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Old 05-12-2005, 12:15 AM   #1
karl
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What is a Big 10 or Heavy half?

i just purchased a 77 half ton pickup and the 4th digit in the vin is a 4. the gross weight for this truck is 6050 lbs. this makes it a Big 10. this is a calif. truck but no cat converter. also the intake manifold(v-8) dosent have an egr valve. is this correct? or do all trucks regardless of weight require an egr valve? what are emissions for the heavier trucks? thanks
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Old 05-12-2005, 12:48 AM   #2
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My 1977 Scottsdale I had in high school was vin CCL4471123669 . It was a Short Bed , 350 Non-EGR , non Air Cond .Truck . It was ordered with a 3.07 rear and a locker . Mine was the only truck I have seen (or maybe the only one I payed attention to ) that didnt come with an EGR valve and it also did not have Cats in the exhaust system . The trans crossmember did not have the same shape as trucks with factory cats . Too bad that you have that truck in Cal. They will probably make you change it to meet the local laws . Frank
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Old 05-12-2005, 09:13 AM   #3
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I wish the search function was working. Someone posted a great write up on the diffreces off the BIG10 by year a couple months ago.

Basicaly in the first couple of years the BIG10 was the way that GM got around smog requirements on a 1/2 ton.

The weight limits on the truck were rased just above the cut off for smog equipment.

I believe after 1979 the weight limit was rased which brought the BIG10 back into smog requirements.

Once the search function is enabled again do a search on BIG 10 and look for the write up. It was the best information on a BIG 10 I have ever seen.
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Old 05-12-2005, 09:41 AM   #4
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I found the write up as posted by KIILEW:

Buckshot:

Concerns like yours about selecting the right vehicle for cargo carrying requirements, and more specific interest in the Big 10 occasionally appear in these forums, so I thought I would throw in my two cents worth. I see you posted your question a long time ago, so you may have already decided, but perhaps some of the following info might be useful to others.

As others on this board may note, brevity is not my forte. Most of this stuff is probably not worth wading through for your purposes, but maybe somebody can find something of interest (or contention) in it.

Some Big 10 history:

The Big 10 was promoted as a heavy duty two wheel drive half ton for the 1975 through 1980 model years. Although it offered truck buyers somewhat more load carrying ability than the standard C10 half tons, its real advantage- -and the motive behind its conception- -was that it provided buyers with the opportunity to purchase a half ton truck that was unencumbered by the dreaded catalytic converter, which was first introduced to a skeptical American car buying public just in time for the 1975 model year.

For several years prior to that time, all trucks with gross vehicle weight ratings of 6,000 lbs and below were forced to comply with the strict “light duty” emission standards that also affected passenger cars. The EPA’s selection of the 6,000 lb. threshold likely reflected its awareness that that number had become the traditional de facto dividing line between half ton and three quarter ton trucks. And since the vast majority of trucks purchased by consumers were half tons, limiting the emission constraints to them probably seemed to be a reasonable compromise to the government, while avoiding potential protests about cost and implementation by the truck manufacturers- -and their commercial customers- -that might have occurred had the laws been expanded to the heavier vehicles.

Before the advent of the catalytic converter, the distinction between “light” and “heavy” duty emission controlled trucks was largely ignored by consumers. But the converter’s introduction and it’s nearly universal application in 1975 “light duty” emission vehicles changed things dramatically. Unlike the EGR and evaporative canister devices that preceded it, the converter had an exclusive appetite for expensive unleaded fuel which outraged truck buyers- -and especially fleet purchasers- -in a nation that still had access to relatively cheaper leaded fuel.

Recognizing a new marketing opportunity, or necessity, light truck makers made relatively minor spring, tire, and brake modifications to their existing half ton models to push GVWR’s just over the 6,000 lb. threshold. Ford lead the way by introducing the heavy half ton F150 as an alternative to their traditional half ton F100, while Chevrolet introduced the “F44 Heavy Duty Chassis” package as an option for their C10 pickup.

