V6 vs V8 Tow Rating...what changes?

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Elite130
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V6 vs V8 Tow Rating...what changes?

Postby Elite130 » Fri Apr 08, 2011 1:57 pm

Hey all, I have a question regarding the towing abilities of the V6 vs V8...

What is the difference between the V8 and the V6 other than the engine? How does the V8 get 7,000lb towing capacity over the V6's 6,000lb? Are the brakes different, is the suspension different, what about the hitch?

I'm thinking if there is nothing different between the V6 and V8 Pathfinders aside from engine, can we assume the V6 can handle the same loads as the V8's, structurally and braking power-wise? The V6 would just be short on power.


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yeziam
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Postby yeziam » Fri Apr 08, 2011 5:53 pm

I'm assuming the hitch is the same as the tow capacity sticker on the hitch of my v6 has tow ratings for the v8 and v6. Don't quote me on it, but I'm fairly certain the suspension and brakes are also the same. I have towed over capacity and had no issues stopping, but it would have been nice to have the v8 torque to get everything moving.

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Postby skinny2 » Fri Apr 08, 2011 6:32 pm

You do have to wonder because in most cases, the engine is the least important driver of towing capacity. In many cases, you'll see the smaller engine actually have a higher capacity simply because it's lighter (particularly in diesel trucks vs gas).

The rear brakes are disc on the V8. That's also not usually the limiting factor because the specs normally call for trailer brakes above 1,500# or so regardless of overall capacity.

The rear-ends and axles are different between the two...although it appears to be pretty minor.

Suspensions are identical.

OEM Tires have similar load ratings.

I'm stumped. It has to be in the rear-end I guess.

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Postby volvite » Fri Apr 08, 2011 7:01 pm

The overall structrue of the pathfinder is not changed for a V6 to V8. Most parts are the same. However there are the differences on power to weight ratio. Look at any vehicle and it's the same way. Your bigger engine is going to give you the better of the two in towing capacity. Less work involved in towing higher amouts of weight. Also that bigger engine is going to give your vehicle an overall heavier weight to help compensate for the bigger load. This might help:

Maximum Trailer Weight=
The absolute maximum that the trailer should weigh is the difference between GVW and GCWR. If the manufacturer-specified Maximum Trailer Weight is lower, then it takes precedence.
GVW=Gross Vehicle Weight
GCWR=Gross Combination Weight Rating is the maximum number that the tow vehicle GVW plus the trailer GVW should never exceed

Hope that helps.

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Postby skinny2 » Sat Apr 09, 2011 8:49 am

volvite wrote:The overall structrue of the pathfinder is not changed for a V6 to V8. Most parts are the same. However there are the differences on power to weight ratio. Look at any vehicle and it's the same way. Your bigger engine is going to give you the better of the two in towing capacity. Less work involved in towing higher amouts of weight. Also that bigger engine is going to give your vehicle an overall heavier weight to help compensate for the bigger load. This might help:

Maximum Trailer Weight=
The absolute maximum that the trailer should weigh is the difference between GVW and GCWR. If the manufacturer-specified Maximum Trailer Weight is lower, then it takes precedence.
GVW=Gross Vehicle Weight
GCWR=Gross Combination Weight Rating is the maximum number that the tow vehicle GVW plus the trailer GVW should never exceed

Hope that helps.
That's all true (although power/weight ratio isn't usually a factor in setting a tow rating..it's usually axles, suspension, chassis, etc). You could pull these loads with a lot less power than either V6 or V8....just not as quickly. Recall many far less powerful vehicles in the past were used for towing loads like this.

That being said, according to my manual:

V8 has approx. 200# additional GVWR and 100# of that is chewed up by the heavier V8 engine. So overall, the V8 has 100# more payload capacity than the V6.

V8 also has approx. 1,400# additional GCVWR.

I'm sticking with my theory that the axles/rear-end is a rated for the extra weight because that's about the only mechanical differences that are really factored in payload.

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hfrez
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Postby hfrez » Fri Nov 04, 2011 5:53 am

I think you are all forgetting the importance of the transmission in towing. I cannot believe or assume that the V8 has the same tranny as the V6. Gearing becomes a big issue also and the amount of them. I know that the V8 tranny also has 5 gears but I must believe that it is a bigger transmission and holds more fluids and may also have a bigger radiator up front.

One thing I already noticed is that rear drive axle ratio for the 2011 V6 is 3.13 and for the 2011 V8 it is 2.93. This may not seem like much but it makes a big difference. The smaller the number the better for towing the worse the Mpg's.

Also I noticed that the V8 only comes in 4W Drive which makes a difference in towing as well.

Trucks are the same way. They mostly have the same frame and body setup but the engine in conjunction with the transmission and rear end is what gives an F150 different towing capabilities. It is not just all about weight either but the tow vehicle must have a minimum weight for it to tow a certain capacity.

