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Open Roads Forum  >  Tow Vehicles

 > Too low of a gear ratio?

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mkirsch

Rochester, NY

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Joined: 04/09/2004

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Posted: 02/17/11 08:02am Link  |  Print  |  Notify Moderator

Humor me for a few minutes here...

It baffles me why someone would think that a mid-2000's Dodge 5.7 Hemi pickup with 3.55 gears works well for pulling an 8000lb trailer in the Rocky Mountains, while someone with the same engine and 3.92 gears thinks it "struggles" on the flat with a similar trailer.

Simply put, the Hemi does NOT have enough power to pull an 8000lb trailer in overdrive with EITHER gear ratio, except downhill with a tailwind.

In 3rd gear, the 3.55 truck is running at about 2800 RPMs. Tolerable.

On the other hand, the 3.92 truck is running at about 3200 RPMs. That's getting a little loud.

The people with the 3.55s leave the truck in 3rd and have plenty of power for most conditions. On the other hand the 3.92 drivers are trying to get the truck back into overdrive all the time, so it's grunting, and struggling, and shifting frequently.

* This post was edited 02/17/11 10:16am by mkirsch *


Putting 10-ply tires on half ton trucks since aught-four.

mich800

Pontiac, MI

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Posted: 02/17/11 08:15am Link  |  Print  |  Notify Moderator

I do not think the Hemi was offered until the early 2000's. But I agree with the rest. Gearing is a compromise. The only time I ever got into OD with my Ford 5.4 was maybe going downhill. But I did not have a problem wringing it out on the hills if that is what it takes.

big dave

Soldotna, Alaska, USA

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Posted: 02/17/11 08:34am Link  |  Print  |  Notify Moderator

mich800 wrote:

I do not think the Hemi was offered until the early 2000's. But I agree with the rest. Gearing is a compromise. The only time I ever got into OD with my Ford 5.4 was maybe going downhill. But I did not have a problem wringing it out on the hills if that is what it takes.

Chrysler built a few hemi engines during World War 2 but none ever went into production. One developed over 3,000 h.p in a V16 configuration. The first hemi mass produced for an automobile was Introduced in the fall of 1950 as a 1951 model, the Fire Power 331 V-8 was offered as on option in the Saratoga (except for the coupe models), while it was standard in the New Yorker and Imperial.


Read more: http://wiki.answers.com/Q/When_was_the_hemi_introduced#ixzz1EEMk4JCb


Dave & Rose C
90 Safari Ivory 34' DP
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skipnchar

Topeka or somewhere else

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Posted: 02/17/11 08:37am Link  |  Print  |  Notify Moderator

Sounds like you believe (and I agree) that you have too HIGH a gear ratio. The REASON some use economy gearing like 3.55 or even higher yet like 331 instead of towing gears like 4.10 is because towing isn't a big priority with about 80% of the trucks on the road. They're built for and used for towing groceries home from the store once a week. You will notice that the tow RATING for a truck with economy gearing is for less weight than one with tow gears. While it IS possible to tow with higher gears it is FAR from pleasant to be traveling up a minor grade like 06% as found on Interstate highways at 30 MPH while others are passing you at 70. Not pleasant and downright dangerous. Good luck / skip


2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR -
2004 F-150 HD (Traded after 80,000 towing miles)
2007 Rockwood 8314SS 34' travel trailer

US Govt survey shows three out of four people make up 75% of the total population


enginemasterguru

near Bear Lake

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Posted: 02/17/11 08:37am Link  |  Print  |  Notify Moderator

That's just silly.
Once I used a 165-HP ( at 4000 rpm ) 4.3, with 3.73:1 axle, to tow a 7500 pound load up a 6% grade, and I made it without struggling. I was doing 30 mph at 4400 rpm in first gear, but it didn't hurt anything. I didn't even turn the radio up.
A 5.9 or a hemi will tow 8000 pounds with a 3.55:1 axle. No worries.
If you don't like RPM, then switch to diesel.

mich800

Pontiac, MI

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Posted: 02/17/11 08:49am Link  |  Print  |  Notify Moderator

big dave wrote:

mich800 wrote:

I do not think the Hemi was offered until the early 2000's. But I agree with the rest. Gearing is a compromise. The only time I ever got into OD with my Ford 5.4 was maybe going downhill. But I did not have a problem wringing it out on the hills if that is what it takes.

