Truck differentials: 3.73 vs 4.10

mpeastend · 01-21-2011, 02:30 PM

I'm in the market for a new 3/4 ton, probably Chevy/GMC 2500HD or Dodge 2500 (regular cab, long box, 4WD, gas engine). You seem to gain quite a bit in towing capacity with a 4.10 rear vs the 3.73. As an example, the GMC goes from 9,900 lbs to 13,000 (with the ball hitch).

Does anyone here know how much mileage I'd be giving up by using the 4.10? The truck is strictly for towing a 24 or 28 ft enclosed trailer to the track so mileage can get important in the long run, especially with gas prices creeping up. Any resident truck experts have real world experience with this issue?

Thanks, Mike.

Rednine11 · 01-21-2011, 04:24 PM

i dont claim to be an expert at anything but I'd stay with 3:73's
4.10 makes the engine wind pretty tight and kills fuel mileage'

Had 4:10's in HEMI Cuda

Laneco · 04:43 PM

For towing, I pretty much dig the 4.10 with a four speed auto, though 3.73 with an older 3 speed auto in a truck works well and is just about perfect with a four speed auto on a V8 powered car.

The reason I would go with the 4.10 has to do with the final drive ratio which must include the tire size. Trucks use big tires. When you compare the actual distance the wheel travels per revolution of the drive-shaft, between a 3.73 in a car and a 4.10 in a truck (with car versus truck tires) you're closer than you think.

This is a neet little comparison chart. You can put in your calcuations and compare them side by side. Take something you KNOW and compare it to the vehicles you are considering to get an idea of the RPM you will be turning. Also, remember to consider the power band of the engine you are buying. A diesel makes makes tons of low end torque and can often take a taller rear gearing where with the gas engines, maybe a little steeper (toward the 4.10) will work better to put the engine in the power band.

Gear Ratio Calculator

Also, the huge killer when you are towing a trailer is wind drag. Tall trailers really kill the mileage, especially when you pick up even a few MPH. Keep the speed down and you will really improve your mileage with a tall trailer.

angela

afterburn 549 · 01-21-2011, 06:12 PM

If you are using your truck for a truck....4:10 is the only way to go..

mpeastend · 06:49 PM

Thanks to all for your answers!

Angela, wow, that's exactly what I'm looking for! Thanks so much! It's actually so detailed I can't plug in all the numbers until I find out some more values but it's what I need. You are right on about the placement of the powerband in regards to cruising rpm. GM & Dodge publish max hp & tq figures w/corresponding rpms but that doesn't tell me about the size/shape of the powerband. I will make educated guesses about them based on their stats and your calculator.

I was leaning towards the 4.10 for towing ease as I wasn't planning on doing the big wheels thing. I'm concerned about mileage on a 600 mile journey...would it be really off? I've done research on the 'net and come to two schools of thought:

1) The motor would always be spinning faster with mileage suffering but by how much is too variable to put a value on it. Most think that at a given rpm in top gear, the 4.10 would always be about 5mph slower and would have to spin approx 400-500 rpm quicker to keep up with a 3.73 & thus fuel consumption would go up.

2) Although the motor would be spinning faster, under towing situations, the motor would have to do less work/be less stressed and would therefore return better mileage. The throttle plates would be open less & less air/fuel required (less cylinder pressures) to do the work required even though the motor would be spinning faster. *Note* They were only indicating this for towing situations, since unladen it would probably just be based on engine rpms, the higher being the loser in mileage.

Joeaksa · 01-21-2011, 06:52 PM

If you are going to be towing much, get a Dodge 2500/3500 with the Cummins diesel. Otherwise buy stock in an oil company... you will need it.

LWJ · 01-21-2011, 06:56 PM

Not technical but I would think a racecar and trailer wouldn't weigh much. If you have a reasonably light trailer, the taller gears wouldn't be an issue. I know the camping trailer guys usually default to two wheel drive and diesels.