These new-for-1975 models moved into the “heavy duty” emission classification enjoyed by three quarter ton and heavier rated models. This allowed the F44 equipped C10, later dubbed the “Big 10” for market visibility, to comply with government emissions regulations using only a PCV valve, heat stove, and relatively loose “controlled combustion system” (CCS) tuning. In contrast, the 1975 “light duty” emission certified standard capacity C10 required a PCV valve, heat stove, stricter “controlled combustion system” (CCS) tuning, EGR, evaporative canisters, a vacuum activated early fuel evaporation (EFE heat riser) valve, special outside air ducting to the air cleaner, and a catalytic converter. But by 1979 the EPA- -following legislation enacted in California a year earlier- -raised the light duty/heavy duty emission dividing line from 6,000 to 8,500 lbs. GVWR which brought all heavy duty half ton and almost all three quarter ton pickups into the light duty emission fold. Following this legislation, consumer appreciation for the heavy duty half ton concept- -so gelded- -largely faded away.

A look at the chassis component differences that distinguish C10’s, Big 10’s, and C20’s:

What does this have to do with hauling around cement blocks? Well, let’s redirect the discussion to some component specifications for standard half ton C10’s, heavy duty half ton Big 10’s and three quarter ton C20’s. Note that the following pertains only to two wheel drive vehicles.

A careful study of the 1975 Chevrolet Light Truck Data Book provides some insight here. Leading into 1975 the regular (i.e. not heavy duty) C10 pickup offered several different GVWR packages. Those ratings were 4,900, 5,300, 5,400, 5,600, and 6,000 lbs. Beyond this, the new F44 Heavy Duty Chassis package provided a 6,200 lb. GVWR. Mid way through the model year, Chevy broadened the F44’s choices by adding a 6,050 rating option to the existing 6,200 lb package. This late-availability 6,050 pound option replaced the C10’s 6,000 lb. package, which was cancelled.

All seven of these C10/ Big 10 GVWR packages used the same basic frame with a side rail width, depth, and thickness of 2.30”, 5.92”, and .156” respectively. The frame section modulus was 3.14. Also, all of these packages utilized the GM 12 bolt semi floating axle with a capacity of 3,750 lbs., and used a standard 15”x6” five lug wheel rim. Differences in GVWR were attributable to choices in spring and tire capacities, and brake system components. Some engine and transmission option recommendations/restrictions also accompanied different GVWR offerings.

The base 4,900 lb. rated C10 used the following components at minimum:
• 1,550 lb. capacity front springs.
• 1,550 lb. capacity rear springs (consisting of 4 leaves, and having a length of 52” and a width of 2.5”).
• Front and rear tires with a load capacity of 1,470 lbs.
• Manual brake system (the 4,900 lb. rated C10 was the only pickup in the entire C/K10/20/30 lineup to use manual brakes. The front disk brakes had a diameter of 11.86” and a thickness of 1.28”. Rear brake drums measured 11”x2”).
• Standard LD4 250 1 bbl. I6 engine w/M15 Saginaw 3 speed manual transmission.

The 5,300 lb. GVWR required the following minimum additions and/or substitutions:
• Option code J50 light duty power brake system (front disk and rear drum specifications remained the same as shown above).
• Option code M20 Chevrolet CH465 4 speed manual transmission (recommended at 5,300 to 6,050 lb. GVW levels when LD4 250 1 bbl. I6 engine was selected; M15 3 speed manual transmissions remained available w/larger engines).

The 5,400 lb. GVWR required all items necessary for the 5,300 lb. rating plus the following minimum additions and/or substitutions:
• Front and rear tires with a load capacity of 1,610 lbs.

The 5,600 lb. GVWR required all items necessary for the 5,400 lb. rating plus the following minimum additions and/or substitutions:
• Option code G50 heavy duty rear springs (2,000 lb. capacity for this application. These springs consisted of 8 leaves, and were 56” long x 2.5” wide).
• Front and rear tires with a load capacity of 1,790 lbs.

The 6,000 lb. GVWR required all items necessary for the 5,600 lb. rating plus the following minimum additions and/or substitutions:
• Option code F60 heavy duty front springs (1,625 lb. capacity for this application).
• Option code J55 heavy duty power brakes (this system replaced the lighter capacity J50’s single diaphragm brake booster with a dual diaphragm unit and included larger 11.15”x2.75” rear drum brakes for C10 applications).

The 6,050 lb. GVWR package, which represents the lower of two F44 Big 10 capacities, was specifically identical, in terms of chassis and suspension components, to the 6,000 GVWR package which it superseded mid-year. Gross axle weight ratings at this GVWR were 3,100 lbs in front and 3,580 lbs. in the rear, and are the same as those cataloged for the 6,000 lb. model. The 50 lb. increase in GVWR appears to be a result of “on paper only” engineering. Emission control equipment was the only significant difference between the 1975 6,000 lb. and 6,050 lb. packages.

