Tow Vehicle Project

[MarkV]

I get real dense when it comes to figuring out vehicle towing capacities and need some help. I have a truck I would like to turn into my tow vehicle and before I start putting money into it I want to make sure it is up to the job and will be legal to work with. The towing would be local, occasional and non-business related.

Here are the basics. To be towed would be a 7000lbs tractor on an18 foot 10,000lbs trailer that weighs 2400lbs and has brakes on both axles. I figure that puts me right close to 10,000 lbs. by the time you add fuel, chains and whatever. The truck is a 1988 Chevy C30 dually with a 12 foot stake bed, automatic transmission and 6.2 liter diesel. This truck was originally an Air Force truck and has 40,000 original miles on it. The government identification plate riveted to the dash says the truck has a curb weight of 6120 lbs., a load capacity of 4500 lbs and a gross vehicle weight (max.) of 10,500 lbs. I would not know if the government sets any of its weights or restrictions differently than Chevy did and I also don’t know where I could find Chevy’s numbers for a truck this old configured this way.

So can anyone teach me how to figure out how much I can tow with this truck? If I don’t have all the needed information, any idea where I can find it?

Thanks in advance,
MarkV

 

[Highbeam]

Grab the VIN number and call GM. You want to know the Gross Combined Weight Rating, the GCWR. That number is where the tow rating comes from and all you will need to do is subtract the curb weight from the GCWR to get there. GM will know this and is your only real source. If you ever wrecked, your VIN would be used to dictate how much you should have been hauling. Make sure the person you call, not a dealer, wants to know the VIN and doesn't just ask if it is a one ton, dualluy, etc.

Chances are that the GCWR is pretty low. The 6.2 was a replacement for the small block and the combined rating is really a performance rating. I think you'll be unimpressed towing that trailer. The truck is very useful as a cargo hauler.

 

[JimR]

Your truck if equipped with the proper gear ratio rear end will pull that load with no problem. A friend of mine has about the same setup with a dump body. His truck has a 350 V8 and an automatic tranny. He hauls a 37 horse Cub Cadet with a loader and backhoe on a 10k trailer.

 

[Highbeam]

You'll have to decide early on here if you want to do what the ratings say or what you think the truck is capable of. The 6.2 never managed to be as good as the gas 350 unless someone hopped it up.

 

[dubba]

</font><font color="blue" class="small">( This truck was originally an Air Force truck )</font>

Have you tried to register or inspect it yet? Most military vehicles are not legal for road use.....

 

[MarkV]

Highbeam, great information and I though you put it very well. I never thought of calling Chevy. I’ll call and find out what the GCWR is. I suspect that you are right and this isn’t the vehicle to turn into a towing machine the way it is configured. You are not the first to imply that the 6.2 diesel is less than a great engine performance wise.

Jim I’ll see what the ratings are from Chevy. I am not sure I want to spend the money if I will not be legal with this engine setup.

Dubba, I am registered and have been for several years. This truck is straight Chevy so is not restricted like many military vehicles. Good point though.

Thanks for the input fellows. I am all ears if anyone else has any thoughts.

MarkV

 

[BarryinMN]

I have a '93 C3500 reg cab 6.5TD and 5 sp dually cab & chassis though. Has a 10' dump box on it for a empty weight of 9K lbs. The sticker in the glove box reads 12K GVW and 13.5K trailer GVW so combined @ 25.5K. The truck has a 4.11 rear axle and shows 52 mph @ 1800 rpm (engine torque peak.)

 

[KevinMcD]

Highbeam,
I believe the GCWR is the GVW (not the curb weight) of the truck plus the GVW of the trailer.
Mark, if you are calling GM, I would ask them if they can give you the tow rating for your configuration. Sometimes the numbers aren't as staight forward as they seem. And don't forget the "properly equipped" part. Properly rated hitch, brakes, etc.
Kevin McD.

 

[MarkV]

Barry, it sounds like you have the truck I need. Your towing capacity is what I would like to have. This would be easier if Chevy had listed the towing capacity on the id plate of mine though I think I understand why they didn't.

Kevin, from my reading on the subject I think Highbeam is right on with his terms. When you think about it Chevy sold this truck as a chassis to the goverment so they would not be able to say what kind of bed was going to be on the chassis. Without knowing that they can’t say what the tow rating would be. The GCWR is a combination of what the chassis can carry and tow combined based on the engine, tranny, axle configuration, suspension system, wheel base and gear ratio which Chevy can calculate. Once you have that number you can take the chassis with what ever is put on it, weigh it (curb weight), subtract that from the GCWR and you have the tow rating for that configuration. The GVW is what the chassis with whatever is on it can carry directly. Weigh it road ready (cub weight), subtract that from the GVW and you have load capacity but not towing capacity. In my case the GVW is 10,500, minus the curb weight of 6120 and you have a load capacity of 4380lbs.

How about it Highbeam, am I getting the idea? What I don’t understand is why the manufactures don’t list the GCWR on the id tag. Also with out that rating how does DOT determine if you are hauling heavy when they pull you over?

I’ve e-mailed Chevy with VIN number in hopes of getting the GCWR. We will see what happens.

