Tow Ratings?
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Tow Ratings?
Why are light duty vehicles like 1/2-2 ton trucks rated so funny?
How does engine, trans, and rear axle ratio affect stability and braking?
If you order a HD truck with the same frame, springs, axles, brakes you get the same GVWR / GCWR whether you get a 250 hp / 950 torq engine or a 600 hp / 2050 torq engine and gear ratios play absolutely no role in ratings.
If a typical class 8 truck can be rated 90,000 lb with only 470 hp / 1650 torq I fail to see why a 145 hp / 265 torq 4.9L I6 F150 would need it's GCWR reduced from 12,000 lb to 10,000 lb with the only change being the loss of the 5.8L engine (Same trans and rear axles).
After all based on torque to weight a 265 torq 4.9L should be capable of a GCWR of 14,500 lb no problem.
So if a 5.8L is safe at 12,000 lb GCWR why wouldn't a 4.9L be?
Is this just a marketing decision based on the performance expectations of consumers with no real engineering basis?
How does engine, trans, and rear axle ratio affect stability and braking?
If you order a HD truck with the same frame, springs, axles, brakes you get the same GVWR / GCWR whether you get a 250 hp / 950 torq engine or a 600 hp / 2050 torq engine and gear ratios play absolutely no role in ratings.
If a typical class 8 truck can be rated 90,000 lb with only 470 hp / 1650 torq I fail to see why a 145 hp / 265 torq 4.9L I6 F150 would need it's GCWR reduced from 12,000 lb to 10,000 lb with the only change being the loss of the 5.8L engine (Same trans and rear axles).
After all based on torque to weight a 265 torq 4.9L should be capable of a GCWR of 14,500 lb no problem.
So if a 5.8L is safe at 12,000 lb GCWR why wouldn't a 4.9L be?
Is this just a marketing decision based on the performance expectations of consumers with no real engineering basis?
Elder User
Joined: Jun 2003
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From: Castle Rock, Colorado
Tow Ratings?
A 5.8L won't have to work as hard compared to a I-6. Not that a I-6 couldn't do it...but you'll be at higher RPM and stress on a I-6 than the 5.8L. I don't know specifics, but that's how I rationalize it. It's the same compalint that I have on my tranny. I have a 5spd, if I would hve had the auto, my tow capacity goes up over 1k lbs.
Postmaster
Joined: Mar 2001
Posts: 4,968
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From: So Cal
Tow Ratings?
Your question is a bit confusing so I'll go with the usual spiel, which can be confusing since I tend to ramble sicne it is a complex subject, sorry.
The tow rating is based upon many factors which have been evaluated by the factory to provide "Satisfactory" service life and minimal warranty issues.
You can tow almost any weight with any vehicle as long as you have traction and don't physically destory the tow vehicle just hooking up. I once pushed a 30foot motor home uphill with my 74 Datsun truck with 1800 engine and 4 speed, I was young and stupid.
What the factory is figuring is that you want to be able to tow for longer than a couple thousand miles without having to rebuild your truck every few thousand.
The engine, tranny and axle ratio are part of the equation but if the frame, axles, or hitch cannot hold the load then you have a reliability and safety issue.
If the brakes are too small you got a liability issue. And way too exciting for me to drive.
If the cooling system can't handle the heat you got a problem.
Bearings in the axle have a big effect on load carrying capacity.
Shocks and springs are different for towing. Tires and wheels are higher rated for towing. Don't haul a 10,000# trailer if your truck has sporty wheels and nice car type tires with low load ratings.
The electrical system may also be different.
I probably missed a few things but in general just because you have a big engine does not mean you can tow for squat.
2 examples. The Old Chevy 454 sport truck had essentailly a truck engine right? Pretty similar to our workhorse 460s as far as tow power. But the 454 truck had a relatively low tow rating, I think something ludicrous like 2,000# or at best 5,000#. The reason the rating was so low was the brakes, axle bearings, springs and shocks, tires and wheels and maybe a couple other things. The truck was designed for fun and sportyness not towing.