The 6,200 lb. GVWR was the maximum F44 option, and required all items necessary for the 6,050 lb. rating plus the following minimum additions and/or substitutions:
• Front and rear tires with a load capacity of 1,900 lbs.
• Option code LS9 350 4 bbl V8 engine w/M15 Muncie 3 speed manual transmission.

A similar breakdown can be made for the C20 regular cab pickup, which was available for ’75 with GVWR’s of 6,400, 7,100, 7,500, and 8,200 lbs. All four of these GVWR packages shared a frame with a side rail width, depth, and thickness of 2.30”, 5.92”, and .194” respectively. While the side rail width and depth were the same as the C10/Big 10 frame, the thickness was greater, and in fact was the same as the thickness of the frame used in the one ton C30. Not surprisingly, the frame section modulus, at 3.92, was also more robust. Finally, all of these packages utilized the GM 14 bolt full floating axle with a capacity of 5,700 lbs., and used a standard 16.5” eight lug wheel rim.

The base 6,400 lb. rated C20 used the following components at minimum:
• 1,750 lb. capacity front springs.
• 2,000 lb. capacity rear springs (consisting of 8 leaves, and having a length of 56” and a width of 2.5”).
• Front and rear tires with a load capacity of 1,990 lbs. (These used a 16.5x6” rim.)
• Power brake system with a dual diaphragm booster. (The front disk brakes had a diameter of 12.5” and a thickness of 1.28”. Rear brake drums measured 11.15”x2.75”.)
• Standard L25 292 1 bbl. I6 engine w/M15 Saginaw 3 speed manual transmission.

The 7,100 lb. GVWR required the following minimum additions and/or substitutions:
• Option code G50 heavy duty rear springs (2,600 lbs. for this application. These springs consisted of 9 leaves and were 56” long x 2.5” wide).
• Rear tires with a load capacity of 2,350 lbs.
• Option code M20 Chevrolet CH465 4 speed manual transmission (recommended at 7,100 to 8,200 lb. GVW levels when L25 292 1 bbl. I6 engine was selected; M15 3 speed manual transmissions remained available w/larger engines).

The 7,500 lb. GVWR required all items necessary for the 7,100 lb. rating plus the following minimum additions and/or substitutions:
• Front and rear tires with a load capacity of 2,780 lbs. (These used a 16.5x6.75” rim.)
• Option code J55 heavy duty power brakes (this system included larger 13”x2.5” rear drum brakes for C20 applications).

The 8,200 lb. GVWR was the maximum rating available for the C20 and required all items necessary for the 7,500 lb. rating plus the following minimum additions and/or substitutions:
• Option code F60 heavy duty front springs (1,900 lb. capacity for this application).
• Option code G51 extra capacity rear springs (2,850 lbs.).

What they will carry:

To assess the load carrying ability and overall stamina of each of these C10/Big 10/C20 GVWR levels, let’s calculate the payload that each GVWR can handle. This requires subtracting the curb weight of the empty vehicle from the gross vehicle weight rating. To eliminate some of the variables bearing on curb weight calculations and thus facilitate comparisons between the different GVWR/payload packages and series, let’s assume that all vehicles referenced below are optionally equipped with the LS9 350 4 bbl. V8, M40 Turbo Hydra-matic 350 transmission, N41 power steering and an appropriately sized spare tire. (The Turbo 400 transmission was available only with the 454 engine option on these vehicles.)

The payload of a C10 Regular Cab Fleetside with 8’ box, 4,900 lb. GVWR, and the above options would be calculated as follows with vehicle and optional equipment weights taken from the 1975 Chevrolet Light Truck Data Book:

