Differential Ratios

[rhagfo]

Originally Posted by John61CT

Yes invest energy into getting the best price selling this one, and finding a great deal on the next one.

The price differential will likely be lower cost, and the result more certain

I think this would be your best plan, just about what we are looking at.

[hornet28]

Originally Posted by fjr vfr

Just to clarify one thing, the higher the number means the lower the gear. A 3:73 ratio is higher geared than a 4:10 ratio.

At least one person here is knowledgeable about gears being lower or higher.

[Badbart56]

Originally Posted by hornet28

At least one person here is knowledgeable about gears being lower or higher.

I thought that was common knowledge.

[66joej]

Back when we used call them shallow ( lower number) and deep (higher number) rear ends. Don't know if that term is used anymore.

[fjr vfr]

Originally Posted by Badbart56

I thought that was common knowledge.

Not so in some earlier posts.

[fjr vfr]

Originally Posted by 66joej

Back when we used call them shallow ( lower number) and deep (higher number) rear ends. Don't know if that term is used anymore.

Seems I remember hearing those terms a very long time ago...I think?

[jsmith948]

Back when trucks had 3 pedals on the floor boards and 2 "clever levers" to change gears, low gear was sometimes referred to as "deep reduction".
Same with a semi's brownie box - sometimes they were a four speed box, but the low gear was not progressive it was called a " double under" or "deep reduction". Sorry for the nostalgia - I loved driving those twin stick trucks

[66joej]

Originally Posted by jsmith948

Back when trucks had 3 pedals on the floor boards and 2 "clever levers" to change gears, low gear was sometimes referred to as "deep reduction".
Same with a semi's brownie box - sometimes they were a four speed box, but the low gear was not progressive it was called a " double under" or "deep reduction". Sorry for the nostalgia - I loved driving those twin stick trucks

Wow that brings back memories. I used to put my left arm through the steering wheel to operate the 2 shifters in unison. And lots of double clutching. Used to call first/first the basement. Probably get ticketed for that now! No hands on the wheel.

[JRTJH]

Originally Posted by 66joej

Wow that brings back memories. .... Probably get ticketed for that now! No hands on the wheel.

You probably couldn't get your hands through the wheel (and around the air bag) on today's steering wheel.....

[77cruiser]

Originally Posted by jsmith948

Back when trucks had 3 pedals on the floor boards and 2 "clever levers" to change gears, low gear was sometimes referred to as "deep reduction".
Same with a semi's brownie box - sometimes they were a four speed box, but the low gear was not progressive it was called a " double under" or "deep reduction". Sorry for the nostalgia - I loved driving those twin stick trucks

Wasn't a fan myself, trucking company where I worked 78-89 had 3 of them 225 Cat's in Ford dump trucks. Liked the 13 speed road ranger no clutch required.

[fjr vfr]

I don't know how you guys remember all that?
I worked for International Harvester as a mechanic back in the mid 60's up until going into the army in 68. I worked in the motor pool and drove all manner of vehicle, but I hardly remember anything from that period of life.

It must be I'm getting really old or something. As the song goes...those were the days my friends, we thought they'd never end!
Well they did. It's better today...right.

[sourdough]

Originally Posted by fjr vfr

I don't know how you guys remember all that?
I worked for International Harvester as a mechanic back in the mid 60's up until going into the army in 68. I worked in the motor pool and drove all manner of vehicle, but I hardly remember anything from that period of life.

It must be I'm getting really old or something. As the song goes...those were the days my friends, we thought they'd never end!
Well they did. It's better today...right.

I think I'm pretty close with you. Drove dump trucks for a couple of years but couldn't begin to detail what I did or how I did it....but I had fun. And, like you, I hardly remember those kinds of details from that time....but then again, I ate breakfast out this morning......hmmm, was it bacon and eggs? Oatmeal? Ham? Oh well, I made it back and got to take my nap and feel better now!

[77cruiser]

Lotsa drugs back then too. I can remember stuff from the 70's - 80's now where I put that, what was I looking for 5 minutes ago.