An easier example. I have a 96 Impala SS. The standard base model would be a Caprice. The SS tow rating is only 2,000#, the Caprice is something like 5,000#. The engine and tranny and diff is essentially identical. The SS Frame is actually a bit stronger. The SS brakes are 4 wheel disc while the Caprice is disc and drum. The main difference in tow rating is caused by the sporty wheels and tires on the SS. The aluminum wheels and the tires are not rated to handle a 4,400# car plus a 5,000# trailer. They barely are adequate to handle just the car with passengers. If I recall the tire load rating allows me to hanlde up to 5,000# total weight, the car is 4,400 leaving only 600# payload. So that means me plus 4 passengers are easily over the rating, add a trailer and we got fun. Those low profile fat tires can't handle a decent load. the rims are also not rated for it.
My figures are probably off a couple hundred here and there but doesn't matter when we are talking 5,000# trailer.
It is clear the SS was designed for fun while the Caprice is a general purpose full size car which might include some towing.
So like I always say, just fixing one system on a vehicle to handle a load does not mean it can actually handle a load safely or legally. I laugh when I hear about guys who fixed their towing problem by adding air bags to their Toyota(for example) with a 4 banger so they can handle an 8,000# trailer. Yes you can move it, but warn me so I am nowhere near you when you need to stop or take a sharp curve.
Way to windy, so I'll call it good here.
Jim Henderson
The tow rating is based upon many factors which have been evaluated by the factory to provide "Satisfactory" service life and minimal warranty issues.
You can tow almost any weight with any vehicle as long as you have traction and don't physically destory the tow vehicle just hooking up. I once pushed a 30foot motor home uphill with my 74 Datsun truck with 1800 engine and 4 speed, I was young and stupid.
What the factory is figuring is that you want to be able to tow for longer than a couple thousand miles without having to rebuild your truck every few thousand.
The engine, tranny and axle ratio are part of the equation but if the frame, axles, or hitch cannot hold the load then you have a reliability and safety issue.
If the brakes are too small you got a liability issue. And way too exciting for me to drive.
If the cooling system can't handle the heat you got a problem.
Bearings in the axle have a big effect on load carrying capacity.
Shocks and springs are different for towing. Tires and wheels are higher rated for towing. Don't haul a 10,000# trailer if your truck has sporty wheels and nice car type tires with low load ratings.
The electrical system may also be different.
I probably missed a few things but in general just because you have a big engine does not mean you can tow for squat.
2 examples. The Old Chevy 454 sport truck had essentailly a truck engine right? Pretty similar to our workhorse 460s as far as tow power. But the 454 truck had a relatively low tow rating, I think something ludicrous like 2,000# or at best 5,000#. The reason the rating was so low was the brakes, axle bearings, springs and shocks, tires and wheels and maybe a couple other things. The truck was designed for fun and sportyness not towing.
An easier example. I have a 96 Impala SS. The standard base model would be a Caprice. The SS tow rating is only 2,000#, the Caprice is something like 5,000#. The engine and tranny and diff is essentially identical. The SS Frame is actually a bit stronger. The SS brakes are 4 wheel disc while the Caprice is disc and drum. The main difference in tow rating is caused by the sporty wheels and tires on the SS. The aluminum wheels and the tires are not rated to handle a 4,400# car plus a 5,000# trailer. They barely are adequate to handle just the car with passengers. If I recall the tire load rating allows me to hanlde up to 5,000# total weight, the car is 4,400 leaving only 600# payload. So that means me plus 4 passengers are easily over the rating, add a trailer and we got fun. Those low profile fat tires can't handle a decent load. the rims are also not rated for it.
My figures are probably off a couple hundred here and there but doesn't matter when we are talking 5,000# trailer.
It is clear the SS was designed for fun while the Caprice is a general purpose full size car which might include some towing.