Gross vehicle weight rating (lbs.) 4,900
Curb weight (lbs.) 4,014
Payload (lbs.) 886
…or 3 150 lb. people (using GM's favored methodology) and about 11 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with a 5,300 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 5,300
Curb weight (lbs.) 4,034
Payload (lbs.) 1,266
…or 3 150 lb. people and about 20 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with a 5,400 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 5,400
Curb weight (lbs.) 4,047
Payload (lbs.) 1,353
…or 3 150 lb. people and about 23 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with a 5,600 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 5,600
Curb weight (lbs.) 4,120
Payload (lbs.) 1,480
…or 3 150 lb. people and about 26 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with a 6,000 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 6,000
Curb weight (lbs.) 4,148
Payload (lbs.) 1,852
…or 3 150 lb. people and about 35 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with the F44 package and 6,050 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 6,050
Curb weight (lbs.) 4,124
Payload (lbs.) 1,926
…or 3 150 lb. people and about 37 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with the F44 package and 6,200 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 6,200
Curb weight (lbs.) 4,142
Payload (lbs.) 2,058
…or 3 150 lb. people and about 40 cement blocks at 40 lbs. apiece.

The payload of a C20 Regular Cab Fleetside with 8’ box, 6,400 lb. GVWR, and the options noted above would be calculated as follows

Gross vehicle weight rating (lbs.) 6,400
Curb weight (lbs.) 4,425
Payload (lbs.) 1,975
…or 3 150 lb. people and about 38 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with a 7,100 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 7,100
Curb weight (lbs.) 4,463
Payload (lbs.) 2,637
…or 3 150 lb. people and about 55 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with a 7,500 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 7,500
Curb weight (lbs.) 4,580
Payload (lbs.) 2,920
…or 3 150 lb. people and about 62 cement blocks at 40 lbs. apiece.

The payload of the same vehicle with an 8,200 lb. GVWR would be:

Gross vehicle weight rating (lbs.) 8,200
Curb weight (lbs.) 4,594
Payload (lbs.) 3,606
…or 3 150 lb. people about 79 cement blocks at 40 lbs. apiece.

Perhaps the most interesting comparison occurs between the C10 w/F44 6,200 lb. package, and the C20 w/6,400 lb. package. Despite the fact that the C20 has a 200 lb. heavier GVWR, its payload is actually 83 lbs. less than the Big 10’s! Of course, this is because the C20’s chassis is heavier by 283 lbs. But the parts that account for that extra weight offer significant benefits- -despite the Big 10’s slight advantage in ultimate payload capability, the C20’s stronger frame, full floating axle, and other more robust components suggest superior long term durability, particularly under near-maximum load conditions.

Moving beyond the 1975 numbers:

It is important to realize that the numbers I have selected above apply directly to 1975 model year vehicles. That said, most of this information is applicable with only minor adjustment to C10’s, Big 10’s and C20’s produced through the end of the 1980 model year. In fact, the most significant deviation occurred in the C20 line for the 1980 model year, when the 8,200 lb. GVWR was replaced by an 8,600 lb. option under the C6P option code. Since the “light duty/heavy duty” emission division point had been repositioned from 6,000 lbs. GVW to 8,500 lbs. GVW by start of the 1979 model year (1978 in California), the new for ’80 C6P option again allowed buyers to use leaded gasoline in a three quarter ton truck. Of course, the 1979 and 1980 Big 10’s were equipped with the full complement of light duty emission controls.

This above discussion should also be helpful in contemplating the relative abilities of half tons and three quarter tons offered during the 1981 to 1987 model years although there was some minor reshuffling of GVW packaging. Having lost its “non-smog control” appeal, the Big 10 package was no longer separately marketed from the lighter C10 models after 1980, although a maximum GVWR option of 6,100 lbs. was offered for C10’s from 1981 to 1987. Beyond this, some significant component changes occurred in the C20 lineup, such as the adoption of a semi floating axle for the first time in all three quarter tons (except those equipped with the 454 engine). Those changes might merit consideration in selecting one of the later models for your needs. But it is getting late, and that is beyond the scope of what I hoped to accomplish here.

Good luck as you consider your needs and choices!

Ken Lewis
Owner of a 1979 Chevy Big 10
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Old 05-12-2005, 11:41 AM   #5
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Quote:
Originally Posted by 80BIG10
I found the write up as posted by KIILEW:
WOW! Thanks for reposting that. Very informative. My '77 Silverado is one of the 6050lbs GVW 1/2 tons with practically zero emmission control equipment.
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Old 03-29-2014, 12:33 AM   #6
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Re: What is a Big 10 or Heavy half?

So, how do I tell if mine is the 6,050 or the 6,200? All I can see on the title is that the 4th digit is 4.
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Old 03-29-2014, 01:51 PM   #7
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Re: What is a Big 10 or Heavy half?

