2015 3.55 v. 3.73
12-14-2015, 11:35 AM
#12
Senior Member
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.
Of course, you can believe what you want, I will believe what I know...
12-14-2015, 10:52 PM
#14
9.75 gear set is the big boy know as it's much heavier duty with bigger bearings etc most 15 have a 8.8 except al 3.5 ecoboost and any truck with payload package gets 9.75 regardless of engine
12-15-2015, 10:07 AM
#15
Senior Member
Odd that the Ford parts website lists axle shafts for BOTH 8.8 and 9.75 for the 5.0 with HD payload and 3.73's, it lists the 9.75 for the 5.0 and 3.55's with no mention of HD payload and it lists the 8.8 for the 3.5 GTDI with 3.73's and HD payload among so many other variations.
12-15-2015, 12:02 PM
#16
Senior Member
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.
The small difference is not the difference between towing and blowing everything up, but there is a significant difference.
Again, you can have an opinion but to post it as fact is misleading to say the least. People come on here to get information and should know if you are correct or simply stating an opinion, and an incorrect one at that.
To the OP, I would not change gears as you would likely hit your payload max before you ever hit the towing limit anyway.
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12-15-2015, 07:20 PM
#17
The parts catalog is just a basic catalog went thru that when I bought 4.10s for my 05 I needed them for a raptor built before 12-10 but yet when my ford guy looked up the part number is said except svt package, I'm telling u as no 3.5 ecoboost has electric parking brake, as only the 8.8 has electric parking brake also the 5.0 and 2.7 all have 8.8 unless they have a payload package, the parts catalog makes zero since I went to 3 lots all 3.5 ecoboost had 9.75 axles
12-16-2015, 08:42 AM
#18
Senior Member
Odd that the Ford parts website lists axle shafts for BOTH 8.8 and 9.75 for the 5.0 with HD payload and 3.73's, it lists the 9.75 for the 5.0 and 3.55's with no mention of HD payload and it lists the 8.8 for the 3.5 GTDI with 3.73's and HD payload among so many other variations.
The 9.75HD is only avail with e-locker and a 3.73 ratio, and has higher Lube Capacity than the regular 9.75 and the 8.8.
Guess that's the one in the HD Payload trucks.
Last edited by brulaz; 12-16-2015 at 09:20 AM.
12-16-2015, 09:13 AM
#19
Opinionated Blowhard
My opinion. If you are flirting with the max towing capacity of your 1/2 ton truck, and you tow that weight consistently, then you need a 3/4 ton or larger truck to safely do the job. And by safely, I don't mean just physical safety, but mechanical safety as well.
As to the rear end ratio argument, I would say it's kind of pointless. If you tow every day with an average trailer on a 1/2 ton truck, then you have more than enough even with the 3.31 rear end. It called a transmission. There are six gear ratios in the current transmission, and soon there will be ten. Use the transmission to multiply your torque effort. For most drivers the rear end doesn't make that big a difference. What matters more is understanding how to use the transmission and its lockout feature to maximize towing performance when needed. Try it, it works.
As to the rear end ratio argument, I would say it's kind of pointless. If you tow every day with an average trailer on a 1/2 ton truck, then you have more than enough even with the 3.31 rear end. It called a transmission. There are six gear ratios in the current transmission, and soon there will be ten. Use the transmission to multiply your torque effort. For most drivers the rear end doesn't make that big a difference. What matters more is understanding how to use the transmission and its lockout feature to maximize towing performance when needed. Try it, it works.
12-16-2015, 10:26 AM
#20
Senior Member
As to the rear end ratio argument, I would say it's kind of pointless. If you tow every day with an average trailer on a 1/2 ton truck, then you have more than enough even with the 3.31 rear end. It called a transmission. There are six gear ratios in the current transmission, and soon there will be ten. Use the transmission to multiply your torque effort. For most drivers the rear end doesn't make that big a difference. What matters more is understanding how to use the transmission and its lockout feature to maximize towing performance when needed. Try it, it works.
if this is the case why would engineers bother to have different gear ratios?
Why not set up the trans to accommodate gearing and have a 1:1 gear in the rear?
The trans does not have the same effect as the rear ratio. In the trans you run through gears to get to the speed you want and stay within reasonable RPM while doing it.
The rear gears determine the pulling power at the wheels.
Lockout simply refers to locking the torque convertor as opposed to its normal operation which allows some slip as determined by RPM. It is a fluid coupler and thus requires a mechanical lock for a full lock. This is part of the reason why many prefer a standard transmission for towing, always in full lock so long as the clutch is engaged.
Attempting to compare the trans and rear gear as synonymous or one as superfluous is comparing apples to oranges or saying you have an apple and thus do not need water, respectively.
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