dodge guy
Bartlett IL
Senior Member
Joined: 03/23/2004
View Profile
 Offline
|
parker.rowe wrote:mkirsch wrote:parker.rowe wrote:I'm not sure why people think the rear gear ratio only changes rpm/mph.
It increases torque multiplication to the rear wheels. It will tow more easily in all gears. It may allow towing one gear higher than usual
If the truck is in fact a 3.73 truck, it will make a difference going to 4.30's. Ford didn't offer that option for fun.
Yes, it will increase cruise RPM in 6th by 2-300 rpm. Might loose 1mpg unloaded. But as Fish stated you may gain mpg towing.
You know WHY it "tow more easily in all gears?"
Because the engine is running at a higher RPM at all speeds!
The engine produces more HP at higher RPMs, up to the peak of the power curve.
People think "gear ratio only changes rpm/mph" because that is precisely what it does.
If you were doing 60MPH at 2000RPM with stock 3.73 gears, you will need to rev the engine to 2305RPM to maintain 60MPH with 4.30 gears, or you will only be doing 52MPH at 2000RPM.
You still have torque multiplication happening.
For easy math, lets say you have an engine with a nice flat torque curve.
100ft lbs at both 2000 and 2300rpm.
Running in direct (1:1), also to make the math easier.
100ft lbs x 1 x 3.73 = 373 ft lbs
100 ft lbs x 1 x 4.30 = 430 ft lbs
The main benefit is not that it puts you at a different rpm closer to the torque peak...it is that you increase the torque multiplication in every gear.
Yes! A lot of people don’t understand that. They just think it makes it scream and use more gas, when it’s just not true.
On my V-10 Excursion I went from 3.73 to 4.30 and gained .5 mpg. Why? Because I was now able to use OD which it couldn’t before. It also made each gear more efficient.
Wife Kim
Son Brandon 17yrs
Daughter Marissa 16yrs
Dog Bailey
12 Forest River Georgetown 350TS Hellwig sway bars, BlueOx TrueCenter stabilizer
13 Ford Explorer Roadmaster Stowmaster 5000, VIP Tow>
A bad day camping is
better than a good day at work!
|
Cummins12V98
on the road
Senior Member
Joined: 06/03/2012
View Profile
Offline
|
MFL wrote:Cummins12V98 wrote:Jerry Said: "I use non ethanol premium fuel"
UH Jerry the OP is in KOMMIFORNIA and Non Ethanol is a non spoken word.
Oops...maybe not in Ka? Even in my area, pure premium is usually only available at top tier stations. I might add, that pure regular (non-ethanol) is even harder to find.
We are lucky in NW WA to have Cenex Farm supply that has Red Diesel and all three grades of non ethanol.
2015 RAM LongHorn 3500 Dually CrewCab 4X4 CUMMINS/AISIN RearAir 385HP/865TQ 4:10's
37,800# GCVWR "Towing Beast"
"HeavyWeight" B&W RVK3600
2016 MobileSuites 39TKSB3 highly "Elited" In the stable
2007.5 Mobile Suites 36 SB3 29,000# Combined SOLD
|
valhalla360
No paticular place.
Senior Member
Joined: 08/19/2009
View Profile
Good Sam RV Club Member
|
parker.rowe wrote:The main benefit is not that it puts you at a different rpm closer to the torque peak...it is that you increase the torque multiplication in every gear.
So assuming you aren't regularly in 1st gear and struggling, explain what benefit that provides over simply dropping down one gear.
Is it somehow unmanly to downshift?
The benefit really is keeping the engine up in the peak torque range with higher RPM because HP = Torque * RPM and HP determines how fast you can climb a hill.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV
|
mkirsch
Rochester, NY
Senior Member
Joined: 04/09/2004
View Profile
|
dodge guy wrote:mkirsch wrote:valhalla360 wrote:A deeper rear end won't do anything to help this.
At least not enough to justify the cost and inconvenience of roaring around like an old Army Jeep the rest of the time.
It most certainly will! It will let the truck pull in a different gear. On a gasser as little as 300rpm makes a difference to n towing at the top of one gear or the bottom of the next. It does indeed make a difference. That’s why different axle ratios are offered by the manuf.
Not anymore. Most HD pickup trucks only have one gear option these days.
Putting 10-ply tires on half ton trucks since aught-four.
|
parker.rowe
Delaware
Senior Member
Joined: 09/14/2015
View Profile
Offline
|
mkirsch wrote:
Not anymore. Most HD pickup trucks only have one gear option these days.
Not for gas trucks. Dodge offers 2 options, Ford offers 3. Gm is the only one that does not have an option. They haven't for a while iirc.
There are only 3 major manufactures of consumer HD trucks, and 2 of those offer different gear options, with increased tow ratings for deeper gears, for the gas trucks.
* This post was
edited 07/13/22 12:32pm by parker.rowe *
2015 Starcraft TravelStar 239TBS 6500 GVWR
1997 GMC Suburban K2500 7.4 Vortec/4.10
1977 Kawasaki KZ1000
|
|
|
blt2ski
Kirkland, Wa
Moderator
Joined: 03/15/2001
View Profile
Offline
|
parker.rowe wrote:mkirsch wrote:
Not anymore. Most HD pickup trucks only have one gear option these days.
Not for gas trucks. Dodge offers 2 options, Ford offers 3. Gm is the only one that does not have an option. They haven't for a while iirc.
