HO 3.73 vs 4.1?

[silver billet]

There is so much talk about power off the line here. Are you guys really having trouble getting going? Are you really trying to rip off the line with 20k lb behind you? Sounds like a great way to mess up the 5er and everything in it!

I've never towed anything heavier than 20klb so is that just why I'm not complaining about power off the line?

No argument from me, that's why I've been saying the gear ratio is less important than many think it is.

I partly blame the J2807 standard for this, it exaggerates the differences in two otherwise identical trucks by several thousand pounds GCWR just due to how fast they can or cannot get off the line in first gear.

But in real life, that's far less of a problem. Almost nobody has trouble getting going, if they did they definitely wouldn't be able to pull at 60 either.

In real life, people want more power getting onto a freeway onramp (so city mph to freeway mph while already rolling quite fast), or passing a semi up a hill. And at that point your transmission is more than capable of putting your rpms where they need to be by downshifting, cancelling out the advantage of the rear axle - so only more engine torque/hp will help in these cases, hence the recommendation for the HO instead of the SO.

 

[AH64ID]

I know a hot shotter who went from a 2018 4500 with 4.10's to a 2022 5500 with 4.44's and the 4.44's are netting better empty mileage, and the pulling power difference is impressive. That's a guy who tows for a living. The power change from 18 to 22 isn't as drastic in the C&C and the transmission is the same. I don't believe he has any plans to go back to 4.10's in his next truck.

Looking at the drive ratios with the AS69RC and 3.73 vs 4.10 the 3.73's do have the gearing advantage one gear lower for 2nd thru 5th. That's the same as going from 3.42's to 3.73's. I really liked my 3.42's and had no complaints, but the 3.73's are just better.

 

[H3LZSN1P3R]

I know a hot shotter who went from a 2018 4500 with 4.10's to a 2022 5500 with 4.44's and the 4.44's are netting better empty mileage, and the pulling power difference is impressive. That's a guy who tows for a living. The power change from 18 to 22 isn't as drastic in the C&C and the transmission is the same. I don't believe he has any plans to go back to 4.10's in his next truck.

Looking at the drive ratios with the AS69RC and 3.73 vs 4.10 the 3.73's do have the gearing advantage one gear lower for 2nd thru 5th. That's the same as going from 3.42's to 3.73's. I really liked my 3.42's and had no complaints, but the 3.73's are just better.

I thought greg had the 4.88, him having 4.44 makes more sense, he does not seem to drive terribly fast which is where the 4.44 is better. Its all about keeping the RPM below 2k thats where it really starts drinking the fuel! Lol

 

[AH64ID]

I thought greg had the 4.88, him having 4.44 makes more sense, he does not seem to drive terribly fast which is where the 4.44 is better. Its all about keeping the RPM below 2k thats where it really starts drinking the fuel! Lol

Yeah, I don't recall what speed he said he runs at bobtail but I'm sure its the same in the 22 as the 18. With 4.44's 2000 rpms in ~65 mph.

 

[Thisnthat]

what's the reasonable top end speed towing on the 4.10s vs the 3.73s these days? guessing no measurable difference - at least not what "most" safely drive

many moons ago we had a 3.73 dodge 3500 and I think it was a 4.55 F550 (late 90s and early 00s and manual 5-6spds)...the F550 seemed too stressed for my liking on the interstate, 68-72 was about the max where I felt comfortable - empty or towing, always felt like the guy everybody was mad at for driving at or below the speed limit. any faster and it was like the ole 454s never being able to pass up a gas station

 

[AH64ID]

what's the reasonable top end speed towing on the 4.10s vs the 3.73s these days? guessing no measurable difference - at least not what "most" safely drive

2400 rpms is 86 with 4.10’s and 235/80R17’s.

Towing is whatever speed you’re comfortable at.

 

[Brutal_HO]

From a gear speed worksheet I've had laying around since forever.

Brutal gear-speed-calculator (version 1).xlsx

Gear-Speed Calculator Axle Ratio,3.73,Enter the axle ratio here,Axle Ratio,4.10,Enter the axle ratio here,Axle Ratio,3.73,Enter the axle ratio here Tire Specs,Tire Specs,Tire Specs Size,265.00,Enter metric tire size in MM here,Size,265.00,Enter metric tire size in MM here,Size,265.00,Enter metri...

docs.google.com

 

[timelinex]

Well guys I got the truck. I haven't had any climbs yet, but holy smokes the HO feels so much better than the SO already. Even when empty, flooring my SO felt anemic. Theres a reason i called it the fat pig. When i floor the HO , it actually moves! Which is surprising considering it's drw vs srw and heavier. I thought I would only see the HO difference under heavy load.

I'm excited to try it out and report back. Based on the speeds I go when towing , it looks like the 3.73 may be good RPM wise (25% @ 75-80, 50% @ 65-74, 25% @ 55-64)

 

[CdnHO]

That HO really pulls strong for a heavy truck.

 

[timelinex]

Well guys, I am back from a 1,000 mile trip and have some feedback. It was round trip from Phoenix, AZ to Durango, CO so there are ALOT of 6%+ grades up and down ranging from 55-75mph speed limits. I'm carrying a 20,000 lb 5er.

Here are my thoughts:

1. HO definitely makes a difference, but it wasn't as big as I thought it would be.
2. In normal city driving (35-55mph) I never found myself lacking and it definitely moved as fast as I would want it to.
3. MPG was 7.5
4. Previously, with my SRW SO, I would top out at 48-54 mph or so on the biggest up hills. This DRW HO tops out at 54-59 mph on those same hills.
5. There was one time in the middle of a hill where I had to shed a lot of speed because of traffic, and it basically crawled at 48mph+ (hill ended before it got past 53 or something)
6. Passing someone at 60+ is very difficult if there is ANY slope at all. Even at slight slopes, it just gains speed too slow.
7. In my previous rig, exhaust brake did a great job, but based on the engine/gearing I would basically have to go 55mph or slower for me to be in the right RPM range to work well on those BIG hills. In this rig, its at a PERFECT 60-70 mph or so. This is a huge deal for me as it keeps me completely off my brakes and feeling safe.

