You need to keep in mind that the only thing changing ratios does for you is give you better acceleration off the line. People seem to think that it gives you "more power." It doesn't. The power available from the engine is the same, and it will take X power to move Y trailer in Z conditions no matter the gear ratio.
If you're able to haul the trailer in 3rd, save your money and haul it in 3rd. 3rd is 1:1, which always was top gear until they started putting overdrives in pickup trucks.
My older 5.4 with 4.10 will stay in OD if the road is perfectly flat and no headwind. When I had 3.55 I could barely hold 3rd. You will not really gain much swapping to 4.10 just to use OD but you will love the drivability after the change both towing and not towing. I mostly use 3rd even after changing to 4.10 and it runs at 2500 rpm down the road at the 55mph CA speed limit. If you are running faster, then OD is more possible as the RPM will be up. Changing gears is a measured improvement not a silver bullet. If you for sure want to use OD and you have lots of hills/mountains consider 4.56.
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mkirsch wrote: You need to keep in mind that the only thing changing ratios does for you is give you better acceleration off the line. People seem to think that it gives you "more power." It doesn't. The power available from the engine is the same, and it will take X power to move Y trailer in Z conditions no matter the gear ratio.
It`s not just acceleration, changing gear ratios allows the engine to operate in a different powerband. sometimes it`s that 3-400rpm difference that will take you from hunting between 3rd and 4th to cruising along in forth with no lugging of the engine.
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I'm not buying the part about changing Gears is just quicker off the line. My 4.7L 5 Spd Durango was 6000Lbs Towing with the Stock 3.55. A Stock 3.92 gives you 7500Lbs Towing Capacity. I just stuck a 4.10 Gear Set in and estimating now at 8000Lbs towing, although I would never exceed the 7500 rating since the Factory says that is all the Durango can handle with a 3.92. You still have to be able to stop.
Here are my Previous and New Speed/RPM Numbers recorded before/after.
Numbers with Stock 3.55 Ratio -- Numbers New 4.10 Gears and Trac-Loc
50 MPH = 1500 / 50 MPH = 1730 / 55 MPH = 1700 in OD
Should be a Major Improvement Towing my 5800 Lbs of loaded Wildwood.
I love the way it drives locally in the hills, stays in OD, doesn't Downshift, Torques it right up the hills. Engine now has full Cold Air Intake too. Local mileage instead of 9-14 mpg is up slightly, 12 - 15.6 so far. Need longer averaging since I just got it out of the shop yesterday.
mkirsch wrote: You need to keep in mind that the only thing changing ratios does for you is give you better acceleration off the line. People seem to think that it gives you "more power." It doesn't. The power available from the engine is the same, and it will take X power to move Y trailer in Z conditions no matter the gear ratio.
If you're able to haul the trailer in 3rd, save your money and haul it in 3rd. 3rd is 1:1, which always was top gear until they started putting overdrives in pickup trucks.
The power is the same however you'll have more torque to the rear wheels, allowing you to tow your trailer easier. Changing from 3.55 to 4.10 gears will give you ~15.5% more torque at the wheels.
* This post was
edited 02/21/08 11:08am by GoldHEMI *
GoldHEMI wrote: The power is the same however you'll have more torque to the rear wheels, allowing you to tow your trailer easier. Changing from 3.55 to 4.10 gears will give you ~15.5% more torque at the wheels.
This is correct. I want to add that most gas motors operate well below peak torque and horsepower when cruising the flat and level. By increasing the RPM the motor actually will make more power at a fixed speed. So with maybe 5% more torque from the motor and 15% from the gears the effect is very noticable.
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