There are only 3 major manufactures of consumer HD trucks, and 2 of those offer different gear options, with increased tow ratings for deeper gears, for the gas trucks.
Issue with the RA deeper us better, it helps MOST in first gear assuming everything else is the same.
BUT, with my GM 6.5TD, on a freeway grade of 3-5%, with the nv4500 I had, the 3.73 would have been the better RA ratio. As the grade got steeper, I dropped a gear, I could go to redline in next lower gear, same speed as 1800 in higher gear.....reality, I would assume a high percentage majority of us do not drive at WOT in the gear below. We do as I did in that truck, reduce rpm to 2700 to 2800, drive whatever that speed is. With the 3.73, I would have been going faster bt 5mph or so.
Same thing occurs in my Navistar, having 7 forward gears, reasonably space apart, I've pulled hills better that higher up/torque motors with fewer gears. Both of these in first gear, due to lower overall ratio times torque, out pulled a basically double HP/torque Dmax. 6.5 by an additional%grade before stalling at 20k lbs. The IHC with lowest power, 30% at 30k lbs due to an overall low around 45-1 vs effective ratio of 17-1.
Iff you want to talk 4% freeway grade speed, the Dmax at 320 HP more than left the 175/185hp of the IHC/GM behind.
Reality, a lower ra may or may not help in actual towing experience. Depends upon the situation, what you want that truck to do or behave.
Marty
92 Navistar dump truck, 7.3L 7 sp, 4.33 gears with a Detroit no spin
2014 Chevy 1500 Dual cab 4x4
92 Red-e-haul 12K equipment trailer
|
time2roll
Southern California
Senior Member
Joined: 03/21/2005
View Profile
Good Sam RV Club Member
|
valhalla360 wrote:parker.rowe wrote:The main benefit is not that it puts you at a different rpm closer to the torque peak...it is that you increase the torque multiplication in every gear. So assuming you aren't regularly in 1st gear and struggling, explain what benefit that provides over simply dropping down one gear.
Is it somehow unmanly to downshift?
The benefit really is keeping the engine up in the peak torque range with higher RPM because HP = Torque * RPM and HP determines how fast you can climb a hill. Sometimes to split the gears just seems better. Yes if changing the final drive was basically the same as a downshift it would be mostly pointless.
Six speeds sounds great but often it is a choice of 3rd or 4th going up a hill and the user may want gear 3.5
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675w Solar pictures back up
|
dodge guy
Bartlett IL
Senior Member
Joined: 03/23/2004
View Profile
Offline
|
valhalla360 wrote:parker.rowe wrote:The main benefit is not that it puts you at a different rpm closer to the torque peak...it is that you increase the torque multiplication in every gear.
So assuming you aren't regularly in 1st gear and struggling, explain what benefit that provides over simply dropping down one gear.
Is it somehow unmanly to downshift?
The benefit really is keeping the engine up in the peak torque range with higher RPM because HP = Torque * RPM and HP determines how fast you can climb a hill.
Unfortunately it doesnt work as simply as dropping down a gear. maybe with the new 8 and 10 speeds that may work, but with the 4 and 6 speeds dropping a gear can change where the rpm is. on my V-10 4 speed combo running in 3rd at a comfortable cruising rpm put me at 73mph. after going to 4.30 I could either cruise in 3rd at 67 at the same rpm or use OD and drop some more RPM.
It is far more than "just dropping a gear".
|
dodge guy
Bartlett IL
Senior Member
Joined: 03/23/2004
View Profile
Offline
|
time2roll wrote:valhalla360 wrote:parker.rowe wrote:The main benefit is not that it puts you at a different rpm closer to the torque peak...it is that you increase the torque multiplication in every gear. So assuming you aren't regularly in 1st gear and struggling, explain what benefit that provides over simply dropping down one gear.
Is it somehow unmanly to downshift?
The benefit really is keeping the engine up in the peak torque range with higher RPM because HP = Torque * RPM and HP determines how fast you can climb a hill. Sometimes to split the gears just seems better. Yes if changing the final drive was basically the same as a downshift it would be mostly pointless.
Six speeds sounds great but often it is a choice of 3rd or 4th going up a hill and the user may want gear 3.5
exactly. what is good for one person or combo may not be good for the next. a final drive swap tailors the vehicle to the person and load.
|
valhalla360
No paticular place.
Senior Member
Joined: 08/19/2009
View Profile
Good Sam RV Club Member
|
time2roll wrote:valhalla360 wrote:parker.rowe wrote:The main benefit is not that it puts you at a different rpm closer to the torque peak...it is that you increase the torque multiplication in every gear. So assuming you aren't regularly in 1st gear and struggling, explain what benefit that provides over simply dropping down one gear.
Is it somehow unmanly to downshift?
The benefit really is keeping the engine up in the peak torque range with higher RPM because HP = Torque * RPM and HP determines how fast you can climb a hill. Sometimes to split the gears just seems better. Yes if changing the final drive was basically the same as a downshift it would be mostly pointless.
Six speeds sounds great but often it is a choice of 3rd or 4th going up a hill and the user may want gear 3.5
Problem with this theory is the deeper rear-end is just as susceptible to this issue. Even with 4.3 it won't hold top gear when climbing a decent grade and as you say a half gear down would be better with older 3/4 speed transmissions in many cases.
The 6 speed is pretty good about this and the newer 8/10 speed transmissions really make the rear-end irrelevant except when towing at max GCVW.
|
|
|