So like I always say, just fixing one system on a vehicle to handle a load does not mean it can actually handle a load safely or legally. I laugh when I hear about guys who fixed their towing problem by adding air bags to their Toyota(for example) with a 4 banger so they can handle an 8,000# trailer. Yes you can move it, but warn me so I am nowhere near you when you need to stop or take a sharp curve.
Way to windy, so I'll call it good here.
Jim Henderson
Fleet Mechanic
Joined: Feb 2003
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Tow Ratings?
jim henderson hit the nail squarely on the head.
How does engine, trans, and rear axle ratio affect stability and braking?
A truck with a 1/2 ton tranny towing a 10,000 lbs load will overheat and destroy the tranny. Need a heavy duty, meaning 1 ton tranny.
If you order a HD truck with the same frame, springs, axles, brakes you get the same GVWR / GCWR whether you get a 250 hp / 950 torq engine or a 600 hp / 2050 torq engine and gear ratios play absolutely no role in ratings.
All things being equal, lower gear ratio gives you more towing capacity because you get higher RPMs at same (esp. lower) speeds.
If a typical class 8 truck can be rated 90,000 lb with only 470 hp / 1650 torq I fail to see why a 145 hp / 265 torq 4.9L I6 F150 would need it's GCWR reduced from 12,000 lb to 10,000 lb with the only change being the loss of the 5.8L engine (Same trans and rear axles).
These real trucks have lots and lots of gears and torque. They are diesel.
So if a 5.8L is safe at 12,000 lb GCWR why wouldn't a 4.9L be?
If everthing else is heavy duty - i.e.
suspension, rear brakes, rear differential, aux. tranny cooler, frame, wheels, and of course a really low real axle of at least 4.10 and lower, yes I think it is feasible to tow with that engine but you will be going really slow. Probably 25 mph on steep hills. In flat country, like Kansas, that's another matter.
That's why 1 ton F350 with 5.8L are slow and you really want 7.5 instead.
With these weights, you want either a big block gaser (my choice) or an equally good choice if you are really serious - diesel.
P.S. I have a plain jane Caprice with a towing package rated for 5,000, I towed about 3,000 lbs with it and it is working hard. I wouldn't even think to exceed 3K lbs. And this is a small block 5.7L. I have 3.23 rear. I wouldn't even use small block V8 let alone a I6 for towing these kinds of weights.
How does engine, trans, and rear axle ratio affect stability and braking?
A truck with a 1/2 ton tranny towing a 10,000 lbs load will overheat and destroy the tranny. Need a heavy duty, meaning 1 ton tranny.
If you order a HD truck with the same frame, springs, axles, brakes you get the same GVWR / GCWR whether you get a 250 hp / 950 torq engine or a 600 hp / 2050 torq engine and gear ratios play absolutely no role in ratings.
All things being equal, lower gear ratio gives you more towing capacity because you get higher RPMs at same (esp. lower) speeds.
If a typical class 8 truck can be rated 90,000 lb with only 470 hp / 1650 torq I fail to see why a 145 hp / 265 torq 4.9L I6 F150 would need it's GCWR reduced from 12,000 lb to 10,000 lb with the only change being the loss of the 5.8L engine (Same trans and rear axles).
These real trucks have lots and lots of gears and torque. They are diesel.
So if a 5.8L is safe at 12,000 lb GCWR why wouldn't a 4.9L be?
If everthing else is heavy duty - i.e.
suspension, rear brakes, rear differential, aux. tranny cooler, frame, wheels, and of course a really low real axle of at least 4.10 and lower, yes I think it is feasible to tow with that engine but you will be going really slow. Probably 25 mph on steep hills. In flat country, like Kansas, that's another matter.
That's why 1 ton F350 with 5.8L are slow and you really want 7.5 instead.
With these weights, you want either a big block gaser (my choice) or an equally good choice if you are really serious - diesel.
P.S. I have a plain jane Caprice with a towing package rated for 5,000, I towed about 3,000 lbs with it and it is working hard. I wouldn't even think to exceed 3K lbs. And this is a small block 5.7L. I have 3.23 rear. I wouldn't even use small block V8 let alone a I6 for towing these kinds of weights.
