04.5 with 4.10's <vs> 07.5 with 3.73's towing 15,500lbs

[p-Bar]

AH64ID, Do you actually tow constant @ 2200rpm?



Just asking, because unless I'm passing I rarely ever hit those revs. In fact anything over 1800/2000rpm my mileage goes to heck, and I do not need to be in that range to tow comfortably. I understand my truck(48re/3. 73, 35" tires) is not configured to the OP's question, but I tow all day long at 70mph/1800rpm, usually only slow down for traffic, corners and nighttime.



2200rpm maybe the rpm that maximum torque is available, glad I don't need it. With exception of my injectors, my fueling is turned back to stock while towing, or Smarty sw#1, because I lose my tire calibration when I return to stock.



I'm thinking you were just using 2200rpm for a mph correlation in each gear to compare... Jess

1800 is the sweet spot for mileage

 

[AH64ID]

AH64ID, Do you actually tow constant @ 2200rpm?



Just asking, because unless I'm passing I rarely ever hit those revs. In fact anything over 1800/2000rpm my mileage goes to heck, and I do not need to be in that range to tow comfortably. I understand my truck(48re/3. 73, 35" tires) is not configured to the OP's question, but I tow all day long at 70mph/1800rpm, usually only slow down for traffic, corners and nighttime.



2200rpm maybe the rpm that maximum torque is available, glad I don't need it. With exception of my injectors, my fueling is turned back to stock while towing, or Smarty sw#1, because I lose my tire calibration when I return to stock.



I'm thinking you were just using 2200rpm for a mph correlation in each gear to compare... Jess

2000-2200 is commonly refereed to as the "sweet spot" for the HPCR motors. A look at a stock dyno shows why, 2000 rpms has a major power increase and for me I get more power and lower EGT's that 1900. I am not saying I can't pull at 1800-1900 but 2200 is much better. I generally pull all my hills in 5th at 2200, or 6th at 2000 if the road permits.

 

[jray]

AH64ID Said:

2000-2200 is commonly refereed to as the "sweet spot" for the HPCR motors. A look at a stock dyno shows why, 2000 rpms has a major power increase and for me I get more power and lower EGT's that 1900. I am not saying I can't pull at 1800-1900 but 2200 is much better. I generally pull all my hills in 5th at 2200, or 6th at 2000 if the road permits.

I had never heard of this as being the sweet spot before. I normally tow at 1800 rpm and find that the lower rpm's actually save fuel. As long as the egt's remain in check and you are able to maintain a desired speed, why would you want higher rpm's?

 

[AH64ID]

As long as the egt's remain in check and you are able to maintain a desired speed, why would you want higher rpm's?

Coolant and oil circulation are one thing for sure. With a real oil psi gauge you can see how much the oil heats up on long grades with the EGT's and coolant temps in check. It's just an easier pull.



Mechanical advantage is another reason to drop a gear an go to 5th at slightly higher rpms. In addition to the slower speed the slightly greater tq multiplication will reduce power requirements, thus reducing fuel consumption.



I do plenty of towing in 6th at 1800-1900 rpms, but prefer to pull big grades at 2000+ even if I have the power at lower rpms. Admittedly I do pull more grades in 6th with the new turbo and added hp just because I can.

 

[HBarlow]

jray,

I prefer lower rpm also. I usually prefer to tow at 1800 to 2100 rpm depending on road and speed limit.

 

[AH64ID]

jray,



I prefer lower rpm also. I usually prefer to tow at 1800 to 2100 rpm depending on road and speed limit.

Is that on flats or thru the mountains?

 

[HBarlow]

Is that on flats or thru the mountains?

Your point is good.

I live in mostly flat country so tend to cruise along at 62 mph in Tow/Haul with sixth gear locked out.

In the hills I would tend to use around 2200 rpm or more instead.

 

[AH64ID]

Your point is good.

I live in mostly flat country so tend to cruise along at 62 mph in Tow/Haul with sixth gear locked out.

In the hills I would tend to use around 2200 rpm or more instead.

Which is about what I do. 60-65 on the flats which puts me at 1800-1950, and either speed up to 67-70 for hills with lighter loads (2000-2100) or drop to 5th and 55 (2250) for heavier loads.