Thanks,
MarkV

 

[Highbeam]

That's perfect Mark, you've got it. Sometimes when you buy a chassis/cab the manufacturer lets you assign a GVWR. The chassis/cab is considered an incomplete vehicle so the GVWR needn't be assigned by GM. This is why you see RV folks buying chassis/cabs and putting a truck bed on so that they can have their "builder" legally set their GVWR where they want it. The incomplete status of a chassis/cab may also lead you to trouble getting info from GM. But this isn't a bad thing since if GM doesn't know the GCWR then noone knows it.

It has been said that if you respect all numbers on all stickers on the truck and trailer that the DOT can't get you on a number law. Instead, they'll try some kind of subjective law like "unsafe load". The GCWR, being a performance rating, isn't linked to safety in the same way that axle ratings and GVWR ratings which directly relate to bearings, frame, and brake capacity. Still, GM usually knows your GCWR and in a fatality wreck someone will check it. If you find the GCWR, I think it is wise to add it to the label on your truck so you can remember it.


"I believe the GCWR is the GVW (not the curb weight) of the truck plus the GVW of the trailer."

Sort of, GVW is the curb weight(Gross Vehicle Weight). I think you meant to say that GCWR is the limit of the sum of the GVWRs (Gross Vehicle Weight Rating) of both truck and trailer which is very much not true. The GCWR rating is a limit on the sum of all axle weights of your combination.

The tow rating is a mumbo jumbo marketing number based on assumptions along with the GCWR and curb weight of a stripped down empty tow vehicle.

 

[George2615]

I have an 05 Chev 2500HD with Duramax and Allison trans. and 3.73 axle. My GVWR is 9200, Max trailer wt. is 12000 w/ ball hitch or 15500 w/5th wheel hitch, GCWR is 22000. The owners manual does not list the 5th wheel trailer weights. I could not find the owners manual from the 88 Chev. I owned years ago. (It's probably still in it). I don't think your C30 Dually would have any problem towing 10K. Since it was a military vehicle I'm also sure it was built to haul a big load. If your GVWR is 10500 it's rated more than mine and the GCWR would also be higher than mine. Hope Chevy has an answer for you.

 

[BarryinMN]

I figured my '88 & newer bodystyle is the same as yours so hardware and numbers maybe similar.

Since the truck is over 10K and the trailer is 12K I have DOT safety inspection stickers on both, DOT # on pickup, and a DOT medical card. I use it exclusively as a hobby farm private use no CDL is required. The over 10K trailer drives the medical card in MN.

As others stated the power is 1/2 what is sold these days. I just keep it stock: solid, stable, reliable platform have towed through snow, ice, rain, etc. My heaviest machine is 10K so I do use the capacity.

I had a friend with a well used '88 Suburban with the 6.2 who towed a large sailboat slow but got the job done. He did like the gas mileage though.

 

[MarkV]

Haven’t heard anything from GM yet. That doesn’t exactly surprise me. I am going out of town until the middle of next week so I will check when I get back. Thanks for the additional input.

MarkV

 

[Builder]

Actually, power is probably the least important factor when determining the towing capacity of a vehicle. Most important are brakes & supension/ frame/tires and hitch ratings.

I've had my CDL for quite some time and have hundreds of thousands of miles seat time in bigger trucks so maybe this example will show you what I mean:

My first over CDL truck was a 1979 IH1700 10' dumptruck. It had a GCWR of 60,000lbs and a GVWR of 30,000lbs. The engine was a 345 gas V-8 with only 185HP. It had less horepower and torque than my 1991 F-350 pickup. In fact it had less horsepower than my wife's minivan! The difference was the brakes and frame/suspension. Massive in that department, it could stop the 15 ton tag and backhoe I towed behind it. It did the job and stopped the trailer safely.

To answer the original question, I would think you'd be fine towing a 10K trailer behind a dually 30 series stakebody. It will be slow as molasses behind a 6.2L, but it will get the job done. Just try to find out the GVWR from GM. Shouldn't be a problem.

One area of deception by GM, Ford & DC you need to watch out for is MAX tow ratings: most of these ratings are 5TH WHEEL ratings, not conventional tow ratings. The 5th wheel ratings are of course much higher, since the load is moved over the rear axle, not behind it. A lot of guys will tell you their truck "can tow 15,000 lbs", but that's 5th wheel. The conventional ratings are thousands lower. So when you get your GCWR number back from GM, that doesn't mean you can tow the same load off the back of the truck as you can with a 5th wheel.

Make sure you have a truck shop attach the proper hitch to your truck and make sure they certify the truck to tow the load you specify to them. You'll notice most body companies will affix a small decal next to the hitch that will show max TOW capacity and max PIN weight. That's what the MVEC will look for when they stop you. Also make sure you have a med card (required when operating a combination of vehicles over 17,000lbs) and make sure your registration has enough weight on it to cover the truck & trailer. If your trailer is under 10,000lbs, most states don't require you to register your combination weight on your registration.

The company that adds the secondary truck body to the chassis determines the final GVWR of the truck. The GCWR is determined by the manufacturer of the vehicle. With the exception of adding an airlift axle or additional suspension components, no secondary body company can re-rate a truck to have a greater GCWR than the original manufacturer, which in this case is GM.

Just because the military originally spec'ed the vehicle does not mean it can tow a lot of weight. the military may have built that truck simply to be a stakebody that wasn't used to tow a trailer.

I deal with this stuff on a weekly basis and have MVCE cops as friends. They tell me what they look for, so ask away and i can try to help you avoid the pitfalls.