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Old 06-04-2006, 10:55 PM   #1
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Origin of the "Heavy" Half-Ton?

What is this? 1/2 ton with overloads? I have never seen "Heavy Half Ton" listed as an option or even advertised for that matter but the term keeps coming up in private advertisements. Someone asked me and I had to speculate. Anyone have the real story?
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Old 06-04-2006, 10:58 PM   #2
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Re: Origin of the "Heavy" Half-Ton?

Never an option on the 67 - 72... just ppl confused when they see 6 lugs or helper springs.
This was in fact a thing on the 73 - 87... somewhere in the late 70's early 80's they did it. I think it was mostly a bogus thing... it's not like it was a real HD thing... it still had 5 lug wheels, and girly springs.
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Old 06-04-2006, 11:15 PM   #3
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Re: Origin of the "Heavy" Half-Ton?

The Heavy Half was basically a 5/8's ton rear leafs. No over loads or anything like that. Just rear leafs between the 1/2 and 3/4.
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Old 06-05-2006, 01:18 AM   #4
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Re: Origin of the "Heavy" Half-Ton?

So was it an actual, legitimate option?
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Old 06-05-2006, 03:40 AM   #5
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Re: Origin of the "Heavy" Half-Ton?

The Chevy 'Big 10', GMC 'Heavy Half', Dodge D-150 and Ford F-150 all came out about 1976. At the time, catalytic converters were required on all trucks under 6000lbs. GVW.. These heavy duty half tons all had GVW's of 6010-6100lbs., and didn't need catalytic converters. They also still offered big blocks and 4 speeds in many instances.
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Old 06-05-2006, 06:00 AM   #6
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Re: Origin of the "Heavy" Half-Ton?

per '71 TruckService manual...RPO G50 increased rear axle capacity from 2500 to 3221 lbs. RPO G50 also included H78-15B upgrade from G78-15B tires.
(RPO = Regular Production Option; if I recall correctly )
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Old 06-05-2006, 07:23 AM   #7
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Re: Origin of the "Heavy" Half-Ton?

My dad was a state inspector and a mechanic for more than 45 yrs he knew the specs and the laws. So when he traded in his 72 step 402/400/411 posi (never should have gotten rid of it.) He ordered and still has a 76 step side 454/400/411 with rear leafs that look like a 3/4 no emissions required thats why he did
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Old 06-05-2006, 07:30 AM   #8
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Re: Origin of the "Heavy" Half-Ton?

Quote:
Originally Posted by GMC Jim
per '71 TruckService manual...RPO G50 increased rear axle capacity from 2500 to 3221 lbs. RPO G50 also included H78-15B upgrade from G78-15B tires.
(RPO = Regular Production Option; if I recall correctly )
Yup,there were heavier suspension options.Just no Heavy Half designation whatsoever.It`s just a case of something coming along later,then people looking back inaccurately.BobB nailed it.It was an emmissions thing.Catilytic Cans started in`75 on cars and under 7,000# trucks.The last of the OBS diesel Suburban 8-luggerss were badged 1500,some kinda emmission/weight class game.
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Old 06-05-2006, 07:16 PM   #9
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Re: Origin of the "Heavy" Half-Ton?

On the 73-87's a Heavy Half was a Half Ton pickup that the rear "HALF" was a 3/4 T spring. It increased the rear capacity enough to allow them to get out of emission testing. It was also called a Big 10.
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Old 06-05-2006, 10:33 PM   #10
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Re: Origin of the "Heavy" Half-Ton?

Thanks...I knew the someone would eventually separate the wheat from the chaff. Thanks guys...I will pass this information on...gotta love the info on this board.
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Old 06-06-2006, 08:51 AM   #11
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Re: Origin of the "Heavy" Half-Ton?

BTW,they never made a Halfhorn from the factory.
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Old 06-11-2006, 12:40 AM   #12
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Re: Origin of the "Heavy" Half-Ton?

FWIW, I am looking at 2 manuals here. Both list that you could get a Dana 60 in a half-ton.

Manual #1 is manual number XR60-GM, "Model-60 GMC/Chevrolet 1967-1978, Spicer Axles/Rear" by the Dana Corporation.
This lists all the Bill of Material Numbers, part numbers etc. etc.
It lists that the Dana 60 was installed/available on C-10's in the years of 1968,1969,1970 and on K-10's in the year 1967.

Manual #2 is manual number X-172001 GMC Trucks Master Parts Book Models 1500,2500,3500 (for 1972).
In the Model line up, it lists a "Spicer SS 60-35" as an optional rear axle for certain models 67-70 (but doesn't list it for the 67 K10 as the Dana manual does).

From the 72 GMC parts manual, it looks like the Dana 60-35 is a six bolt axle flange where as a regular Dana 60 is an eight bolt axle flange.

So, if you had a Dana 60 in a half-ton in 1967-1970, I don't know what they called it, technically, and agree that the "heavy half" nomenclature is carry over from they 1973+ years.

Confusion abounds in that when people say "heavy half" they may not be referring about the "leagality" of the name but what it represents -- a half ton with a three-quarter ton axle/running gear under it. Did or did not GM ship out the door a half-ton with a three-quarter ton rear in it?

According the manuals and peoples recollections (including mine, but I thought I saw 8 bolt hubs on the few I've "seen"), I think they did. I am not a Dana expert so I can't tell you exactly what a Dana 60-35 is other than it is a Dana 60 of some sort.

Just my 2 cents and I may be wrong on my "recollections".
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Old 10-24-2016, 04:54 PM   #13
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Re: Origin of the "Heavy" Half-Ton?

