2001.5 Axles, 3.54 vs 4.10 LSD

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JyRO-
Good points, but I disagree with one of them. The amount of fuel is proportional to the amount of air only if you are outputing about the same torque as engine speed increases. This would mean that your horsepower is also increasing. When we are comparing gearing we would be assuming the same engine horsepower output(same cruise speed)at different engine RPM's. If the engine RPM's are running 10% higher you would only require 90% of the torque compared to that required at the lower RPM (HP is proportional to torque times RPM). Theoretically at 10% higher RPM and at a constant HP output you would be putting in 10% less fuel proportional to air, but while putting in 10% more air, or using the same fuel rate regardless of RPM. The injectors would simply be fueling 10% less per engine revolution.

But Dodge don't use Theoretical engines, they use Cummins! The engine will have a sweet spot where it develops the best HP per rate of fuel consumption. If this is at higher RPM and lower torque, or lower RPM and higher torque I am not sure. But just lower RPM doesn't mean lower fuel consumption (again, assuming same road speed).

Pete Peterson-
I am planning on towing a boat trailer at about 10,000 lbs. This would be part time (but is reason for the truck) but mostly would be running empty (have 2 other trailers under 5,000 lbs).

 

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I have a 2001 ETH 4x4 which has the 3. 55 rearend and we just completed a 2000 mile trip pulling a 9k 5er and very few times did I have to downshift from sixth gear out on the highway running 65 to 70 mph. I would encourage any one to stay with 3. 55 ratio when buying the manual transmission. We just traded up on our 5er and am now pulling 10k dry weight and cant tell it makes any difference.
By the way my mileage averaged between 10 and 12 mpg towing at about 70 mph.

 

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Hey Ski Bum,

Welcome aboard!

Now..... about your order, did you actually get a (V)ehicle (O)rder (N)umber? I was under the impresion (from what I read here and what DC's 800# told me) that the 2001. 5 2500 can't even be ordered until the end of June or the first part of July. #ad


Thanks,

Mick2500

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2001 2500 ETH/DEE, QuadCab, 4X4, SB, LSD, 3. 54, SLT+, Sport, Intense Blue PC/Agate, Tow Package, Camper Package, 'DC' Bed Cover, Sliding rear window. Ordered 5/01/00... Cancelled 5/30/00... re-ordered 6/02/00... Cancelled again by DC 6/05/00
Gauges (EGT/Boost) and A-Pillar mount Here, 4" Exhaust on order.

 

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All these awesome mileage numbers is making me jealous. I always calculate mileage based on the odometer taking into account the error for the oversized tires. I can't beat 16mpg in town empty and on the highway I get more like 14 empty. I'd think with the 285's I've got I'd do better but maybe the width and weight are defeating any benefit of being taller.

I've been noticing all the posts about economy and I've come to the conclusion that the ISB differs greatly from truck to truck. Some people get 12, others get 20.

My 95 got 22mpg city, highway, empty, or loaded. Towing I got 21.

If it were me and I didn't have to tow a house, I'd get the 3. 54s.

I'm even considering an overdrive.

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1999 24V, NV4500HD, QC, 4x4, 3. 54, 8' Bed w/ Rhino Lining, 285/75R16s on 16x8 Eagles, Glasstite high topper

 

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I wouldnt trade my 4. 10's either. With 38" tall tires, at 75 mph, the Cummins is at 2000rpm. I still get good mileage in town, and pulling 9000lbs at 75 or 80 I get around 10mpg, passing PSD's like a Cummins powered rocket.

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99 2500 4x4,quad cab,lwb,black sport,4. 10lsd,5-speed,everything but leather,5" Tuff Country suspension lift chromed,3"body lift,38"Ground Hawg radials,16. 5x12 American Eagle wheels,K&N. VA box
2000 24' Weekend Warrior
97 Yamaha Banshee

 

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Hey, Ski Bum, can I take it from your handle that "snow and ice" handling is a big issue with you? If it is, you might want to consider the ARB lockers. Sure, they are expensive, but they give you complete driver control, something neither LSD nor other Locking axles can claim. Or, if you know LSD is what you want and Dodge won't give it to you in the ratio you want, Auburn gear and your local shop can convert you to LSD pretty quickly and for a reasonable price. I've got the 3. 54 axles on a 2001 ETH with 6 speed, and am happy. When I want more RPM's, I just drop to 5th. As to efficiency, my trip computer is indicating my truck likes LOWER rpm's. It's not just the wind speed either - even at a fixed speed, I seem to almost always get better mileage in 6th than in 5th. My optimum point has not yet been determined, but I think it is 1700 rpm or less, so I'm having to be careful not to lug the engine and wouldn't go this low on rpm for long term cruising except at very light load. Up to about 2000 rpm efficiency remains good; above 2200 rpm I'm definately getting lower mileage. JMO, but I think 4. 10's are for folks who ROUTINELY tow really heavy loads, or have gone to significantly taller tires. My opinion is based on the 6 speed; if you are getting Auto then make sure you listen to Auto owners, not me!

