2015 3.55 v. 3.73
12-09-2015, 08:08 AM
#1
Member
Thread Starter
2015 3.55 v. 3.73
2015 5.0L w/3.55 locking rear, says max towing is 9,100lbs but w/3.73 says max tow is 10,600lbs... is this as simple as a gear change or does Ford have an actual axle that's bigger?
12-09-2015, 10:55 AM
#2
Senior Member
axle same - just gear diff. in real life its very close...
12-09-2015, 11:15 AM
#3
Grumpy Old Man
Read the fine print. 10,800 tow rating on an F-150 4x4 SuperCrew with 5.0L engine, 18" tires, 6.5' bed and 3.73 axle ratio has GCWR of 16,200 pounds.
Same truck with 3.55 axle has GCWR of 14, 500 and tow rating of 9,100. The difference is only because of the axle ratio.
GCWR (and tow rating) is based on the pulling power of the tow vehicle, and pulling power depends partly on the leverage of the axle ratio. So yeah, an F-150 with 3.73 axle ratio can pull a heavier trailer than the identical truck with a 3.55 ratio, without overheating anything in the drivetrain and without being the slowpoke holding up traffic on steep grades.
So if you spend the big bucks to replace the ring gear and pinion in both axles, you would increase the GCWR of the truck. Tow rating is based on the GCWR minus the weight of the wet and loaded truck, so you won't have anywhere near 10,800 pounds of actual tow rating unless your wet and loaded truck including hitch weighs only 4,400 pounds (16.200 minus 11,800).
Note the caveat "wet and loaded" means full of gas and loaded with everyone and everything that will be in the truck when towing. But you would have an increase of about 1,700 pounds in actual tow rating.
Last edited by smokeywren; 12-09-2015 at 11:18 AM.
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weetay1 (12-09-2015)
12-09-2015, 12:27 PM
#4
Member
Thread Starter
Read the fine print. 10,800 tow rating on an F-150 4x4 SuperCrew with 5.0L engine, 18" tires, 6.5' bed and 3.73 axle ratio has GCWR of 16,200 pounds.
Same truck with 3.55 axle has GCWR of 14, 500 and tow rating of 9,100. The difference is only because of the axle ratio.
GCWR (and tow rating) is based on the pulling power of the tow vehicle, and pulling power depends partly on the leverage of the axle ratio. So yeah, an F-150 with 3.73 axle ratio can pull a heavier trailer than the identical truck with a 3.55 ratio, without overheating anything in the drivetrain and without being the slowpoke holding up traffic on steep grades.
So if you spend the big bucks to replace the ring gear and pinion in both axles, you would increase the GCWR of the truck. Tow rating is based on the GCWR minus the weight of the wet and loaded truck, so you won't have anywhere near 10,800 pounds of actual tow rating unless your wet and loaded truck including hitch weighs only 4,400 pounds (16.200 minus 11,800).
Note the caveat "wet and loaded" means full of gas and loaded with everyone and everything that will be in the truck when towing. But you would have an increase of about 1,700 pounds in actual tow rating.
Same truck with 3.55 axle has GCWR of 14, 500 and tow rating of 9,100. The difference is only because of the axle ratio.
GCWR (and tow rating) is based on the pulling power of the tow vehicle, and pulling power depends partly on the leverage of the axle ratio. So yeah, an F-150 with 3.73 axle ratio can pull a heavier trailer than the identical truck with a 3.55 ratio, without overheating anything in the drivetrain and without being the slowpoke holding up traffic on steep grades.
So if you spend the big bucks to replace the ring gear and pinion in both axles, you would increase the GCWR of the truck. Tow rating is based on the GCWR minus the weight of the wet and loaded truck, so you won't have anywhere near 10,800 pounds of actual tow rating unless your wet and loaded truck including hitch weighs only 4,400 pounds (16.200 minus 11,800).
Note the caveat "wet and loaded" means full of gas and loaded with everyone and everything that will be in the truck when towing. But you would have an increase of about 1,700 pounds in actual tow rating.
So I shouldn't bother swapping out gears?
Am I ever going to tow 10,000lbs? I don't know... but I will definitely be towing my jeep to different events around the country. The jeep itself is about 5k right now alone.
12-09-2015, 12:35 PM
#5
Senior Member
Good info!
Read the fine print. 10,800 tow rating on an F-150 4x4 SuperCrew with 5.0L engine, 18" tires, 6.5' bed and 3.73 axle ratio has GCWR of 16,200 pounds.