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Tow Ratings?
Both the 5.8L Auto and the 4.9L Auto use the same frame, trans, springs, brakes, and axle. The only difference is in the engine and possibly cooling system yet one is rated at 11000 GCW and the other at 12000 GCW (3.55 axle).
Also as I stated above the torque to weight ratio of my 1650 torq class 8 at 90,000 lb gross (Factory Rating) is the same as a 4.9L at 14500 gross.
Someone would really have to show me a lot of evidence to convince me a 4.9L is less durable at 12000 lb GCW than a 5.0L or 5.8L. Especially given the higher rating the 4.9L has in the F250. I would find it very hard to believe a 4.9L I6 is less durable than a 5.0L V8 in particular.
If the F150 chassis and E4OD is good for 12000 lb and the 4.9L is good for 12500 lb the question remains why when the two are combined does the GCW drop to 11000 lb.
In my opinion it is a marketing decision based on car people buying F150's which results in people who think a truck that slows on a hill is somehow inadequate for the given load.
I am used to a market in which you pick a chassis to handle a given load and then decide how much power you need/want. If it slows to less than 40 mph on a hill thats what flashers are for.
I really think we would be better served if light duty manufactures would rate the chassis and let the consumer pick the power.
Just my opinion. Don't no why I care as 5600 lb tow rating is just fine.
BTW according to a response from Ford to a inquiry I made GCWR does not actually exist. GVWR is a actual official rating but GCWR (and by inference tow rating) are only a suggestion. However if you exceed what they feel are reasonable limits it may void your warranty.
The situation seems to just get less and less clear.
I think I will just go back to my old rule of thumb:
1/2 ton = 5000 lb Trailer / 750 lb Pin
LD 3/4 Ton = 6000 lb / 1000 lb
HD 3/4 Ton = 7500 lb / 1500 lb
SRW 1 Ton = 9000 lb / 2000 lb
DRW 1 Ton = 10000 lb / 2500 lb
1.5 Ton = 12000 lb / 3000 lb
2.0 Ton = 14500 lb / 3500 lb
Anything more than this needs a real Medium Duty.
Always worked for me.
Also as I stated above the torque to weight ratio of my 1650 torq class 8 at 90,000 lb gross (Factory Rating) is the same as a 4.9L at 14500 gross.
Someone would really have to show me a lot of evidence to convince me a 4.9L is less durable at 12000 lb GCW than a 5.0L or 5.8L. Especially given the higher rating the 4.9L has in the F250. I would find it very hard to believe a 4.9L I6 is less durable than a 5.0L V8 in particular.
If the F150 chassis and E4OD is good for 12000 lb and the 4.9L is good for 12500 lb the question remains why when the two are combined does the GCW drop to 11000 lb.
In my opinion it is a marketing decision based on car people buying F150's which results in people who think a truck that slows on a hill is somehow inadequate for the given load.
I am used to a market in which you pick a chassis to handle a given load and then decide how much power you need/want. If it slows to less than 40 mph on a hill thats what flashers are for.
I really think we would be better served if light duty manufactures would rate the chassis and let the consumer pick the power.
Just my opinion. Don't no why I care as 5600 lb tow rating is just fine.
BTW according to a response from Ford to a inquiry I made GCWR does not actually exist. GVWR is a actual official rating but GCWR (and by inference tow rating) are only a suggestion. However if you exceed what they feel are reasonable limits it may void your warranty.
The situation seems to just get less and less clear.
I think I will just go back to my old rule of thumb:
1/2 ton = 5000 lb Trailer / 750 lb Pin
LD 3/4 Ton = 6000 lb / 1000 lb
HD 3/4 Ton = 7500 lb / 1500 lb
SRW 1 Ton = 9000 lb / 2000 lb
DRW 1 Ton = 10000 lb / 2500 lb
1.5 Ton = 12000 lb / 3000 lb
2.0 Ton = 14500 lb / 3500 lb
Anything more than this needs a real Medium Duty.
Always worked for me.