[oldmanbill]

Did hot shot for several years with Dodge Cummins, ratio is the most misunderstood subject. If you have the torque to get rolling you are good. A little benefit with 4.10 with automatic but not with manual. Think about it this way. Going to 4.10 gives you about 1/2 gear lower ratio. Once rolling the gearshift controls the ratio. If it is a 5 speed, 5th is weak and heavy pulling is better in 4th, direct. My favorite is 6 speed with 3.73 axle. With 5 speed it is better to stay in 4th gear, with a 4.11 you must be in OD at highway speeds. I regularly pulled over 30,000 gross weight. Still have a '99 rusting in the back yard. You will do better with larger injectors and a chip for more power.

[John61CT]

Such heavy towing in very hilly territory, or slow usage like off-road, will favor the torque advantage of a lower-geared diff.

Especially with gas engines.

But reduce highway MPG if that's a concern.

[wkdoolin]

NOOO!!!! No. Do not change to a 4.10!!! Diesel engines are not designed for high RPMs I have 3 2004 dodges trucks, love the 5.9. Leave the rear alone and upgrade your transmission, take a look at FirePunk. There are others that are really good too. The best combo for the 5.9 is the 6 speed manual, auto has many issues and TC does not lockup very well. Get the advice of people that rebuild these 5.9s.

[Campy]

To the OP, how does the truck drive now? Changing gear ratio is a viable option depending on how the truck likes to perform. My 08 Duramax likes to pull at 2100-2200 rpms and will drag my camper with ease. Now the problem is with the 3.73 axle ratio it has the "normal" operating RPM's are 1800-1900 so the truck would really like a slightly higher RPM for dragging the load. I have asked around to see if simply going to a smaller tire diameter would get me the RPM's but it does not seem to add up. I have been considering a gear ratio change but the 4x4 thing is costly for the gears and install sets, I can do the work myself. I have a 6 speed Allison trans but have to manually limit it to 5 gears to get the performance the truck is looking for.

[chuckster57]

Originally Posted by wkdoolin

NOOO!!!! No. Do not change to a 4.10!!! Diesel engines are not designed for high RPMs I have 3 2004 dodges trucks, love the 5.9. Leave the rear alone and upgrade your transmission, take a look at FirePunk. There are others that are really good too. The best combo for the 5.9 is the 6 speed manual, auto has many issues and TC does not lockup very well. Get the advice of people that rebuild these 5.9s.

My truck came with 4:10 rear end. I have pulled my current and old fifth wheel up some very steep grades and ran it at 2600-2800 rpms with no issues. It’s actually better for a turbocharged Diesel to pull at higher RPMs since it keeps the turbo spooled up to max boost and moves air in/out of the engine. Gas engines have a higher rev limit.

[rickhz]

Originally Posted by chuckster57

4:10 is actually a higher ratio.

Hate to argue with the boss, but...

Higher in numbers, lower ratio.

Tall (high) gears have LOWER numerical numbers such as 2.79, 2.90, 3.00, 3.25. ... If you are cruising down the freeway at 60 MPH with 3.00 gears, in a typical high gear with a 1:1 output ratio, it simply means that the drive shaft (engine) is spinning 3 times for every 1 rotation of your tire.

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A lower (numerically higher) gear ratio, such as 3.55:1 to 4.10:1, provides more low-speed wheel torque, which means it takes less throttle to get the vehicle and the load it’s carrying or towing moving.

https://www.hardworkingtrucks.com/un...g-axle-ratios/

[kf4wsn]

Look At any Vehicle Spec and you will see that lowering the gear Ratio is the best way to increase tow capacity. Most people assume that it is mostly from increasing engine size only. The 4:10 is an Awesome Ratio for towing and makes it a breeze to pull. A Big killer is when people have to High a ratio like 3:73 and then add Taller tires and that makes the ratio even higher. I think that you will be most impressed with the added pulling power as well as the extra engine breaking. I don't think the dealers like to order trucks with the low ratios I had to special order mine and they would much rather sell one that is in stock or close by. But if you tow or Off road they are well worth the wait