose point just as easily as you could gain them. It is a > good idea to slow the spinning of that Rat down. Bigger typically needs > slower! > I repeated some things from other posts to your subject. Credit to them > that I sampled!
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Response:
ROTFLMAO !
– Hide quoted text — Show quoted text -> That’s about the craziest thing I’ve ever heard! According to your theory, > every car in my state should have suffered a colapse in the late 80’s. > That’s when the speed limit jumped from 55 to 70. All the sudden, every car > was running a different rpm than it had been broken in with… > CJB > My question is this…Why are you driving a Big-Block 1Ton truck as a > daily commuter??? Sell it to me, I defiantly could use it for what it was > built for!!! > You neglected to mention if it was 4wd or 2wd. > The biggest problem you are gonna run into is the fact that your engine > is broken in w/ the 4.10’s! Changing ratios will drop the revs below the > level that the engine has always run at. 3.73’s would cause the fewest > problems. You have a torque monster under the hood, they like gas, they > also > like lower revs! Your gear ratio will be limited to what ratios are > available for the rear-end in the truck. 4.10 and 3.73 are available for > almost all rears. A higher(numerically lower) ratio than that gets pretty > hard to find for BIG rears like I am sure your truck has. Unless you have > ALL the equipment you need AND the skill to do it, take it to someone w/ > the > training. > Keep in mind that gas mileage gains are NOT the same from vehicle to > vehicle. Someone w/ the exact same truck as you might get 5 points better > MPG. you could lose point just as easily as you could gain them. It is a > good idea to slow the spinning of that Rat down. Bigger typically needs > slower! > I repeated some things from other posts to your subject. Credit to them > that I sampled! > —–= Posted via Newsfeeds.Com, Uncensored Usenet News =—– > http://www.newsfeeds.com – The #1 Newsgroup Service in the World! > —–== Over 80,000 Newsgroups – 16 Different Servers! =—–
Response:
With that much motor, the lower the revs the better. My truck gets its best mileage when going 60-65 mph, at 1800 rpm. Or an add-on overdrive like the other guy said (I think they’re spendy, but not sure).
– Hide quoted text — Show quoted text -> I’m here in Canada driving a GMC 3500 Savana with a 454 > engine and a gear ratio of 4.10 – I don’t ever pull > anything behind this vehicle and 95% of the time it has > six or fewer passengers and their luggage. I do a lot of > highway driving and each month spend about $900-$1100 on > fuel. > It’s been suggested to me that I could change the axle > ratio down to 3.53 and get 15% better gas mileage. I’ve > been reading these two Chevy Truck news groups and seen > varying opinion on whether changing the ratio would result > in better economy or not. > What all is involved in changing from 4.10 down to 3.53 ?? > Is it even possible? I read the GM web page for this > vehicle and it shows the only options for buying a new one > as being 3.73 and 4.10 – Are there reasons to avoid going > down even lower? > Also, I’ve been told the change would cost me about $1000 > but I’m wondering if this guy is missing out on some > important details. One example would be (I’m told) that > you’d also have to change the speedometer gear or else > your speedo would report the wrong number and you’d get > tickets. > Can someone enlighten me on these matters? With the rise > in gas prices I’m not opposed to the idea of using 15% > less fuel. > Thanks in advance > Max
Response:
My father in law had a big GMC step van similar to your truck in engine and power train. He hauled around a lot of tools and stuff in it and towed a big trailer sometimes but a lot of the time he was empty. He bought a motor home that had been wrecked at salvage that had an add-on overdrive and put the unit on his van. the only time he ever needed to shift down the over drive was when he was towing the trailer up in North Georgia mountains.
– Hide quoted text — Show quoted text -> See http://www.gearvendors.com/ > I’m here in Canada driving a GMC 3500 Savana with a 454 > engine and a gear ratio of 4.10 – I don’t ever pull > anything behind this vehicle and 95% of the time it has > six or fewer passengers and their luggage. I do a lot of > highway driving and each month spend about $900-$1100 on > fuel. > It’s been suggested to me that I could change the axle > ratio down to 3.53 and get 15% better gas mileage. I’ve > been reading these two Chevy Truck news groups and seen > varying opinion on whether changing the ratio would result > in better economy or not. > What all is involved in changing from 4.10 down to 3.53 ?? > Is it even possible? I read the GM web page for this > vehicle and it shows the only options for buying a new one > as being 3.73 and 4.10 – Are there reasons to avoid going > down even lower? > Also, I’ve been told the change would cost me about $1000 > but I’m wondering if this guy is missing out on some > important details. One example would be (I’m told) that > you’d also have to change the speedometer gear or else > your speedo would report the wrong number and you’d get > tickets. > Can someone enlighten me on these matters? With the rise > in gas prices I’m not opposed to the idea of using 15% > less fuel. > Thanks in advance > Max
Response:
Might be cheaper to run with smaller tires and make the the axle turn less. Poor mans fuel saver!
Response:
smaller tires = less circumference = more revolutions to travel a given distance = the exact opposite of what you just said. – Hide quoted text — Show quoted text – > Might be cheaper to run with smaller tires and make the the > axle turn less. > Poor mans fuel saver!
Response:
>smaller tires = less circumference = more revolutions to travel a given >distance = the exact opposite of what you just said. > Might be cheaper to run with smaller tires and make the the > axle turn less. > Poor mans fuel saver!
tall skinny tires?? (taller tire means lower revs, wider tire, more friction & drag) mac http://www.aadtonline.com/Bios%20Files/mac%20davis.htm