So the big disappointment is still not enough umph on slopes at highway speeds. I do want to point out though that overall I'm still VERY happy with the truck. Overall, I would have enjoyed more power maybe once every hundred miles. But the consequence would be driving 58 instead of 65 for a minute. Overall no big deal, I just wanted to let everyone know my experiences.

Without trying the 4.10's to make a direct comparison, I can't say for sure how happy or disappointed I am in the 3.73 vs 4.10 debate. However I would tentatively say I may be happy with the 3.73's considering the engine brake gearing matches up great for my purposes and the possible MPG implications. I usually don't care about MPG's, but if I'm already at 7.5mpg, I start caring. I wouldn't want even worse.

 

[CdnHO]

With a fiver that heavy a 4.10 would be a better choice. However the 3.73 will get the job done.

 

[gimmie11s]

With a fiver that heavy a 4.10 would be a better choice. However the 3.73 will get the job done.

100%.

For that heavy of a trailer I don't even know why anyone would consider the 3.73 option.

Im only towing 14k lbs, but my 4.10 HO DRW will go 70+ mph up any hill ive tried in CA, NV, AZ, WY, ID, CO, OR, WA, and MT.

That said, I still would have spec'd with MORE gear if they offered it.

 

[H3LZSN1P3R]

100%.

For that heavy of a trailer I don't even know why anyone would consider the 3.73 option.

Im only towing 14k lbs, but my 4.10 HO DRW will go 70+ mph up any hill ive tried in CA, NV, AZ, WY, ID, CO, OR, WA, and MT.

That said, I still would have spec'd with MORE gear if they offered it.

See this is where you have to figure out the vehicle use if the truck is a dedicated tow rig then yes i agree with you but if it tows less than 1/4 of the time like the avg camper does well it does not make sense to have the higher ratio to me, also factoring in if the truck will keep the stock size tires would sway the gear choice too.

 

[gimmie11s]

See this is where you have to figure out the vehicle use if the truck is a dedicated tow rig then yes i agree with you but if it tows less than 1/4 of the time like the avg camper does well it does not make sense to have the higher ratio to me, also factoring in if the truck will keep the stock size tires would sway the gear choice too.

I agree 100%... this is a good point.

 

[CdnHO]

See this is where you have to figure out the vehicle use if the truck is a dedicated tow rig then yes i agree with you but if it tows less than 1/4 of the time like the avg camper does well it does not make sense to have the higher ratio to me, also factoring in if the truck will keep the stock size tires would sway the gear choice too.

I am towing 21K just under 70 percent of my miles. The choice of rear axle ratio was a no brainer.

 

[timelinex]

I was looking for a private party (I save sales tax in AZ) 2022 Limited for a year or so. It was impossible to find one that wasn't asking way more than dealers. I'm guessing a lot of people overpaid during C19 and didn't realize prices plummeted. This one was an OK deal, it was a local car, good condition and I was sick of looking. It had everything I wanted except the gearing. So I jumped on it.

If I had a choice, I would go 4.10.... But after seeing the MPH even on the 3.73 I am not too upset about getting the 3.73.

 

[darrellr]

With a fiver that heavy a 4.10 would be a better choice. However the 3.73 will get the job done.

Why? I am still unclear how a 4.10 ratio will help you at all once you are above first gear. A 4.10 ratio in 6th gear will be very similar to a 3.73 ratio in 5th gear, roughly, I think. Just drop a gear with the 3.73 and all is good. It will be slower to get moving off the line, but after that it just won't matter much. If anyone has evidence (not anecdotes) to the contrary, I would greatly appreciate it being passed along.

 

[H3LZSN1P3R]

Why? I am still unclear how a 4.10 ratio will help you at all once you are above first gear. A 4.10 ratio in 6th gear will be very similar to a 3.73 ratio in 5th gear, roughly, I think. Just drop a gear with the 3.73 and all is good. It will be slower to get moving off the line, but after that it just won't matter much. If anyone has evidence (not anecdotes) to the contrary, I would greatly appreciate it being passed along.

RPM has little to do with why 4.10s are better at moving weight its not about how fast your rear end is spinning its about how easy it is to move yes with a taller gear you get more RPM but it also makes things easier to move. People think RPM matters but its only part of the occasion

 

[CdnHO]

RPM has little to do with why 4.10s are better at moving weight its not about how fast your rear end is spinning its about how easy it is to move yes with a taller gear you get more RPM but it also makes things easier to move. People think RPM matters but its only part of the occasion

It's all the lever principal. Also easier to maintain peak torque engine speed when moving at highway speeds. This is when the engine is running at itd most efficient. Of course it depends on how fast you run. I just put it in tow/haul and let the transmission do its thing.

 

[silver billet]

It's all the lever principal. Also easier to maintain peak torque engine speed when moving at highway speeds. This is when the engine is running at itd most efficient. Of course it depends on how fast you run. I just put it in tow/haul and let the transmission do its thing.

It's about torque multiplication. But your engine torque is multiplied by both your transmission and your rear axle, if both trucks are at the same mph using a final gear ratio of (say) 3.5, then it doesn't matter how they got there (transmission gear vs rear axle), your rpms will be equivalent, so will your torque multiplication.

Rear axle ratio is badly misunderstood around here and other forums.