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Postby disallow » Fri Nov 04, 2011 7:42 am

hfrez wrote:I think you are all forgetting the importance of the transmission in towing. I cannot believe or assume that the V8 has the same tranny as the V6. Gearing becomes a big issue also and the amount of them. I do not know how many gears are in the V8 tranny but I must believe that it is a bigger transmission and holds more fluids and may also have a bigger radiator up front.

One thing I already noticed is that rear drive axle ratio for the 2011 V6 is 3.13 and for the 2011 V8 it is 2.93. This may not seem like much but it makes a big difference. The smaller the number the better for towing the worse the Mpg's.

Trucks are the same way. They mostly have the same frame and body setup but the engine in conjunction with the transmission and rear end is what gives an F150 different towing capabilities. It is not just all about weight either but the tow vehicle must have a minimum weight for it to tow a certain capacity.
Several assumptions you are making are not correct here:

1. The transmission is the same, in fact the RE505A is the same for Pathy, Xterra, Frontier, and Titan. The torque converters will probably be different dependent on engine torque available.

2. Gearing - 2.93 vs 3.13 means the V8 has taller gearing and will run at lower RPMs vs the V6 at any given speed. This is because the V8 has more torque available and can support this. It would in fact make the towing situation more difficult. For instance, on most 3/4 and 1 ton trucks, guys will often go for 3.73 vs 3.42 gearing to ensure they can tow. Fuel economy goes down when not towing as the engine is running at higher RPM.

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hfrez
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Postby hfrez » Fri Nov 04, 2011 7:58 am

I guess the point I'm trying to make is that there are differences between the V6 & V8 other than just engines that affect the towing. You would have to agree with that!

Just look at the specs of the two transmissions. They may have the same factory code but they are geared different and this will affect towing.

Transmission V6
Drivetrain Rear Wheel Drive
Trans Type 5
Trans Description Cont. Automatic
First Gear Ratio (:1) 3.84
Second Gear Ratio (:1) 2.35
Third Gear Ratio (:1) 1.52
Fourth Gear Ratio (:1) 1.00
Fifth Gear Ratio (:1) 0.83
Reverse Ratio (:1) 2.76
Final Drive Axle Ratio (:1) 3.13

Transmission V8
Drivetrain Four Wheel Drive
Trans Type 5
Trans Description Cont. Automatic w/manual mode
First Gear Ratio (:1) 3.82
Second Gear Ratio (:1) 2.36
Third Gear Ratio (:1) 1.52
Fourth Gear Ratio (:1) 1.00
Fifth Gear Ratio (:1) 0.83
Reverse Ratio (:1) 2.61
Final Drive Axle Ratio (:1) 2.93

In 1st gear, the engine makes 3.82 revolutions for every revolution of the transmission’s output. In 4th gear, the gear ratio of 1:1 means that the engine and the transmission’s output are moving at the same speed. 5th and 6th gears are known as overdrive gears, in which the output of the transmission is revolving faster than the engine.
Last edited by hfrez on Fri Nov 04, 2011 8:28 am, edited 1 time in total.

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hfrez
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Postby hfrez » Fri Nov 04, 2011 8:21 am

The gear ratio in a vehicle’s differential. The ratio expresses the number of turns required by the pinion (which is attached to the output shaft of the transmission) to turn the drive axle one revolution, i.e. 2.73:1 means the pinion must turn 2.73 times to turn the drive axle once. A higher number means a lower (or shorter) gear. Short gearing gives quicker acceleration, but because the engine must turn faster, gas mileage and top speed are lower. Tall gears give better acceleration and higher top speed, at the expense of acceleration.

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Postby skinny2 » Fri Nov 04, 2011 9:03 am

I'm still going with the rear-end being the factor. Outside of the engine, it's the only mechanical part that's different. If power was the leading indicator of the tow rating, why wouldn't the V8 have a higher GVWR? Something mechanical in drivetrain is limiting the tow rating and I really don't think it's performance.

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Postby found » Sat Nov 05, 2011 8:13 am

Your main factors are power to weight, axle ratio, and brakes.

the v8 and v6 have the same trans (slightly diff ratios), same drive shaft, and same rear diff assembly (slightly diff ratios). which leads me to believe the additional 50 hp 100lb/ft torque are the difference. In all the specs i have read the brakes are the same between the two as well. I think I also saw a post somewhere saying that the v8 rear springs are stiffer then v6 springs, but who knows if that is true.

anyway, after towing 6k lbs with my v6 pathy i can see its limitation was hp/tq related. . .particularly in the mountains. brakes were just fine, fantastic actually and nothing got too warm it was just struggling to maintain 65mph

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Postby found » Sat Nov 05, 2011 8:21 am

hfrez wrote:I guess the point I'm trying to make is that there are differences between the V6 & V8 other than just engines that affect the towing. You would have to agree with that!

