What determines GVW?

[396C20]

Hi all,

I am trying to figure out what my truck is able to carry/tow. I get that the GVW is the total weight of the truck and contents my question is, is it the suspension or tires that determine that number? The reason I ask is my 69 has a GVW of 7500, the truck weighs 4800# so that only gives me a 2700# payload is that right? So if I want to tow my 3000# car on a 2000# trailer I would be overweight? If that is the case how does one increase the rating?
Thanks in advance.

[cdowns]

no GVW is different than towing capacity// you're trailer and car would only add the tounge weight of the rig to your GVW// GVW is the weight you're carrying on your 4tires

[junkyardjohn]

I Could Be Very Wrong Here, & If I Am Somebody Please Correct Me. I Always Thought That The Tongue Wieght Was What You Added To The Weight Of Your Truck To Tell If Your Truck Was In The Parameters Of The Gvw. In Other Words.. I Thought The Gvw Was How Much You Could Safely Carry & Not How Much You Could Tow. I Have A C-30 Stake Truck With A 14,000 Lb Gvw While My C-30 Tow Truck Has A 10,000 Lb Gvw.

Like I Said.. I Could Be Wrong... Will Someone Please Enlighten Me?? . John

[junkyardjohn]

DAMN SLOW FINGERS. THANKS CDOWNS. JOHN

[396C20]

Thanks guys, I knew I was missing something in the equation.

[Longhorn Man]

CGVW includes the trailer... but that wasn't done back then.
Your GVW indicates you can haul well over a ton in your truck if it is distributed properly.
There's a few answers to your question... the legal one, wouyld be nothing. You could put one ton frame/tires/springs etc under your truck, but legally, as long as your GVW plate reads 7500, then that is all you are able to haul.
Now, for a technical answer, the gearing, springs and tires covers most of the GVW requirements for thes rigs for back in the day. Modern standards would include brakes moreso than anything.
While not asked, it is on the same topic, GM figured the GCW, Gross Combined Weight (same as CGVW) by the Designation of the truck (C/10, C/20 etc) the engine size, and the rear gearing. On your truck, being a big block and 3.54 gearing, you are good for a combined weight, that's everything in, on, and towed by your truck, of just over 10,000 pounds.

[396C20]

Thanks Longhorn, So it looks like I am right at the limit.
A few more questions.
I hope I’m not getting to anal here but if the tires are rated for load range E @ 3042 each can I assume the wheels need to be rated equally to reach that rating? I have seen some of the steel wagon wheel types only rated for 2000#.
And the obvious question just because the tires together have a load capacity for 12,000 does that mean I would be safe/legal with that weight?
Also you mentioned braking abilities are now considered in the GCVW. Again in the interest of safety is the stock power brake setup adequate for the weights mentioned previously?
One other note, if I lower the gear ratio will that necessarily increase the GVW?
Thanks again for your input.

[Longhorn Man]

While i am sure there are weight limits on wht wheels... I am not aware of them, nor how to find them.
12k load on the tires.. but eh springs aren't rated for that, and in all reality, nor the frame 'technicly' anyways.
In comparison to modern brakes, the drums we have are so poor it is unreal. However, with that being said, if you have a tralor brake, and you aren't stupid on how you drive, you are safe where you are at, and again, you could do more with it, just not legally.
The listing I have from GM does not show the 396 with any other gearing in a 3/4 ton, and it does not show one ton trucks. It actually shows a 350 with 4.10 and 4.56 gearing as able to tow more... so, in theory, yes, installing a 4.10 gearset would increase your CGVW.

[mtdave2]

I have been playing with this lately too. Ya you are right about how much your truck can carry. And no you would not be over weight with your trailer. Don’t for get your trailer has a gvw rating too. You add the two numbers together (gvw of truck and trailer) subtract the light weights and then you have your max about of weight you can carry.

As for how much weight you are putting on your truck.. if you load it correctly you should have around 10% of total trailer weight at the tongue. So your 3000 pound car and 2000 pound trailer gives you 5000 pounds. 10% of that should give you 500 pounds on your truck. Well under your capacity.

i just bought a trailer with a 10,000 pound gvw. it weighs 3000 pounds, giving me 7000 pounds i can carry. i can figure 10% of that for tongue weight of 700 pounds.

my truck has 7500 gvw and it weighs 4200 pounds. That’s 3300 pounds i can carry in it.

now if i combined them, 7500+10000=17500, i would get a ticket if the dot weighed me and i was over that amount.

bottom line for me in real life. i can put 6000k on the trailer and have a litter margin for error. Will my truck do it? Not very well at the moment, but im working on getting more power!

[Aarons72s]

Here is a question I think on the same lines. If you upgrade everything to a higher GVW could you have the truck recertified (by the state) to a higher GVW? Lets say you rebuild a 1/2 ton to 3/4 ton, could you get it recertified a 3/4 ton? Just a thought.
Aaron

[junkyardjohn]

NOPE.. NO STATE THAT I KNOW OF WILL RE CERTIFY OR CHANGE YOUR GVW NO MATTER WHAT YOU DO TO IT. THERES AN AWFUL LOT OF LIABILITY THERE, & NOBODY WILL GRANTEE WHAT YOUR TRUCK WILL HAUL UNLESS IT'S A HO-MADE OR REBUILT VEHICLE, & THEN MAYBE A PROFESSIONAL SHOP WILL CERTIFY IT FOR MANY MANY $. JOHN

[Longhorn Man]

I have to agree. The only way to do it would be to swap the VIN plate... which raises it's own questions.