Wow. That guy was right - brevity is not his strong suit. And I'm grateful.

BadAz - do you still have your SPID label? There are RPOs associated with the various GVWs and it will likely appear on the SPID.

The second option, which we have not yet discussed, is that for $50 you can send your VIN to the GM Heritage Center and they will give you the original invoice for your specific truck. This will include all option content and pricing that your truck came with.

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Old 03-29-2014, 02:10 PM   #8
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Re: What is a Big 10 or Heavy half?

Quote:
Originally Posted by Keith Seymore View Post
Wow. That guy was right - brevity is not his strong suit. And I'm grateful.

BadAz - do you still have your SPID label? There are RPOs associated with the various GVWs and it will likely appear on the SPID.

The second option, which we have not yet discussed, is that for $50 you can send your VIN to the GM Heritage Center and they will give you the original invoice for your specific truck. This will include all option content and pricing that your truck came with.

K
I don't know what an SPID label is or where to find it if I did have one. Help?
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Old 03-29-2014, 04:43 PM   #9
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Re: What is a Big 10 or Heavy half?

The SPID is the "Service Parts Identification" sheet. It lists your truck's VIN, wheelbase, and then a list of all of the options your truck received from the factory.

I've seen reports from various owners of 73-87 trucks that their SPID's are located in one of two places:

A sticker inside the glovebox door.
A sticker on the driver's side inner fender in the engine bay.

For example, my 1984 has it's SPID on the driver's side inner fender.

If you find it, look at the list of options, and they will have codes with letters and numbers. These are RPO (Regular Production Option) codes. It is possible to find a list of each of these codes online, as they apply to your truck.
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Old 03-29-2014, 04:48 PM   #10
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Re: What is a Big 10 or Heavy half?

Quote:
Originally Posted by thefraze_1020 View Post
The SPID is the "Service Parts Identification" sheet. It lists your truck's VIN, wheelbase, and then a list of all of the options your truck received from the factory.

I've seen reports from various owners of 73-87 trucks that their SPID's are located in one of two places:

A sticker inside the glovebox door.
A sticker on the driver's side inner fender in the engine bay.

For example, my 1984 has it's SPID on the driver's side inner fender.

If you find it, look at the list of options, and they will have codes with letters and numbers. These are RPO (Regular Production Option) codes. It is possible to find a list of each of these codes online, as they apply to your truck.
Cool. I'm actually going to go pick the truck up next week, I'll check it out and see if it's still there. Thank ou.
Do you have the website where I can get another one if it's missing?
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Old 03-29-2014, 04:51 PM   #11
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Re: What is a Big 10 or Heavy half?

Check this link out:

http://www.outintheshop.com/

He makes reproduction 67-72 SPID's, however you want. I'm not sure if he makes 73-87 SPID's though.
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Old 03-29-2014, 05:11 PM   #12
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Re: What is a Big 10 or Heavy half?

Quote:
Originally Posted by thefraze_1020 View Post
Check this link out:

http://www.outintheshop.com/

He makes reproduction 67-72 SPID's, however you want. I'm not sure if he makes 73-87 SPID's though.
Nope. Just 67-72. I wonder how he looks it all up for each truck. I would imagine the combinations are endless.
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Old 03-29-2014, 05:22 PM   #13
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Re: What is a Big 10 or Heavy half?

Well then if he only does 67-72, I need to find someone who will do 73-87 SPID's, because mine is trashed and needs to be reproduced.
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Old 03-31-2014, 11:40 AM   #14
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Re: What is a Big 10 or Heavy half?

You guys are mixing metaphors a bit.

Re: getting SPID labels made - I believe chipflyer will make a SPID for whatever model year truck you want. The trick is that YOU have to tell him what RPOs you want on the label.

Re: what RPOs you want on the label: you are correct - the possibilities are endless.

For 1976 and newer you can send your VIN and $50 to the GM Heritage Center archive and they will give you the actual invoice for your specific truck. This will include all RPOs and the pricing for those. Link: http://www.gmmediaarchive.com/

If that does not work for you then your only other hope is to find an original build sheet in the truck somewhere (under the carpet, stuck in the seat springs, above the headliner, etc). These were to help faciliate the build and exist only in the truck (there were intended to be thrown away at the completion of the build and no copies were kept by General Motors).

