What it Really Weighs

[cochise]

I think that too many people put emphasis on horse power alone, when in reality there are at least two (2) other factors of great importance: The transmission gearing and the rear end gearing. If the gearing is right a lesser HP engine may be able to do the work. I tow with a Silverado 4.3L V6 engine and a 3.42:1 rear end, which allows me to tow 5000 Lb. Had I had a 3.08:1 rear end I could only tow 4500 Lb. For a 4.8L V8 with a 3.42:1 rear end it can tow 6400 Lb but a 3.73:1 rear can tow 7400 Lb. So I think the gear ratio of the rear end has a LOT to do with how much you can tow.

[Mr. Adventure]

Originally Posted by cochise

I think that too many people put emphasis on horse power alone, when in reality there are at least two (2) other factors of great importance: The transmission gearing and the rear end gearing. If the gearing is right a lesser HP engine may be able to do the work. I tow with a Silverado 4.3L V6 engine and a 3.42:1 rear end, which allows me to tow 5000 Lb. Had I had a 3.08:1 rear end I could only tow 4500 Lb. For a 4.8L V8 with a 3.42:1 rear end it can tow 6400 Lb but a 3.73:1 rear can tow 7400 Lb. So I think the gear ratio of the rear end has a LOT to do with how much you can tow.

The rear end ratio is likely to be more about durability than anything else because lower gears mean lower transmission stresses as well as better engine leverage (and probably lower gas mileage too). By making the rear end ratio a user selectable option, manufacturers can extend the operational range of the product line a bit, which is also great for marketing reasons.

But it doesn't make any difference where the manufacturer chooses to gear things as long as they do a good job at it. In other words, we don't particularly care whether they set the ratios at the transmission, the rear end, or the size of the drive wheels as long as the end result is appropriate.

[T and C]

It's possible that I would own a different tow vehicle if I towed over the pass and through the Eisenhower tunnel every week, but I'm not worried about visiting there again someday.

Mr. A,

Your mention of the Eisenhower Tunnel touched off a memory that illustrates the point you are making. Many years ago I needed an economical car to make my daily 52 round trip commute to work in. It had to be a used car, so I ended up with a 1983 AMC/Renault Alliance. It had a 1.4 liter 4 cylinder motor that put out a roaring 54 horsepower. Coupled with a 5 speed transmission it got great gas mileage. As I recall, you could get into the low 40's in steady highway cruising.

Anyhow, I needed to get to Estes Park, CO for a conference. So the wife and I decided to drive the Alliance. When we got to the Rockies, coming from the west, we expected to creep up the mountian to the tunnel. I had made the trip previously in large American V-8's that had turned into gutless wonders above about 8000 feet. Seems to me that that pass is about 11,000 feet.

The Alliance cruised up the mountain at 50mph with no apparent strain. I used 3rd gear all the way and passed just about everything! A friend's Cadillac deisel could not make it and had to be towed.

So, the combination of weight, power, and gearing are sort of an equation that figures out to: you make it, or, you don't. You seem to have the situation well in hand.

Tom

[Wavery]

Originally Posted by Mr. Adventure

The rear end ratio is likely to be more about durability than anything else because lower gears mean lower transmission stresses as well as better engine leverage (and probably lower gas mileage too). By making the rear end ratio a user selectable option, manufacturers can extend the operational range of the product line a bit, which is also great for marketing reasons.

But it doesn't make any difference where the manufacturer chooses to gear things as long as they do a good job at it. In other words, we don't particularly care whether they set the ratios at the transmission, the rear end, or the size of the drive wheels as long as the end result is appropriate.

That's correct. My TV is a case in point.

I almost did not buy this truck because it has a 3:23 final drive ratio with the 4.8L V8. I purchased the truck with every intention of installing a 3:73 ring & pinion.

However, after towing TM for several thousand miles and a couple trips over the Rockies with elevations to 11K', I have been pleasantly surprised with this combination.

