ib516 wrote: There is a reason the manufacturers increase tow rating and GCWR when equipped with the lower ratio (like 4.10).
More tq at the wheels, accessories (like water pump and fan) turn faster for more cooling, etc.
IMHO those are all good reasons for going with a lower ratio. The stock ratio for my Van is the 3.55 and the GCWR is 16K whereas with the 4.10 the GCWR is 20K and I get very close to the same mpg as other owners with the 3.55, but better performance since I can stay in OD a lot longer than them with the same drag towing. Often depending on the engine HP/TQ curve 400 rpms can really make a difference in towing performance. At my normal 2000K rpms towing I can tow a house, but at around 2500 to 2700 I can pull that house off it's foundation and is the really sweet spot for pulling with my engine
Larry
2001 standard box 7.3L E-350 PSD Van with 4.10 rear and 2007 Holiday Rambler Aluma-Lite 8306S Been RV'ing since 1974. TRAILER MODS
Your premise is correct; there is no 100% right or wrong answer. "It depends".
In general I like a TV to be geared where I can run the least RPM necessary while avoiding a downshift at every little hill. And that's a different number for every combination of vehicle and load.
Last diesel I had with 3.73; I liked it better after installing 35" tires. Effectively lowered the gear ratio. Got by with fewer revs in OD most of the time. Third gear became more useful in the mountains without high revs.
An earlier Dodge had the 3.54 which was ideal for that truck and my use.
6 liter gas, now that runs real strong with the 4.10 and I wouldn't want to tow with less.
YMMV.
Surveyor SV-234 >Equalizer> H3
Previously a fiver crew.
Think of it this way....start from the wheels and work toward the engine....2 identically loaded vehicles
It take a certain amount of rear wheel HP to move your vehicle. Transfer that through the rear end using different ratios and you get different torque the drive shaft has to deliver. The lower (numerically) the ratio the higher the torque because of the slower revolutions. So no matter what gear you are in the rear end ratio determines the torque the drive shaft needs to deliver. A 4.10 rear will results in less torque on the drive shaft than 3.42's. Less torque = less stress.
The 4.10 means more torque multiplication at the axle, and thus more torque applied by the tires to the ground, and thus more pulling power.
The driveshaft can take the torque. No need to reduce the axle ratio to 'save the driveshaft' on a truck with a basicaly stock motor and tire size.
If you take that diesel engine out of the truck and replace it with a lawn mower engine, there will be alot less stress on the driveshaft, but your truck won't be able to tow anything....
You don't say what your are towing or what you are towing it with so it is hard to give an answer.
Check the GCWR for your truck with your present gearing. If total weight for your rig is below that, I wouldn't worry much about durability. If you are above your GCWR, drop down to a ratio which gives you a GCWR that can accommodate your rig, particularly if you tow in the mountains. I went from 3.55's to 4.10's because most of my towing involves mountains where I live and haven't looked back. If the manufacturer says a lower ratio gives a higher GCWR, dollars to doughnuts it is because the transmission is the weakest link, or the clutch in the case of a manual.
Aside from that it is personal preference as to what ratio gives you the driving characteristics you like most.
"Never trust a man who has not a single redeeming vice" WSC
A 3.42 geared rig with 28" tires has the same shift points etc, assuming the same trans and engine, as a rig with 3.73 gears and 30" tires, which has the same shift points etc as a rig with 4.10's and 32" tires.........
In all honesty, one should gear a rig based on the trans too, ie a rig with 3.08 gears and a direct drive trans will turn the same rpms at 60 mph as a rig with 4.10's and a .75 OD, as will a rig with 4.74 gears with a .65 DOD!
So the reality is, there is NO correct answer, the best answer is it depends! and we are not disCUSSing the diaper variety of depends either!
The reality is, the best gearing is what puts you at your prefered freeway speed, say 60 mph, at X rpms, lets say 1800'rs, then figure out what tire radius you have, what your top trans gear is, and you can then figure out what is the optimum gear ratio for you. It can be different for different folks. Hence why personally, I would not like my dually DA combo with the 3.73 gears and the DOD 6 sp trans, the DOD is too high for the amount of driving I do with 90+% at speeds under 55. Yeah for those that drive 70, it puts the R's at 1500 or some such thing, but at 55, I am not sure I am doing anything but idle along. 4.33's or 4.56's would be a better gear set for me, with the 6 spd trans. With the 5 sp and a normal .71 OD, I am barely using OD as is, and lock it out most of the time! For me, having the overall lower gears would allow my setup to go from pullng a 23-24% grade in first gear and 20K lbs, before stalling, to over 30% which is an important number for me. BUT, as the tradeoff, my best freeway speed is about 60 mph for either option! I do NOT want a rig to tow or run down the road empty at 70 mph.
I also do not believe an axel ratio should allow one more GCWR, for all and many more reasons as I have described above. There should be a chassis GCWR, and a performance drivetrain GCWR where one can setup the drivetrain to there needs, not some engineer in Detroit etal, that thinks they know, well they might.....more than me. But, they do not know how I will use said twuck, hence, why I do not believe what they tell me, as I have stalled my share of rigs in 2wd on steeper hills, and blown up the auto trannies!
In the end, there is NOT a right answer, but one that will cause mucho debate on RV.net, and drive the poor moderator to drink................now where is that Dr Pepper I had?!?!?! not to mention my chocolate chip cookies!
marty
05 Chev CC D/A LS Dooley
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
00 Chev C2500, V5700, 4L80E, 4.10, base truck, no options!
92 Red-e-haul 12K equipment trailer
3 Single axle utility trailers
SoCalDesertRider wrote: The 4.10 means more torque multiplication at the axle, and thus more torque applied by the tires to the ground, and thus more pulling power.
The driveshaft can take the torque. No need to reduce the axle ratio to 'save the driveshaft' on a truck with a basicaly stock motor and tire size.
If you take that diesel engine out of the truck and replace it with a lawn mower engine, there will be alot less stress on the driveshaft, but your truck won't be able to tow anything....
This forum is great....people always puts words in your mouth. If you would like to believe 3.42's does not increase the stress on the driveline vs. 4.10's...more power to you.
blt2ski wrote: I also do not believe an axel ratio should allow one more GCWR, for all and many more reasons as I have described above. There should be a chassis GCWR, and a performance drivetrain GCWR
There can be only one GCWR and it is based on the weakest link, whether it is driveline or chassis. If an axle ratio changes the GCWR, it is because something in the driveline forward of the differential is the weakest link. Usually the transmission. If a different ratio does not change the GCWR it is because the weakest link must be somewhere in the chassis.
quabillion wrote: My truck has 3.73 gears right now, however I am going to change to 4.10 in about 2 weeks. Ill let ya know if I like it.
I doubt you would notice much difference as the gear ratio is quite close. I would leave the 3.73 in considering the cost of the gear swap vs real gain. A super charger would really perk up that 5.4 liter of yours.
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