i assume higher is better?

Ivylog wrote:
Yes, back in the dark ages with only three speeds axle ratio was very important and when backing up it still is. If you have a 4X4 with a low range there is no reason to go with a high gear ratio. It's not going to hurt it to use the 4X4 on hard surface at slow speeds.

True if you don't turn, turning on dry surfaces in 4x4 with a heavy load puts a horrible strain on the drive train.
That's when manual hubs are handy.

OP, the higher the rear gear number the better it will pull and thus greater towing capability. Your logic is dead on the mark.

Ivylog wrote:
I'm one of the "Some will say with the 6 speed trany, Rear gears don't mean anything"... well not much. Yes in first gear it's a little harder to get moving but with a torque converter you will never notice the difference. By not using 6th (some of the time) you will have a a higher gear ratio (more RPMs/torque). The biggest problem is in reverse which has a ratio closer to 2nd and backing up a hill will heat the torque converter up quickly and IMHO the reason for the big difference in tow ratings.

Yes, back in the dark ages with only three speeds axle ratio was very important and when backing up it still is. If you have a 4X4 with a low range there is no reason to go with a high gear ratio. It's not going to hurt it to use the 4X4 on hard surface at slow speeds.

You also do not need 15% tongue weight... 10-12 is enough as long as you do not put two Honda generators in the back and then wonder why it's wanting to wag the dog.:S

The GM, and Ford engineers rate the lower rear gears to have a much higher towing capacity than they do the higher rear gears. Personally I tend to believe them. And towing in the mountains. I want the lowest gear. Often I am in first gear. Especially coming down.

It's about the overall gear ratio between the back of the motor and where the tire hits the pavement.

In the old days of 3 speed transmissions, there wasn't much option to match the ratio to the need. They had to provide for the worst case scenario but that meant running at higher RPM than needed much of the time. With modern 6-8 speed transmissions, the tranmission can match the gear to the need.

While it's always baffled me why reverse is roughly equivilent to 2nd gear, I've never seen someone burn up a transmission backing into a spot.

I say keep it close to 5000 pounds dry.

I'm one of the "Some will say with the 6 speed trany, Rear gears don't mean anything"... well not much. Yes in first gear it's a little harder to get moving but with a torque converter you will never notice the difference. By not using 6th (some of the time) you will have a a higher gear ratio (more RPMs/torque). The biggest problem is in reverse which has a ratio closer to 2nd and backing up a hill will heat the torque converter up quickly and IMHO the reason for the big difference in tow ratings.

Yes, back in the dark ages with only three speeds axle ratio was very important and when backing up it still is. If you have a 4X4 with a low range there is no reason to go with a high gear ratio. It's not going to hurt it to use the 4X4 on hard surface at slow speeds.

You also do not need 15% tongue weight... 10-12 is enough as long as you do not put two Honda generators in the back and then wonder why it's wanting to wag the dog.:S

nephi007 wrote:
Howdy. Given two identical tow vehicles but with different gear ratios where one has a higher one than the other how does that factor into the towing capabilities issue?

Examples, using a F150 of my vintage.
A 3.55 ratio is higher than a 3.73.
A F150 with a 5.4, 18 inch tires and 3.55 rears is rated to tow 8000lbs.
A F150 with the 5.4, 18inch tires, and 3.73 rears is rated to tow 9000lbs.

Does tire size make a difference? Yes. A F150, 5.4, 17 inch tires, and 3.55 rears is rated to tow 8500lbs

Same with a 3.73 is rated at 9500lbs.

Some will say with the 6 speed trany, Rear gears don't mean anything. But they really do. GM example. Suburban with 3.08 rears with a 5.3, 6 speed, tow max is 5000lbs. Same vehicle with 3.42 rears, tow max 7000lbs. 2000lb is a good bit of difference.

Ok I am taking the following from the owners manual for our truck: 2013 Silverado 1500 4 wheel drive short bed 5.3l V8 K5L HD Cooling Pkg axle ratio: 3.08 max trailer weight 6700 lbs GCWR 12,200 lbs. Our prior trailer was a 2007 JayFeather Lite 218 with a GVWR of 4000 lbs which this truck towed adequately. Yes I am in the market for a bunkhouse trailer with a walk around queen bed. Its me, wife and 12 year old daughter. The truck has a load carrying capacity of 1583 lbs. Assuming we weigh total 550 lbs with nothing in bed of truck, 100 lbs for the 4 point equalizer, a full gas tank of 22 gallons x 6 lbs per gallon=132 pounds I believe (from what I have read here) is the I need to find a trailer with a GVWR of 6100lbs or less because 6100 lbs x 15%=915 hitch weight ( I am ignoring dry weight of trailer which is a useless number I have read here). Anyway does any of this make sense?

Well a 2013 f250 gas will have a higher towing capacity with the lower gears (numerical higher ). The 3.73:1 have I think 12500 lbs were the 4.10:1 have around 15000 lbs.

Usually the lower gear will have a higher towing capacity.

But I have also driven a few semi trucks with 2.94s with a gross weight of 80000 lbs. And there pulled the hills just as good as a truck with the 3.58s

It would help a LOT to know the tow vehicle, engine, and such. Model year, if you know if it has a 2001 4 speed or a 2015 8 speed, it makes a HUGE difference !

Diesel actually will run better at lower RPM's than a gas engine. So 3.73:1 might be ideal with a diesel, while 4.10:1 might be good for a gas engine, and 4 speed auto.

My 1975 F-350 had a 3.73:1 ratio and 460" engine, so a lot of power. By running the 3.73:1 ratio, I did not turn the engine a lot faster than required to keep the load moving at 60 MPH.

I have a van now, with a V10, 10,000 GVW (14,050 GVWR) and it turns much faster than it need to for the loads on it. Gas mileage at 65 MPH is really bad, but at a slower RPM, such as going 55, it gets better mileage. It is a 2001 Shuttle bus, with 4.68:1 rear axle ratio.. Given that the V10 has lots of torque, I would be much happier with 3.73:1 ratio. Yet the 4.68 was selected because most E-450's have a 11' tall body that is 8' wide (80 square feet of air to push out of the way) and are typically much closer to 13,500 pounds GVW. I only have a 4 speed, while newer E-450's would have a 5 speed, and improved MPG.

So lets say that you have a 5.4L V8, 7,000 pound trailer, and 4 speed auto. With a 3.73:1 ratio, at 65 MPH, your truck would be running around 2,400 RPM. If that is changed to a 4.10:1 rear axle, then around 2,600 RPM. This will cause the engine to be able to make more HP at the higher RPM band, while also consuming more fuel. . So 'higher' is not better if you are the one buying the gas.

Yet if you take this to the extreme, and say have a F-150 with 3.08:1 rear axle, you might be turning 1,800 RPM in overdrive at 65 MPH, and constantly needing to downshift to drive to bring RPM back up to 3,000 to gain some speed again and again. If the transmission is 'hunting' from overdrive to drive and back over and over again, it is best to lock out overdrive, to prevent all that extra shifting for a while, until headwinds are less, you start downhill, or something changes.. .



Good luck,

Fred.