When climbing steep grades, I just slip it into 2nd and set the cruise control @ 52MPH. The engine turns a happy 3300RPm which is close to it's optimum torque range and far from over-revving. There is no strain on the engine, it runs normal temps and the trans runs normal temps. I happily pass about any RV on the road and have the ability to accelerate to 65MPH (in 2nd) if need be (for passing) without red-lining the engine.

If I switched to the 3.73 gears, I don't think that I would be as happy with the over-all performance and MPG.

[scrubjaysnest]

Our Dodge has about a 3:42, for flat country I disable one of the over drives, tow/haul and never see anything above 2500 rpm. This lets me set the cruise at 62 and forget it. Haven't gotten the TM in major terrain yet but will most like have to disable all over drives, OD off. This worked great with the pup last year but then it was about 700 to 800 pounds lighter. Our truck likes 62 to 65 mph for best fuel mileage and doesn't care if your towing or not. The DW's Cherokee with the same 4.8L v8 likes 67 mph for interstate travel when not towing. Both vehicles get better mileage when using regular gas without ethanol. But then we must support our farmers.

Originally Posted by harveyrv

When climbing steep grades, I just slip it into 2nd and set the cruise control @ 52MPH. The engine turns a happy 3300RPm which is close to it's optimum torque range and far from over-revving. There is no strain on the engine, it runs normal temps and the trans runs normal temps. I happily pass about any RV on the road and have the ability to accelerate to 65MPH (in 2nd) if need be (for passing) without red-lining the engine.

Wayne has hit the magic word here....TORQUE..
When lowering your gear ratio, the resulting output HP will not change (it may actually go down slightly), only the output torque goes up.
Torque is the key factor that starts the momentum and allows acceleration (under load or climbing hills).
Horsepower is what keeps the momentum going once it's moving.

As everyone has realized, finding the right "sweet spot" within the almost infinite HP/TORQUE/RATIO combinations is the trick. Most manufacturers offer combination that could be called "normal", "heavy duty", and "extra HD" (F150, F250, F350, etc) that have this pretty well thought out already.

[Mr. Adventure]

Originally Posted by ED-n-KEL

...As everyone has realized, finding the right "sweet spot" within the almost infinite HP/TORQUE/RATIO combinations is the trick. Most manufacturers offer combination that could be called "normal", "heavy duty", and "extra HD" (F150, F250, F350, etc) that have this pretty well thought out already...

If your manufacturer thought it out right in the first place, you wouldn't have to be messing around with rear end ratios. Honestly guys, this board can't talk about blueberry muffins without talking about pickup trucks.

Here's a great stock torque curve for you:
http://www.knfilters.com/dynocharts/69-8611_dyno.pdf

[Wavery]

Originally Posted by Mr. Adventure

If your manufacturer thought it out right in the first place, you wouldn't have to be messing around with rear end ratios. Honestly guys, this board can't talk about blueberry muffins without talking about pickup trucks.

Here's a great stock torque curve for you:
http://www.knfilters.com/dynocharts/69-8611_dyno.pdf

No blueberry muffins in our pickup.........I'm allergic to wheat....

follow this link harvey, and then you'll be able to talk about pickup trucks:

http://www.wheat-free.org/blueberry-muffin.html

Originally Posted by Mr. Adventure

If your manufacturer thought it out right in the first place, you wouldn't have to be messing around with rear end ratios. Honestly guys, this board can't talk about blueberry muffins without talking about pickup trucks.

Many people buy used vehicles, which then become TVs...but may not have had the factory tow package....thus simply changing the rear end can reap higher TCs.
For example my Astro was sold with 3 different ratios...3.23, 3.42, and 3.73.
I bought it used with a 3.23 (4500 lb tc) before ever thinking of towing.
The 3.73 came with the ftp and reaps a 5500 lb tc, thus changing to a 3.73 would be beneficial.
Many people out there are in the same boat, towing with used TVs, bought without the optimum ratio for towing. The ratios were well thought out by the factory, and if buying a new TV, you can choose the best for your application, but when you buy used, you get what you get.

The reference to PU's was only done for clearer understanding by all, since PU's are way more popular and used by many for towing. (Oops....another post about PUs! Sorry Mr A.)