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2001 ETH, QC, LWB, 4WD, 3. 54, SPA Dual Gauge (Pyro & Boost)

 

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Hmmm...

I now have the 255 tires with the 4:10 rear end/auto/VA box---- and am consistently getting 19 city/hwy combo. Pulls the 22' TT like a rocket.

Kyle: how many miles on your rig???

 

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Kat check the speed limit signs west of Exit 439. Speed limit from millard to downtown in the morning raises to 80 you should know that!Hammer down!As far as the torque peak goes since it is flat,useing the bottom to middle part of it should give you the best mileage not the top part.

[This message has been edited by 6bbl (edited 06-16-2000). ]

 

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I believe the data your looking for is the brake specific fuel consumption (BFSC) - anybody know where to find the curve? This should tell you the most fuel efficient rpm.

Brian

 

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There are a number of factors effecting mileage especially when towing. When traveling to MM I noticed something with my 4x4,auto,3. 55s. At the higher RPM with O/D off the EGTs were lower. With O/D locked on the EGTs would climb. Higher EGTs means more fuel is being burned. Even though O/D should equate to better fuel econonomy when towing it didnt. I averaged 11mpgs down and back with O/D off and on at times. I need to install a boost gauge as well. This should give a better reading as to when the engine tends to be working.

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1999 2500 Cummins w/4spd auto,3. 54s,Quad Cab,SWB,4x4,Flame red ,all options less leather and radio controls on steering wheel,OEM color matched runningboards,DeeZee bedrails painted black,Power Vision Mirrors,OEM ventshades,Oem sill covers,OEM underrail bedliner,Isspro pyro,Westach temp,Painless wiring,RadioShack CB,Westin Black brushguard

 

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Hey Bennett,

You get your a$$ kicked alot, huh? HeHeHe #ad


I, like everyone else, get better mileage at 2000rpm or less. DC is full of crap as usual.

I have the 4. 10's and putting the 285/75's on increased my mileage by approx. 1. 5mpg. I would like to have the 3. 54's personally, because I hardly ever tow, and when I do, it's mostly on flat ground.

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1999 2500 QC 4X4 LB Auto 4. 10LS, Driftwood, CD player with Steering Wheel Controls, Power Driver's Seat, 275HP Injectors, Boost Regulator & Elbow, K&N Air Filter, Brushguard, Spray-in Liner, 285/75R16 BFG AT KO's, Nerf Bars, Black Diamond Plate Deep Well Tool Box, Mopar flat antispray guards (front and back)
2000 Yamaha Big Bear 400 4X4
NRA Member

 

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Mick 2500 (regarding ordering 2500):
Well... dealer had told me that he "for sure" was going to be able to have order accepted on 6/5. Then it was "for sure" on 6/12. Talked to him today. He was not able to enter the order after all. District manager told him likely in a couple of weeks or so.

No vehicle order number, no ship date, no order date, no f***ing anything. Seems Dodge would be just a little eager to take over $30K out of my hands, but I guess not.

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Wait'n for my 2001 2500QC, SB, 4x4, HO 6-sp, 4. 10 LSD, SLT++

[This message has been edited by Ski Bum (edited 06-16-2000). ]

 

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They got to give the guys that build it a vacation some time! the best way is to close the whole plant and give them all 2 weeks off! less scheduling problems through the rest of the year.

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• 98 ISB,QC,5spd,2wd,3:54lsd.
• 2000 Terry 305G 5th wheel

 

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Thanks Ski Bum,

Sorry you had to learn the same lesson I learned. #ad


I realize they get two weeks or more off at one time but hey... I ordered this thing on 4/28! The DC system responded 05/01/00 and then cancelled it on 05/30/00.

I'll be patient, I'll be patient, I'll be patient.

Mick2500

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2001 2500 ETH/DEE, QuadCab, 4X4, SB, LSD, 3. 54, SLT+, Sport, Intense Blue PC/Agate, Tow Package, Camper Package, 'DC' Bed Cover, Sliding rear window. Ordered 5/01/00... Cancelled 5/30/00... re-ordered 6/02/00... Cancelled again by DC 6/05/00
Gauges (EGT/Boost) and A-Pillar mount Here, 4" Exhaust, Here.

 

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Ski Bum,
I'm gonna go against most here and say the 4. 10's were the better choice. I would have done the same. Here's my reasoning...
Both my Rams had 3. 54's,one '99 5spd(245 tires) one '00 6spd(265 tires),with stock tires the '99 ran 200rpm higher than the '00 and got better mileage. The other factor people seem to be missing is the more 'work' the 3. 54's are making the engine do wether it's empty or loaded. The 3. 54's are gonna make your boost pressures run higher trying to maintain hiway speed,which in turn make your EGT's higher... . the higher the EGT,the crappier the fuel mileage. -Or- Slow down and drive 55(little fuel,little boost).

