Towing in overdrive

[Diamondpilot]

I am like Builder. My first diesel, a 7.3 4x4 Power Stroke had 4.10's. It would only do 16mpg at best. My next 3 trucks, a 2004 and 2006 Power Stroke's and a 2005 Dura Junk all had 3.73's and it was plenty of gear. My Dura Junk would get 20ish when it ran and my 2 6.0 Power Strokes with chips, intakes/filters, and exhaust mods get 23-24 empty on the highway and about 16-17 around town.

I have a gas truck with 4.10 gears but that is a totally different animal. The peak HP and Torque are way up the rpm range as mentioned before so it well suited for the work it does. This truck has just over 6,000 miles of which 5,000 plus have been either towing my 5,200# tractor on my car hauler or my 7,000# boat back and forth to the lake. Gas millage was not even a consideration with this truck, I wanted grunt.

Chris

 

[Builder]

I am like Builder.
Chris

You wish you were.

 

[Builder]

So which is better, behind my motor? My '01 Dodge is stock, with an auto, and 4:10. 3.55 was standard, 4.11 was option; I was used to 4.11 behind a 351 in a 89 Ford F250. I guess this truck is not all stock, it does have a 4" exhaust and a BHAF

So if I save my nickles and dimes for a ring/pinion swap, would it be 3.55 or 3.73? 3.73 would be right in the middle.

With 4.11's, it is a big change from OD to 3rd, especially on the freeway. At that point, anything over 50mph is really revving.

I run empty most, but tow my Kubota(4200 loaded with trailer), or a 7000lb mid sized 5th wheel.

3.55's would be great for fuel economy and juding by what you're towing below, you could easily tow those loads with 3.55's. An '01 Cummins with light mods wouldn't even break a sweat.

I gave up a lot getting the 4.11's. Best UI have ever got is 19mpg empty, running Sacramento to Tillamook Or for a Scout camp. I babied it to get that.

I have never researched it. I wonder if I could swap gears without changing the carrier? Have done it on Jeeps; when I went from 3.73 to 4.88, it required new posi's; ring gear was much larger. Back then, I think it was about $250 labor per axle, $250 for gears.

Not sure about that AAM axle, but if 3.55's were offered, you should easily be able to swap. I'm sure there's someone out there who perceives 4.10's to be superior and wants them. Maybe he would swap with you?

 

[FlaDon]

And that's why it's foolish to order anything over 3.73's with today's diesels. In fact, 3.55's would be more than adequate with a 650-700 ft lb diesel pickup making peak torque at 1400-1800 RPM. The less revolutions of the engine keeps it in its' max torque band. It economizes on fuel, too. I laugh at guys that get 4.10's with newer diesel trucks. Why do that? You're just wasting fuel and assuring your truck will be revved past its' sweet spot in many driving situations.

These guys with 4.10's, 4.30's & 4.88's behind a 650-700 ftlb diesel are actually running their trucks way past their sweet spot because they're over-revving their trucks down the highway. Sure, it helps launch the trailer, but who has ever run out of power towing a 12-16K trailer with a newer diesel? I never did, even with my stock 235/520 7.3L Powerjokes.

The other thing the numerically high gears hurt is boost. When the RPM's are way up, boost is lower because you can't "load" the motor. Diesels want to run down low in the RPM range, not lugging, but run low to make power & save fuel.

My 4800 has 5.38's and make ~18lbs boost max. I know several other guys running same trucks even with 4.10's making 25lbs boost. Sure, they can't launch like me, but they can pull a backhoe OK and once they're up to speed, they run lower RPM and waste less fuel. Their truck engine are more settled and mines revving anywhere past 45MPH. Only thing that helped me was installing an ES066-7B overdrive transmission to drop the RPM!

Can't argue with you on that. Get the truck geared for what it normally will see. For the tough grades/loads, that's what the tranny is there for. Keep the Diesel engine in the peak torque area and slow down if needed. Your wallet will love you for it.
4.10s are good if you have the OD to chop the RPM at highway speeds. But why kill your Diesel running it way past the torque curve peak if you don't.

 

[Diamondpilot]

You wish you were.

No, really I do not! Man I am lucky...

Cant say what I want here because of all the do gooders but you know how I feel about you!

Chris

 

[Builder]

Can't argue with you on that. Get the truck geared for what it normally will see. For the tough grades/loads, that's what the tranny is there for. Keep the Diesel engine in the peak torque area and slow down if needed. Your wallet will love you for it.
4.10s are good if you have the OD to chop the RPM at highway speeds. But why kill your Diesel running it way past the torque curve peak if you don't.

That's right on, Don. You have a lot of common sense.

There's a very good reason Dodge pickups are available with 3.55's. It's because they have the low end grunt to pull a load with 3.55's, not waste fuel and have longer B life than diesels like a 6L powderjoke that likes to rev.

Just your point that a gas engine like your 8.1L makes peak torque at a higher RPM should make it easy enough for any simpleton to understand why a diesel can get by with numerically lower gears...it revs lower and makes peak torque lower and usually has more torque to begin with.

Some people just don't get it.

I could not fathom a 350+ HP Duramax or a Cummins which has peak torque down ~1400RPM needing anything more than 3.73's to get the job done in a pickup. In a medium duty, maybe it would be acceptable to go higher for the bigger loads, but I know by ownership experience of 4.88's, they're lousy to drive.

4.10's, 4.30's or 4.88's would have a diesel pickup screaming down the road at anything over ~55, wasting fuel, running above peak torque and creating unecessary engine wear all the way. Only other reason to get them would be mauch larger than stock tires.

 

[Diamondpilot]

Do you guys get together and hold each other at night and tell Government Motors Stories?

You could whisper things like Allison, G80, large output shaft, 8.1, Dmax!!!

Glad you found someone to play your name dropping extensive knowledge game!


Now come on, that's funny... If you don't think so just get up and leave right now. (Larry The Cable Guy)

Chris

 

[FlaDon]

Do you guys get together and hold each other at night and tell Government Motors Stories to each other?

You could whisper things like Allison, G80, large output shaft, 8.1, Dmax!!!

Glad you found someone to play!


Now come on, that's funny... If you don't think so just get up and leave right now. (Larry The Cable Guy)
Chris

No. But I have taken a Diesel engineering course and I am Detroit Diesel trained/certified in maintenance and overhaul of engines both smaller and bigger than any truck uses. Plus Cummins, FM, and Cat maintenance. And I have slept at a Holiday Inn lately.

 

[Diamondpilot]

No. But I have taken a Diesel engineering course and I am Detroit Diesel trained/certified in maintenance and overhaul of engines both smaller and bigger than any truck uses. Plus Cummins, FM, and Cat maintenance. And I have slept at a Holiday Inn lately.

I like the Holiday Inn plug. So why did you opt for the 8.1 if you are a diesel tech?

Chris

 

[Builder]

No. But I have taken a Diesel engineering course and I am Detroit Diesel trained/certified in maintenance and overhaul of engines both smaller and bigger than any truck uses. Plus Cummins, FM, and Cat maintenance. And I have slept at a Holiday Inn lately.

Ouch, that's gotta hurt DP.

Imagine, a guy that has a far more extensive backround in diesels than a self styled diesel expert like "Diamondpilot".