Larry

kaisen · 01-21-2011, 06:58 PM

Yes, that's correct. A 4.10 is not better or worse than a 3.73, it's just suited for a little different work. A 4.10 will pull better in top gear at, say, 60 mph where a 3.73 may pull better at 70mph. If you're going to be towing at 70mph all the time, then a 4.10 might be the wrong choice. Just an examples, there's much more to it as Angela pointed out. Tires, power curve (torque peak, area under the curve), transmission gear ratios, etc.

With the GM 6.0L and 6 speed automatic, it's not as important. The difference between 5th and 6th gear isn't great, so even if the 3.73 forces a drop in gear, it's basically like a 4.10 in 6th (if that makes sense).

A 4.10 might make a numeric multiplication of torque/force, but won't make up for the difference in the power curve. In other words, a 4.10 at 75mph may push the revs higher than peak torque. You want to pull at peak torque.

FYI, a Duramax diesel's ONLY gear choice is 3.73. Think about it. If a 4.10 were automatically 'better', wouldn't they offer that choice? And if 4.10 is great, why not 4.56? Etc, et al. It's a system. And there's a lot more involved than just the final gear ratio.

Radioactive · 01-21-2011, 06:59 PM

Don't forget the Chevrolet has a 6spd with a pretty low 1st gear you may want to take a closer look. If you only tow with the truck and nothing else then maybe the 4.10 but if you don't have a lot of mountains and not pushing the weight limit I would go with the 3.73

chapo · 01-21-2011, 07:13 PM

4:10 is the way to go with a gas motor. my last diesel ford had 4:10s and they were a little steep for the diesel. My new one has 3:73 and they are good. stock tires though. If you go up in tire size, definitely 4:10s for gas.

mpeastend · 01-21-2011, 07:15 PM

Larry: I'm thinking a 24-28 ft enclosed steel trailer w/2700 lb car & lots of gear will be about 8500-9000 lbs. The empty weight is at least 4K if not more.

Joe: I'm a big believer in diesels, despite the extra cost involved. I looked into the cummins' since I have an opportunity to get one at a good price through my union. I figured let me just check on how cummins is doing with their new 6.7L that replaced the gold standard 5.9L. Holy cr*p! I almost fainted when I saw all the bad stuff on the internet about this motor. It's like the Ford 6.0L, & more specifically, like their interim 6.4L navistar nightmare all over again! There are class action lawsuits, people are pissed about never ending regen cycles, crappy mileage, check engine lights coming on constantly, going back to dealers 2, 3 & 4X a month. It goes on and on. I was really shocked.
Apparently, the diesel particulate filter, the EPA & diesel exhaust fluid are tools of the devil. There is an entire cottage industry springing up to circumvent the DPF & regen cycles by replacing the DPF with a test pipe & plugging a computer into the wiring harness which tells the ECM that all is well. Of course none of this is legal for the street, but the motors run great after that.
The only motors that haven't gotten alot of bad press on the internet are the Duramaxes. The verdict is still out on the new in-house Ford motor, too new, can't find any problems yet that anybody's posting.

mpeastend · 01-21-2011, 07:27 PM

Kaisen: You're absolutely right. You basically expounded on what Angela said. The only thing is, I don't think I'll be able to answer those questions on paper prior to buying the truck. I don't think that type of data is available. I'd have to be lucky & find somebody in that position already who drives a truck in those conditions & can answer that question.

Radioactive: Was only planning on using the truck for towing.

Chapo: Was leaning for the 4.10, almost convinced now. The tires I wanted were the 265/17 all terrains they offer. I'm sure their rolling radius is slightly larger than the bone stock 245/17's but I have no interest in huge tires. Thank you for the input.

Thanks to all for the feedback, much appreciated!

kaisen · 01-21-2011, 07:28 PM

Quote:

Originally Posted by mpeastend

Larry: I'm thinking a 24-28 ft enclosed steel trailer w/2700 lb car & lots of gear will be about 8500-9000 lbs. The empty weight is at least 4K if not more.

I just sold my 24 ft enclosed V-nose steel-frame trailer with all the heavy-duty options that would make it heavier and that trailer weighed 3450 pounds. Obviously a 26 or 28 ft would get close to 4K.

I would buy a diesel for that kind of load. Not just weight, but aero load as well. Even the excellent GM LSx gas motor is barely enough for a 8-9K tag with that kind of aero load.