Everything is fine and dandy with the 3. 54's as long as you leave,or don't go any bigger than 265 tires. Once you go to 285's(like I did) the performance does kinda suck!
I don't want to change the 3. 54's to 4. 10's, but if anyone ever starts making a 3. 73 set for our Dana axles,I'll be first in line to get the bottom end RPM back.

I also want to add,I talk to alot of people and when they complain of crappy mileage,I probe their driving habbits. The majority don't have gauges so they don't know,but they drive with their foot in the pedal... uphill,or wrong gear... just not thinking of what they're doing. That's why I always tell people I drive by the gauges(or sound of the turbo) and with a little attention I do get good mileage. 18-19cty/20-21hwy,and that's not calculating the bigger tires.

-Mike

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'00 QC 2500 4x4, 6spd, LB, LSD, 3. 54, SLT, Dark Garnet, Agate, Camper, Trailer, Fogs, Clarion 6-disc, Smittybilt nerfs, Midland CB, Isspro pyro & boost, K&N Scotty Air, 3" pipe bomb, 2wd low, OEM tailgate lites, Tow hooks, DD stage II, BFG 285/75, 5. 9L R/T

A vulgar display of power!

[This message has been edited by MikeR (edited 06-17-2000). ]

 

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Again I must re-state my thoughts. Yeah sure the engine may be more fuel efficient at 2,200 rpms. But given the exact same road speed but lower rpms (at least to a certain degree lower, not a lot lower), the engine will be burning less fuel. At that lower rpm, it may be burning less efficiently, but it will be burning less! Less is less! Even if it is also less efficient, it's still less!

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Y2K 2500 Cummins ETC/DEE, SLT+, 4X4, Quad, LB, Intense Blue Sport, 3. 54 anti-spin, rear aux. springs (camper special), sliding rear window, all options except cab clearance lights including agate leather, totally stock, + a mpg increaser goodie

 

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What I read here is just what my friend and I went through last year prior to his retirement. As it worked out I bought my Y2K with 3:54 gearing and he bought his with the 4:10. Yep, we travel together and both pull 5ers but not large ones. They are 25 footers but these are the same units. We travel the west and real Mtns. often 7,000 to 10,000+ ft passes (both P/U's are five speeds with the same options). He wishes he would have gotten the 3:54. My mileage has always been better, most often we are filling up at the same time side by side (no figuring or fudging errors) and when it comes to pulling in the Mtns. he can not pull away from me very far or fast at all (VERY seldom out of sight). Just our situation/observations and remember we are only pulling 25' fifth wheelers not 10K units. Mileage for my unit, by pen and paper, runs 11. 6 to 12. 5 @ 70/75 mph, 2000 rpms. Which appears to be the same or very similar to the rpms some are running with 4:10 gearing and taller tires.

 

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I would get the 3. 54s unless you are going to do a lot of heavy pulling.
I have the 3. 55s, am recently retired and just bought an over 10k fifth wheel. I run 265 BFGs.
Last week I lost my 5th gear nut and learned a lot from the experience.
It seems I am lugging the engine down when pulling this load at 60/65 mph (around 1800rpm). Damn, I love stomping on it and passing other RVs in fifth gear going up hills but I am told this is bad for the drive train, even though the truck does it just fine. It seems I should drive faster, "It's OK honey, my mechanic insist on it!" or down shift much quicker.
The point is, I bought the truck to pull the trailer and now I wish I had the 4. 10s.
I also learned lots of us first time diesel owners don't drive our trucks the way a diesel should be driven when pulling heavy loads. They like to rev and the good spots aren't "felt" the same way as a gasser.
Watch the commercial trucks, they are always revving!
Mileage be damned, I want the truck to last a long, long time.
I guess my next set of tires will be stock to lower the gearing a bit... .
Ron


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'99 Quad long bed, 4x4, 5 speed, 3. 55 limslip, Rancho 9000/remote adjuster, DD stage IIs/boost module and elbow, 4" exhaust, gauges, stock filter, and a bunch of other stuff

 

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Ron your right, but at 60mph I'm in fourth. If I had 10K+ I would reconsider 75 mph also but I have fourth at 60 mph, even 65 for short periods with the 3:54 gearing and 265 tires. For what we pull and where we go the 3:54 gearing has turned out to be overall a little better, were both totally stock (for now). Besides that we have to have something to discuss or we would have to pick on our wifes and that we would both loose.

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Y2K RAM 2500 4X4 QC LWB Patriot Blue 5-Speed 3. 54 Anti-spin rear axle Trlr. Tow & Camper Packages & Westin Nerfs

 

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Idg,
I know what you are saying. When I was pulling my 19' travel trailer (about 6k)it was like a sports car. I would run 75 or 80 and pass everything on the road. My wife didn't even complain much as it seemed "safe".
The big fiver seems "safe" at 60 or 65 and I don't jam in and out of traffic much at these speeds. This is a bad speed for this gearing with my load. Fourth is too low and fifth is too high.
It sure was a lot more fun jaming with the trailer! I have to say it's a lot nicer now when we get there.
Happy Trails,
Ron