If that doesn't work then you'll just have to use your imagination and make something up...



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Old 03-31-2014, 04:04 PM   #15
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Re: What is a Big 10 or Heavy half?

I have a '78 Big 10.

It has the 6200lb GVWR.

What I'm curious about, could the Big 10 package be added to a short box 4x4??? That's what my truck is. It has a 12 bolt 6 lug rear axle and a Dana 44 up front. Also has the 2-stage rear springs.

Im curious about this because I have not seen or heard of any 4x4 Big 10's, let alone with short boxes.
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Old 03-31-2014, 07:39 PM   #16
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Re: What is a Big 10 or Heavy half?

Quote:
Originally Posted by RIDE-RED 350r View Post
What I'm curious about, could the Big 10 package be added to a short box 4x4??? ..... Im curious about this because I have not seen or heard of any 4x4 Big 10's.
No, I don't think the "Big 10" or "Heavy Half" was available for 4x4 trucks.

According to the info kits from http://gmheritagecenter.com/gm-herit...tion-kits.html, the RPO F44 "Big 10" is only listed for C10 2 wheel drive trucks. And according to the GVWR selector tables in those kits, the GVWR on all 1976 through 1980 K10 (1/2 ton 4x4) trucks is 6200 lbs.

As was mentioned earlier, the whole idea of the Big 10 was to bump the GVWR up above the 6000 lbs. threshold. That allowed buyers to purchase a 1/2 ton truck that didn't require catalytic converters & other emissions equipment that was required on lighter trucks. But since the 1/2 ton 4x4 trucks were already above that threshold, there wasn't any need to raise the GVWR any higher.
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Old 03-31-2014, 08:00 PM   #17
RIDE-RED 350r
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Re: What is a Big 10 or Heavy half?

OK, thank you for clearing that up.

But here is the kicker, my VIN indicates the f44 package.

Also have the non-cat crossmember..but as you explained could be due to the std K-10 being above the 6,000lb threshold as-is....

Granted, I could have a K-10 that had a Big-10 cab transplanted onto it.

And then there is the rear springs and the 12 bolt/6 lug axle found on the Big 10 package... or so I tend to think from what I have been able to learn...

Pics below are of my rear springs... I don't think this is a std K-10 rear spring, or is it??

Is it possible this truck was special ordered with the Big-10 package??

I think I may be more confused now.. LOL!
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Old 03-31-2014, 08:13 PM   #18
RIDE-RED 350r
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Re: What is a Big 10 or Heavy half?

OK, just checking out that page you linked, (very cool by the way!) it seems the dual stage springs were standard on K-10's. SO that questions is answered...

Looking like a Big 10 cab was transplanted onto my chassis.
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Old 03-31-2014, 08:31 PM   #19
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Re: What is a Big 10 or Heavy half?

Quote:
Originally Posted by RIDE-RED 350r View Post
OK, thank you for clearing that up.

But here is the kicker, my VIN indicates the f44 package.

Granted, I could have a K-10 that had a Big-10 cab transplanted onto it.
When you say the VIN indicates the F44 package, I assume you mean the 4th character is a "4", correct? Is the 2nd character a "C" or a "K"?

If the 2nd character is a "C" then it's likely a cab swap that utilized a Big-10 cab. But if it's a "K" then that would indicate a factory 4x4 VIN.

I know the RPO F44 was used to designate the "heavy duty chassis" option for a number of years ... not just the "Big 10" & "Heavy Half" during this time period. So it might have been possible to order F44 on a 4x4 as well ... I didn't see it listed anywhere aside from the C10 listings in those info kits but I might have overlooked it.
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Old 03-31-2014, 09:11 PM   #20
RIDE-RED 350r
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Re: What is a Big 10 or Heavy half?

OK you are spot on, I don't have a Big 10 and I now realize where I have made my mistake... Looking at the LMC VIN decoder, I was mixed up on the graph.

My VIN is CKL14... So that's C-Chevy, K-4wd, L-350-4, 1-10, 4-Pickup.........

Thank you for helping me figure this out and ultimately figure out I was misreading the VIN decoder.

After looking more at that PDF, I figured out all K-10's got the dual stage rear springs in '78. I just happened to get lucky with the 12 bolt rear and Dana 44 front with 3.73 gears??

Last edited by RIDE-RED 350r; 03-31-2014 at 09:20 PM.
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