Regular vs Big 10

[87Bob]

I have a bone stock, low option, long box, 1985 C10 305cid 350. I don't plan to lower it or raise it. It is my around the house hauler. I do plan to trick it out a little. I just bought a set of used 8" wide Rallies to refinish and put on it. I have a late model Blazer 4 headlight front end to put on it. It has a tool box which I have had media blasted and is ready for paint. It has a few dings and dents and a little rust and eventually will need paint. Some of the other up grades that are planned is vintage air, an extang tool box tonneau cover, new chrome step bumper, interior redo and a stereo upgrade. Mechanically I'd like to build a torque monster 383 with a gear vendors over/under drive so I can use it to pull a enclosed car trailer. It is just a common everyday driver. Since I do use it to haul loads I saw in another post a reference to a "Big 10" having more leafs in the springs is that to haul heavier loads and pull more weight? Has anyone beefed up a 1/2 ton to give it better weight caring and pulling capacity? I'm looking for suggestions here. Thanks!

[Pyrotechnic]

The "Heavy Half" and "Big 10" or "heavy duty chassis equipment" option for the most part is 3/4 ton springs with a 5 lug rear axle and 5 lug front rotors.

Parts of the package:
3/4 ton front springs
3/4 tons rear springs (several inches longer than 1/2T springs, shackle hanger location is further back on the frame)
Wider rear brake drums and shoes for better stopping ability
2 piece drive shaft for long beds
Double hump transmission crossmember for true dual exhaust (no cats)
Very minimal emissions equipment

A lot of the time, I think GM created these trucks as a loop hole. By upping the GVWR with the 3/4 ton springs, it bumped these trucks in the non emissions category the usual emissions garbage and catalytic converter don't have to be there. However, they really are better for hauling, towing, etc.

[dooce]

is the double hump crossmember the same one used on the 4x4s?

[old Rusty C10]

the springs are the longer set but there are regular half tons that have the longer less leaf leaf springs ive had both kinds

[spr85gmc]

Pics of the truck thinking about picking one up for 800 .00 complete and running

[Captkaos]

They also had HD front brakes.

[seanconnery]

And HD front brakes means 1 1/4 inches, and not 1 inch right? Is there a leaf count to how many leafs come in the "heavy duty" package?

[N2TRUX]

Originally Posted by 87Bob

.... Has anyone beefed up a 1/2 ton to give it better weight caring and pulling capacity? I'm looking for suggestions here. Thanks!

My suggestion would be to add a set of helper air bags. They will allow you to add as much or as little assistance as you need to carry the load. They work great with an on-board compressor, or you can run schrader valves and fill them with a portable air supply.

I have had this set up on two different trucks and it worked awesome.

[Captkaos]

Most HD rear leafs had either 7 or 9 leafs, all of them were 56" long.

[87Bob]

Originally Posted by N2TRUX

My suggestion would be to add a set of helper air bags. They will allow you to add as much or as little assistance as you need to carry the load. They work great with an on-board compressor, or you can run schrader valves and fill them with a portable air supply.

I have had this set up on two different trucks and it worked awesome.

The air bag helpers I've seen go out side the frame have they presented any problems with wheels rubing?

[78 Big10 454]

I bought my 78 half-ton Big 10 new in December, 1977. It has nine 56" long rear leaf springs. Even though it's a shortbed, it has the two piece driveshaft. Unfortunately, it was not exempt from California smog regulations, so I have cats on the dual exhaust system.

[seanconnery]

Is it safe to say that if you have a 250 inline 6, then you probably don't have the "Big 10", or "heavy half" options?

[dswancutt]

Couple of minor corrections I would like to point out. ALL 73-80 1/2 chevys have the big rotors. The smaller rotors didn't start until 81. I have looked in the chevy parts manual and have confirmed this. What the Big 10/Heavy Half gets you is the double diaphragm booster, 2/ 3/4" wide rear brakes.
My 78 Big 10 does not have the 2 piece drive shaft or double hump crossmember, and it is the last year for the no smog trucks.
And you could get the Big 10/Heavy Half with any engine package.
And as far as helping with pulling a trailer, it will. I also have a 79 that is a 6 cylinder and has the heavy rear spring option and a bumper pull stock trailer barely even sags it.
Hope this helps.

[seanconnery]

dswancutt, it does help, but it keeps me asking more questions. Is there a description or a code on the sticker inside the glovebox in these trucks that will settle this once and for all? Mine happens to be a 1981 GMC Sierra Grande. Is this code (if there is one) applicable to all 73-87 trucks?

[dswancutt]

My knowledge base pretty much is limited to the 73-80 years. For a big 10/heavy half, the 4th digit of the vin # will be a 4 (example CCL4). If you find a truck with the options sheet still in it, it will be the 1F44 package.
Since yours is an 81, I would imagine that it has light duty equipment on it, but there is an outside chance that in might have the F44 package as the code ran from 76-81.

[87Bob]

Ok now I'm more confused than ever. But I have learned a couple of things.
Please feel free to comment.

I need to get better braking front and rear.

*Larger Rotors and Calipers for the front. Does this require new spindles?
*Larger Rear Drums (2-3/4 wide shoes) Will these fit on my current rear
axle?
*Do I need to change the Power Brake Booster/Master Cylinder?

For supporting the load I need to change to a 3/4 ton set of springs or get a set of air bag helpers.