Same truck with 3.55 axle has GCWR of 14, 500 and tow rating of 9,100. The difference is only because of the axle ratio.
GCWR (and tow rating) is based on the pulling power of the tow vehicle, and pulling power depends partly on the leverage of the axle ratio. So yeah, an F-150 with 3.73 axle ratio can pull a heavier trailer than the identical truck with a 3.55 ratio, without overheating anything in the drivetrain and without being the slowpoke holding up traffic on steep grades.
So if you spend the big bucks to replace the ring gear and pinion in both axles, you would increase the GCWR of the truck. Tow rating is based on the GCWR minus the weight of the wet and loaded truck, so you won't have anywhere near 10,800 pounds of actual tow rating unless your wet and loaded truck including hitch weighs only 4,400 pounds (16.200 minus 11,800).
Note the caveat "wet and loaded" means full of gas and loaded with everyone and everything that will be in the truck when towing. But you would have an increase of about 1,700 pounds in actual tow rating.
Same truck with 3.55 axle has GCWR of 14, 500 and tow rating of 9,100. The difference is only because of the axle ratio.
GCWR (and tow rating) is based on the pulling power of the tow vehicle, and pulling power depends partly on the leverage of the axle ratio. So yeah, an F-150 with 3.73 axle ratio can pull a heavier trailer than the identical truck with a 3.55 ratio, without overheating anything in the drivetrain and without being the slowpoke holding up traffic on steep grades.
So if you spend the big bucks to replace the ring gear and pinion in both axles, you would increase the GCWR of the truck. Tow rating is based on the GCWR minus the weight of the wet and loaded truck, so you won't have anywhere near 10,800 pounds of actual tow rating unless your wet and loaded truck including hitch weighs only 4,400 pounds (16.200 minus 11,800).
Note the caveat "wet and loaded" means full of gas and loaded with everyone and everything that will be in the truck when towing. But you would have an increase of about 1,700 pounds in actual tow rating.
12-13-2015, 09:11 AM
#6
The difference between these 2 gear sets is so small as to mean nothing....100 rpm is all the difference you can expect and that's at any rpm in any gear. Check the gear chart if you do not believe me. Simply put there is no difference in towing capacity..none what so ever.
The 3.55 gear set WILL NOT cause the truck to overheat or slow up traffic or in hills nor will it over stress the transmission...this is just absolute BS.
So why does FORD rate them differently? Well, you can believe anything you want because no one really knows. People are reading the brochure and making assumptions that they do not understand and than passing them along as sage advice. I know my topic, I understand what it takes to tow and the only answer that I can come up with is marketing. FORD up sells the 3.73 gear set as either an outright 300 dollar option or you can step up to the FX4 which comes with the 3.73. Either way its more money in FORD's pocket for exactly the same truck. Check out CHEV or DODGE..they do not subscribe to this BS.
The 3.55 gear set WILL NOT cause the truck to overheat or slow up traffic or in hills nor will it over stress the transmission...this is just absolute BS.
So why does FORD rate them differently? Well, you can believe anything you want because no one really knows. People are reading the brochure and making assumptions that they do not understand and than passing them along as sage advice. I know my topic, I understand what it takes to tow and the only answer that I can come up with is marketing. FORD up sells the 3.73 gear set as either an outright 300 dollar option or you can step up to the FX4 which comes with the 3.73. Either way its more money in FORD's pocket for exactly the same truck. Check out CHEV or DODGE..they do not subscribe to this BS.
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weetay1 (12-13-2015)
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12-13-2015, 11:19 AM
#8
WindowGuy
Ford used to put a bigger axle on the HD Payload package, that included a 3.73. That option is no longer available. The differential you have is more than adequate. The time to have gotten the 3.73 was when you purchased your truck. It wouldn't have cost much. At this point, the benefits aren't justified by the cost.
12-13-2015, 03:55 PM
#9
Grumpy Old Man
Your opinion. I don't agree. And you won't find anyone with a PE in chassis engineering that will agree with you either.
That 5% difference in gear ratio will make a 5% difference in engine RPM at the same road speed. And depending on the HP and torque curves of your engine, that difference in engine RPM could make a difference in pulling power.
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12-13-2015, 09:44 PM
#10
Senior Member
Ford used to put a bigger axle on the HD Payload package, that included a 3.73. That option is no longer available. The differential you have is more than adequate. The time to have gotten the 3.73 was when you purchased your truck. It wouldn't have cost much. At this point, the benefits aren't justified by the cost.