Just look at the specs of the two transmissions. They may have the same factory code but they are geared different and this will affect towing.

Transmission V6
Drivetrain Rear Wheel Drive
Trans Type 5
Trans Description Cont. Automatic
First Gear Ratio (:1) 3.84
Second Gear Ratio (:1) 2.35
Third Gear Ratio (:1) 1.52
Fourth Gear Ratio (:1) 1.00
Fifth Gear Ratio (:1) 0.83
Reverse Ratio (:1) 2.76
Final Drive Axle Ratio (:1) 3.13

Transmission V8
Drivetrain Four Wheel Drive
Trans Type 5
Trans Description Cont. Automatic w/manual mode
First Gear Ratio (:1) 3.82
Second Gear Ratio (:1) 2.36
Third Gear Ratio (:1) 1.52
Fourth Gear Ratio (:1) 1.00
Fifth Gear Ratio (:1) 0.83
Reverse Ratio (:1) 2.61
Final Drive Axle Ratio (:1) 2.93

In 1st gear, the engine makes 3.82 revolutions for every revolution of the transmission’s output. In 4th gear, the gear ratio of 1:1 means that the engine and the transmission’s output are moving at the same speed. 5th and 6th gears are known as overdrive gears, in which the output of the transmission is revolving faster than the engine.
Actually the numerically lower ratio will negativly affect the v8 pathy not positivly affect. since it will be more difficult for the engine to turn the wheels (better for fuel economy) which is why i think the v8 only gains you 1k lbs towing capacity of the v6. Same with the rear diff, numerically higher gear rations make it easier for the engine to spin the wheels etc.

18 wheelers for example, the rear diff is around a 5.90:1 and are typically set up behind atleast a 10 speed trans. which has a starting ratio of 15:1 ish all the way to 1:1

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Postby disallow » Sat Nov 05, 2011 10:00 pm

found wrote:Your main factors are power to weight, axle ratio, and brakes.

the v8 and v6 have the same trans (slightly diff ratios), same drive shaft, and same rear diff assembly (slightly diff ratios). which leads me to believe the additional 50 hp 100lb/ft torque are the difference. In all the specs i have read the brakes are the same between the two as well. I think I also saw a post somewhere saying that the v8 rear springs are stiffer then v6 springs, but who knows if that is true.

anyway, after towing 6k lbs with my v6 pathy i can see its limitation was hp/tq related. . .particularly in the mountains. brakes were just fine, fantastic actually and nothing got too warm it was just struggling to maintain 65mph
+1, totally agree.

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disallow
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Postby disallow » Sat Nov 05, 2011 10:01 pm

found wrote:
hfrez wrote:I guess the point I'm trying to make is that there are differences between the V6 & V8 other than just engines that affect the towing. You would have to agree with that!

Just look at the specs of the two transmissions. They may have the same factory code but they are geared different and this will affect towing.

Transmission V6
Drivetrain Rear Wheel Drive
Trans Type 5
Trans Description Cont. Automatic
First Gear Ratio (:1) 3.84
Second Gear Ratio (:1) 2.35
Third Gear Ratio (:1) 1.52
Fourth Gear Ratio (:1) 1.00
Fifth Gear Ratio (:1) 0.83
Reverse Ratio (:1) 2.76
Final Drive Axle Ratio (:1) 3.13

Transmission V8
Drivetrain Four Wheel Drive
Trans Type 5
Trans Description Cont. Automatic w/manual mode
First Gear Ratio (:1) 3.82
Second Gear Ratio (:1) 2.36
Third Gear Ratio (:1) 1.52
Fourth Gear Ratio (:1) 1.00
Fifth Gear Ratio (:1) 0.83
Reverse Ratio (:1) 2.61
Final Drive Axle Ratio (:1) 2.93

In 1st gear, the engine makes 3.82 revolutions for every revolution of the transmission’s output. In 4th gear, the gear ratio of 1:1 means that the engine and the transmission’s output are moving at the same speed. 5th and 6th gears are known as overdrive gears, in which the output of the transmission is revolving faster than the engine.
Actually the numerically lower ratio will negativly affect the v8 pathy not positivly affect. since it will be more difficult for the engine to turn the wheels (better for fuel economy) which is why i think the v8 only gains you 1k lbs towing capacity of the v6. Same with the rear diff, numerically higher gear rations make it easier for the engine to spin the wheels etc.

18 wheelers for example, the rear diff is around a 5.90:1 and are typically set up behind atleast a 10 speed trans. which has a starting ratio of 15:1 ish all the way to 1:1
This is what I (unsuccessfully) was trying to get across.

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hfrez
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Postby hfrez » Sun Nov 06, 2011 6:38 am

I guess in a sense we have been talking about the same thing. The bottom line is the setup between the V8's engine, transmission and rear end are its limiting factors.


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