[Captkaos]

Heavy Half as stated will have 4 in the 4th digit of the VIN, 6th on 81-87's

HD brakes is what everyone associates with the 1.25" rotors so I used it generically.
As stated all 73-80's had these rotors standard. 81-87's had 1" Standard brakes and are the "low drag" brakes.

We are talking about making an 85 a Heavy Half, so it would have HD front brakes in addition to the HD rears Pyro pointed out, which comes with dual diaphragm booster.

If you have an post 80 and you want it to be equipped like a Heavy Half, you need all of the following:
HD suspension:
3/4 ton front springs
3/4 tons rear springs (56" long - 7 leaf)
HD Brake system:
HD 1-1/4" Front rotors
HD Dual diaphragm booster
HD 2-3/4" rear brake drums and shoes for better stopping ability
Minimal emissions equipment (you won't get away with this without the 4 in the VIN)
Larger Tires
Heavy Half would be available in any engine config, but it would effect the GVW rating.

Adding the 3/4 springs to the truck WILL alter the height along with the larger tires.

No 1/2T 81-87's came with duals, the only ones were K30 4x4 and Crew Cabs.

Originally Posted by 87Bob

Ok now I'm more confused than ever. But I have learned a couple of things.
Please feel free to comment.

I need to get better braking front and rear.

*Larger Rotors and Calipers for the front. Does this require new spindles?
*Larger Rear Drums (2-3/4 wide shoes) Will these fit on my current rear
axle?
*Do I need to change the Power Brake Booster/Master Cylinder?

For supporting the load I need to change to a 3/4 ton set of springs or get a set of air bag helpers.

HD brakes require new rotors and spindles. ( I can't remember on the caliper, but I think they 81-87's were different)
Rear: The backing plate is the same, everything else isn't, sans the wheel cylinder, as I am not 100% sure.
Do you NEED to change the booster, no. But the HD version is the dual diaphram version.

[TeamRinaldi]

I've got an '85 heavy half. Like the other guys said, it's essentially a 1/2 ton with a 3/4 ton setup under her skirt. I'll get the option codes out of my glove box in the morning. It's got a 305/350/2:73's (for now) and has the heavier front disks and rear spring setup. It sits a little higher in the rear then some of my buddies trucks, but under load doesn't move. Well, I had it REALLY loaded down once and it sat nice and level.

[87Bob]

I appreciate all the responses. My Truck is a long term project. I bought from my father in law for those times I needed to haul something around the house. The secret is that I have a 2 and a half year old Grandson that I plan to redo it for. That way he can have something that belonged to his great grandpappy. Carter, my Grandson loves all things mechanical you ought to see him on my John Deere 2020. Anyway when I get it done he'll have a good ole boy pickup. Since he lives in North Carolina it will fit right in. One of my hero's trucks is Slonaker's. Simple Sweet and clean!

[crosscountry]

I have a 74 cheyenne super/10 it has 8 rear leaves counting the thick over load on bottom.. I got it for hauling a 20" box trailer crosscountry two times a year, does very well... it had a 2.73 originally but I changed it to a 3/4- 4.10 non full floating axle out of a suburban. I carry two spares only drawback...
It was originally a 454 I pulled it and installed a Gm/mexico 350 4bolt main long block, used original 400 tranny and new 454 radiator it had a factory trans cooler..
Ok enough backgroung...
The 4th vin # is a 1 not a 4 the 5th digit is a 4 so the chassis is a standard 1/2 corrrect???
the tag on door post says 6000lb GVW.. I think it may have had an optional load package since it had trans cooler and heavy rear springs....

[79gmcsierragrande]

Thanks for posting all that, it answered a lot of questions I had about my heavy half. I love this site.

[staggerd86c-10]

my 86 c-10 had 7 leaves in it, does that mean it was the heavy duty rear? i have taken out the overload spring and one of the lower ones and i still have 5. do you guys know how much drop i will get if i take out one more leaf? its still a bit higher in the back and its driving me crazy

[Captkaos]

Originally Posted by crosscountry

I have a 74 cheyenne super/10 it has 8 rear leaves counting the thick over load on bottom.. I got it for hauling a 20" box trailer crosscountry two times a year, does very well... it had a 2.73 originally but I changed it to a 3/4- 4.10 non full floating axle out of a suburban. I carry two spares only drawback...
It was originally a 454 I pulled it and installed a Gm/mexico 350 4bolt main long block, used original 400 tranny and new 454 radiator it had a factory trans cooler..
Ok enough backgroung...
The 4th vin # is a 1 not a 4 the 5th digit is a 4 so the chassis is a standard 1/2 corrrect???
the tag on door post says 6000lb GVW.. I think it may have had an optional load package since it had trans cooler and heavy rear springs....

What I was posting about applies to 81-87's.
A 73 with 1 in the 4th posistion is a normal 1/2T, the 5th digit being a 4 means it is a pickup. If it is a long bed and a 73/74 I wouldn't doubt it has more leafs. Typically the 73-80's had 8/9 leafs.

[TeamRinaldi]

Sorry it took so long, but here's the codes from the glovebox.

1G50 : Heavy duty rear springs
1J55 : Heavy duty power brakes

Thing is, now that I'm doing a little more legwork I'm not sure if I have what I think I have (if that makes any sense). I've decoded the vin and all looks ok, I'm just wondering if maybe I have a very well optioned (the sheet is really long) C-10, instead of a "true" heavy half. At any rate, hope this helps a little.

[Captkaos]

TeamRinaldi, based on you option sheet I would imagine that you have a 4 in the 6th digit of the VIN on your 85.