Chrysler built a few hemi engines during World War 2 but none ever went into production. One developed over 3,000 h.p in a V16 configuration. The first hemi mass produced for an automobile was Introduced in the fall of 1950 as a 1951 model, the Fire Power 331 V-8 was offered as on option in the Saratoga (except for the coupe models), while it was standard in the New Yorker and Imperial.


Read more: http://wiki.answers.com/Q/When_was_the_hemi_introduced#ixzz1EEMk4JCb


I meant after its hiatus. I am aware there was a hemi prior to 20xx.

ib516

Way up north eh

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Posted: 02/17/11 09:23am Link  |  Print  |  Notify Moderator

Well, not a Hemi, but I can tell you from experience that a 360 cu in gasser (245hp) did not have enough power (FOR MY TASTES) towing 8500 - 9000# in the mountains, even with 4.10 gears. ~30 mph up the mountain grades at 4000 RPM, in 2nd gear, watching traffic pile up behind me wasn't my idea of fun. That was a 2001 Dodge 2500 with the 360 gasser engine.

Heck, that truck had to downshift out of OD to climb those grades when running WITHOUT the trailer. I then later drove my 2002 2500 Dodge/Cummins (with a 3.55 axle ratio) from home all through the Canadian Rockies to go to a wedding - didn't take the RV. The truck never downshifted once climbing the grades. Towing the RV, it would downshift on some hills, but it mostly stayed in OD, and the turbo just spooled up when climbing.


Prev: 2010 Cougar 322QBS (junk)
02 Dodge 2500 4x4 5.9L CTD 3.55
07 Dodge 3500 4x4 SRW Mega 5.9L CTD 3.73
14 Ram 2500 4x4 Crew 6.4L Hemi 4.10
06 Chevy 1500 4x4 E-Cab 3.73 5.3L
All above are sold
Current: 07 Dodge 1500 5.7L Hemi 3.55 / 2010 Jayco 17z


overw8chevy

florida

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Posted: 02/17/11 09:25am Link  |  Print  |  Notify Moderator

I'm humoring myself now trying to figure out if the OP was a question or a observation

mkirsch

Rochester, NY

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Posted: 02/17/11 10:37am Link  |  Print  |  Notify Moderator

enginemasterguru wrote:

That's just silly.
Once I used a 165-HP ( at 4000 rpm ) 4.3, with 3.73:1 axle, to tow a 7500 pound load up a 6% grade, and I made it without struggling. I was doing 30 mph at 4400 rpm in first gear, but it didn't hurt anything. I didn't even turn the radio up.
A 5.9 or a hemi will tow 8000 pounds with a 3.55:1 axle. No worries.
If you don't like RPM, then switch to diesel.


Some would say 30MPH in 1st gear at 4400RPM is the dictionary definition of "struggling," especially if you're on an interstate and everyone else is whizzing by you at 55-75MPH.

Would you be able to tolerate a 250-mile trip at 30MPH and 4400RPMs? With the wife and kids? On a regular basis?

Sure you can do it to run the Bobcat across town to the next job, or haul a load of cinder blocks home from Lowes, but we're not talking about short and/or one-time things.

When you spend that much money on a truck and trailer to go camping, you tend to want to do it more than once.

BenK

SF BayArea

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Joined: 04/18/2002

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Posted: 02/17/11 10:43am Link  |  Print  |  Notify Moderator

One size does NOT fit all...

Also, folks range from not able to tell if there was an earthquake even if the
epicenter was between their legs...to those who can feel it hundreds
of miles away

Some love the sound of an ICE turning 5,000 RPMs for hours on end. I'm not one
of them on any of my trucks, but do love that sound on a V12 or my in-line six
2 seater...but it's a sports car, not a TV. Why I have a big block
for my main TV. My 'half ton' (heavy half of it's time) has a 'built'
small block (5.7L, ported, cam, stainless valves, 3 angle grind, flow
matched, CC'd, polished chamber and runners, Edelbrock High Raise Performer
intake, Edelbrock Performer 4 barrel, etc) and a 'built' auto tranny
with a shift kit, 'built' 12 bolt, etc it's okay and like the sound
at around 3.5K RPMs (no tach, so guessing)...but it's towing days are
over and both my daughters used to go out and beat up pony cars on the
local boulevard.

Some think nothing of driving at 80% throttle for hours on end and 100% throttle
for an hour or so climbing a mountain. NOT me, as I keep mine for a
looooooong time and like NOT to have to rebuild that often.

Many think they know more than the OEMs, so advise others who come here looking
for help, that it's okay to tow heavy while in OD and turn off the tow/haul function

It all depends... [emoticon]


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

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