Otherwise, you'd better be considering the 4.10 gear, and ONLY the 4.10 gear. With the 3.73 you'd never even see 6th on flat land.

Dantilla · 07:34 PM

I have a 2001 Chevy K2500HD with the 6.0 litre, 4-sp auto, and 4:10 gears.

The tires are a bit larger than stock, but no lift kit- 285/75/16.

Highway cruising while empty gets about 14 mpg, prolly 12 around town. Loading it up pretty heavy doesn't affect milage as much as one would think.

The only time I would rather have 3:73 is during my semi-regular run down to the Portland area, when I don't need to carry much, and I-5 is pretty flat along that route. Whenever I have a load, or am towing, I'm glad I have the 4:10 axles.

The race car set-up is pretty light, as I have a 1500lb flatbed trailer, and my car is an ITS class 944.

kaisen · 01-21-2011, 07:34 PM

I towed this trailer with a couple different trucks. It's only 24ft. The only one that could handle the weight/aero without significant strain was a Duramax. I don't currently own a Powerstroke or Cummins, but have in the past, and I'm sure they would have done a fine job too. I even towed this with a 1999 GMC 454 Vortec with 4.10 gears and it didn't have the balls.

chapo · 01-21-2011, 07:35 PM

My buddy has a f-150 xtra cab 4.6 liter and put the same tires I run on it, the Continental 275's on 18 inch rims. His truck is dog slow now. Diesels don't mind to be lugged a little, the turbo covers it.

kaisen · 01-21-2011, 07:38 PM

Quote:

Originally Posted by Dantilla

I have a 2001 Chevy K2500HD with the 6.0 litre, 4-sp auto, and 4:10 gears.

The tires are a bit larger than stock, but no lift kit- 285/75/16.

Highway cruising while empty gets about 14 mpg, prolly 12 around town. Loading it up pretty heavy doesn't affect milage as much as one would think.

The only time I would rather have 3:73 is during my semi-regular run down to the Portland area, when I don't need to carry much, and I-5 is pretty flat along that route. Whenever I have a load, or am towing, I'm glad I have the 4:10 axles.

The race car set-up is pretty light, as I have a 1500lb flatbed trailer, and my car is an ITS class 944.

Your tires effectively make it equal to a stock 245/75-16 with a 3.73 gear. Your 285s make the 4.10s a wash.

And the new 360hp / 380 ft-lb VVT 6.0 and the new 6 speed auto make a non comparison.

Dantilla · 01-21-2011, 07:44 PM

Quote:

Originally Posted by kaisen

Your tires effectively make it equal to a stock 245/75-16 with a 3.73 gear. Your 285s make the 4.10s a wash.

And the new 360hp / 380 ft-lb VVT 6.0 and the new 6 speed auto make a non comparison.

Thanks for the info. In 2001, the gas 6.0 was good for 300 hp.

Another useless tidbit: The truck now has over 185,000 miles, and runs as new.

masraum · 01-21-2011, 07:49 PM

I'm not sure that I can really add much. As has been stated, these new trucks are coming with nice transmissions, tall tires need more gear. I recently rented a truck to drive to my mother's in FL, rent a trailer, and bring some stuff back from her house. It was about 1150 miles round trip. I rented a truck from Enterprise, it was an F250 superduty with a diesel. It got decent mileage on the way there running 75mph, I think 19mpg. I can't remember what it got on the way back, but it was just a small uhaul trailer, 8' long x 5' tall. You could hardly tell the trailer was there. If I was going to be towing, I can't see getting anything but diesel.

kaisen · 01-21-2011, 07:51 PM

Quote:

Originally Posted by mpeastend

The only thing is, I don't think I'll be able to answer those questions on paper prior to buying the truck. I don't think that type of data is available.

What type of data? I have all the data you'd need on the truck to do the math.

The L96 (6.0L) motor with VVT is pretty amazing in that it makes 380 ft-lb peak @ 4200 rpm, but makes over 300 ft-lb from 1200rpm to 6000rpm, and more than 350 from 2500 rpm to 5500 rpm. So for a gas NA motor, it's a pretty flat torque curve.