I try to drive the speed limit, occasionally up to 70 max but normally 65 max, when towing.

If I could do 62 with the . 77 5th gear of the Aisin when towing I would be super happy!... I really want a 7 speed manual.

 

[AClayton]

I know you guys have the common rail trucks, but the 2nd gens do best around the 1800 to 2000 mark. I did find myself locking out the OD the other day when I was pulling my RV through the hills in PA. I was on my way to Reading,PA last weekend when temps outside hit over a 105* plus high humidity. Truck did not like this at all and this is why we all have gauges! A quick downshift to 3rd with convertor locked and a reduced speed to 55mph lowered the temps to a more comfortable reading. I was spinning around 2200rpms which is loud in our trucks but it was a necessary evil to keep coolant flow high. That was the hottest day I have ever towed and was pleased with how my truck handled the heat.

 

[Road Dog]

Around here it's all about mountain driving and speed limits of 90k/hr (55mph). With 3. 55 gears I lock out O/D and spend most of my time in 2nd & 3rd and keep my rpm over 2,000. It keeps my exhaust temps below 1,200F. The HY35 turbo doesn't help.

 

[jeepit]

With 3. 55s and empty I'll cruise at 70 which puts me 2100-2200. Motor sounds cool and runs great.

With a load of 8,000lbs I'll run that in the flats and downshift to 5th for power if needed for hills and such.

 

[AH64ID]

With 3. 55s and empty I'll cruise at 70 which puts me 2100-2200. Motor sounds cool and runs great.

With a load of 8,000lbs I'll run that in the flats and downshift to 5th for power if needed for hills and such.

What tires are you running? That seem's like a lot of RPMs for 3. 55's and a NV-5600 . 73 OD, tires would have to be much smaller than anything that came on a 4wd in 02.

 

[Barry]

Another factor for towing high profile loads is wind resistance and drag. When you tow a HP trailer over 62 mph, your horse power demand and direct operating costs go straight up.

We tow 60 to 62 mph and run 68 empty. Fuel costs too much. And when you are on SS, whats time?

 

[Okie-Go]

I know this sounds terrible but at 100 miles round trip I would get the onne I wanted. That is not much towing at all.

Okie

 

[Mikey-KE7LBB]

3. 73's are never suitable for towing with A6's ? Can you expand on the reasons, or point me to a link with the info ?



Downshifting into 5th is good advice and would be what I'd be doing to keep it in the sweet spot range.

The lower 4. 10 rear end will run much cooler than a higher ratio towing the same load due to reduced pressure between the ring & pinion... The same applies to the transmission and is the reason that the owner's manual says to avoid towing in OD.



There is also the added cooling from the engine fan being able to draw more air through the rad. Also the oil and coolant temps will run lower due to the added mechanical advantage and reduced engine load.



Any pickup that tows heavy more than 50% of the time would surely benefit from the 4. 10's...



The 4500/5500's are built to tow heavy all the time and are frequently outfitted with utility beds, cranes, buckets (power company), roll backs to haul off the busted 6. oh no! Furds :-laf AND sometimes the trailer that broke the turd (oops! I meant Furd) to begin with , welding equipment, extra fuel tanks and thousands of pounds of tools, etc... That's why they don't offer the same gear ratios as the pickup trucks do .

So tell me, why would anyone want 3. 73 or 3. 42 gears for towing?

I have the 3. 73's in my '09 and love the way it pulls my 39' toyhauller maybe once or twice a year to go hunting or just to get away for a few days. But, If I were a 'full-timer' or towed to earn a living, I would have to agree with Harvey 100%



Truth be told... I wanted the 4. 10's, but I got one heck of a deal on this truck that only had 3 miles on it when I drove it off the lot



I do tow in 6th sometimes, but the hills and wind have me in 5th (direct) most of the time to preserve the trans, clutch, and that POS excuse for a flywheel :-laf

 

[jeepit]

What tires are you running? That seem's like a lot of RPMs for 3. 55's and a NV-5600 . 73 OD, tires would have to be much smaller than anything that came on a 4wd in 02.

Correction 1900-2000.