Noticeable difference in axle ratio?

dr9672723 · July 7, 2004

If anyone has experience with this question, I would appreciate your opinion, please.

2003 Silverado, 4.3 V6, 3.42 axle, P25570R16 tires.

I love my gas mileage but occasionally tow a 2500 lb. trailer. I'm wondering how much difference, if any, it would make to switch to a 3.73 to help a little bit more with the trailer, without making a dent in my MPG?

Thanks,

Dan

99-2door · July 7, 2004

You might actually find that your mileage may increase with the lower gear ratio. Seems counter-intuitive, but since the truck may not down shift so much you may get better mileage. Gearing is a tricky thing to get right and it depends on the driver, engine, transmission, terrain and grades.

snoman · July 7, 2004

If anyone has experience with this question, I would appreciate your opinion, please.

2003 Silverado, 4.3 V6, 3.42 axle, P25570R16 tires.

I love my gas mileage but occasionally tow a 2500 lb. trailer. I'm wondering how much difference, if any, it would make to switch to a 3.73 to help a little bit more with the trailer, without making a dent in my MPG?

Thanks,

Dan

I would not waste time with a switch to 3.73, I would go to a 4.10 to really see a difference with a 4.3. Your MPG will not decrease as some would lead you to believe as engine would run closer to its sweet spot cruising where it uses less fuel per HP hour and OD will be a lot more usable to and I would look for MPG while towing to increase too. If you never towed at all 3.73 would be a good base gear with that engine and stock tires.

dr9672723 · July 7, 2004

Thanks. I appreciate your opinions.

Mort · July 7, 2004

Don't forget to factor in getting your PCM corrected for the new gears by the dealer or an aftermarket PCM or handheld tuner. Anything in the PCM that uses vehicle speed as a factor will be thrown off if you don't such as shift points.

The 3.73 represent about a 9% change in gearing and your speed will be off by this amount. So you will be going about 54.6 mph when your speedo reads 60 mph.

The 4.10 represent about a 20% change and you will be going about 48 mph when your speedo reads 60 mph.

Not really sure how the gears will affect your mileage and it might in fact improve in certain circumstances because the engine will not have to work as hard to accelerate or to hold a given speed.

The driveability of your truck will be greatly improved and I am sure it will feel like a new truck. If you tow much or want to wake your truck up a little then maybe a small hit in gas mileage won't hurt so bad.

The 4.10 gears will really make a difference that you can notice.

snoman · July 7, 2004

Don't forget to factor in getting your PCM corrected for the new gears by the dealer or an aftermarket PCM or handheld tuner. Anything in the PCM that uses vehicle speed as a factor will be thrown off if you don't such as shift points.
The 3.73 represent about a 9% change in gearing and your speed will be off by this amount. So you will be going about 54.6 mph when your speedo reads 60 mph.

The 4.10 represent about a 20% change and you will be going about 48 mph when your speedo reads 60 mph.

Not really sure how the gears will affect your mileage and it might in fact improve in certain circumstances because the engine will not have to work as hard to accelerate or to hold a given speed.

The driveability of your truck will be greatly improved and I am sure it will feel like a new truck. If you tow much or want to wake your truck up a little then maybe a small hit in gas mileage won't hurt so bad.

The 4.10 gears will really make a difference that you can notice.

Good point on a ECM reprograming. You could gt dealer to do it for a feee or a after market unit such as a Hypertech allows you to eaisilt adjust for axle ratio and tires size yourself and you can get them pretty cheap on Ebay too.