I happen to have inherited by marriage a "Heavy" Half-Ton.
This beautiful 1972 Chevy Truck
(K20-Heavy Half, Short-box, Fleet side, with every bell and whistle you could order) will be in our will.
In the late 1990's my husband and I set out to restore this beautiful family heirloom. In trying to keep it as close to original we discovered several things. First off in the springs on the back of the seat was the original dealer speck sheet. Yes I have titled it correctly by calling it a "Heavy Half".

Here is a few more facts we we learned:
1. The 1972 is slightly different than all other years of the Chevy Truck. There are a few "flags" that can help you tell the difference. If anyone wants to know I'll be glad to share.
2. The "Heavy" half was a designation that was also a lot of times labeled as the Custom Camper. This let repair garages, auto-body shops, parts houses etc know that although the outer body, eng. etc was the K20 the frame rail, rear "pumpkin", driveline, and rear axel, springs, brakes etc. were beefier. They were what today would be called a 3/4 ton because in 1972 there was not a K30 available.
3. The K designates a 4x4 and the C disignates a 2x2.
4. The "Longhorn" or longbox was not available in the K20.
5. That bumpers on the Cheyene package with all the bells and whistles you could have, were more often than not added at the dealership. So when you ordered a custom truck you truly got a "Custom" one of a kind truck.
6. That according to the archive department at Chevy that I talked to - of the 6,000 frames made under this distinction of K20 "Heavy Half", They were allotted for the Truck both step & fleet side, Van and Blazer. If split even between the 4 that makes our beastie a very, very rare truck.
7. That if you want to get these beautiful trucks appraised or insured properly it is a tough job!

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Old 10-24-2016, 05:02 PM   #14
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Re: Origin of the "Heavy" Half-Ton?

A 1972 K20 is a 3/4 ton 4 wheel drive truck...not a "heavy half"

Your truck sounds very nice, post a pic when you can!
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Old 10-24-2016, 05:18 PM   #15
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Re: Origin of the "Heavy" Half-Ton?

To my recollection, the highest GVW rating you could get on our trucks was 5400lb rating on the GVWR plate.
As mentioned they upped this starting in 1973 and if you get a chance to look at the rear spring pack on a mid 70's heavy half/Big 10....it is very substantial....way more than the 67-72' group.
The other thing I believe the option called up was bigger (wider) brakes which were needed.
I've seen a lot of these 'heavy half's' carrying campers and when equipped with 16" tires...they seem to have no problems whatsoever carrying a pretty heavy load, particularly if you add on the Auxiliary/Overload spring system on top of that already substantial group of Heavy Half' springs.

Now, that said...it is not uncommon to see 67-72's (or even the next earliest series 64/65/66') running around with a designation on the front lower side of the box saying 6000 GVW...which I find interesting.
I have seen this hundreds of times on older trucks.....who made that call?... and wrote/stamped that writing on the side of the box?....it wasn't the owners.
Interesting stuff.
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Old 10-24-2016, 06:04 PM   #16
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Re: Origin of the "Heavy" Half-Ton?

Check the VIN number and your original spec sheet if you can. Each truck has all the information listed on this to give you information. My research took me very deep in to "my chevy" and of course it has even more sentimental value so I went into extensive detail. Including that call I made to the Chevy factory's archive department.
I check out various websites including this forum on a regular basis although I don't usually get involved or comment. Here are some of the ones I follow:
1.. http://www.fourwheeler.com/features/...kward-glances/
2. https://www.brotherstrucks.com/
3.https://www.tuckersparts.com/home.php
4. http://www.classicparts.com/
5.http://www.oldchevytrucks.com/
http://www.vintagechevytrucks.com/

I didn't mean to start a controversy. It is just interesting to walk through a "classic car show" and see the various trucks passed off for what they are and in all reality aren't and I just usually shake my head and walk on.

We all own an awesome piece of American Cultural History and when all comes down to it...

It's a Classic Chevy and our PRIDE and JOY!

Sorry I only have pictures from older than 2007 - but they are attached!
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Old 10-24-2016, 08:23 PM   #17
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Re: Origin of the "Heavy" Half-Ton?

Quote:
Originally Posted by heligypsy View Post
I happen to have inherited by marriage a "Heavy" Half-Ton.
This beautiful 1972 Chevy Truck
(K20-Heavy Half, Short-box, Fleet side, with every bell and whistle you could order) will be in our will.
In the late 1990's my husband and I set out to restore this beautiful family heirloom. In trying to keep it as close to original we discovered several things. First off in the springs on the back of the seat was the original dealer speck sheet. Yes I have titled it correctly by calling it a "Heavy Half".

Here is a few more facts we we learned:
1. The 1972 is slightly different than all other years of the Chevy Truck. There are a few "flags" that can help you tell the difference. If anyone wants to know I'll be glad to share.
2. The "Heavy" half was a designation that was also a lot of times labeled as the Custom Camper. This let repair garages, auto-body shops, parts houses etc know that although the outer body, eng. etc was the K20 the frame rail, rear "pumpkin", driveline, and rear axel, springs, brakes etc. were beefier. They were what today would be called a 3/4 ton because in 1972 there was not a K30 available.
3. The K designates a 4x4 and the C disignates a 2x2.
4. The "Longhorn" or longbox was not available in the K20.
5. That bumpers on the Cheyene package with all the bells and whistles you could have, were more often than not added at the dealership. So when you ordered a custom truck you truly got a "Custom" one of a kind truck.
6. That according to the archive department at Chevy that I talked to - of the 6,000 frames made under this distinction of K20 "Heavy Half", They were allotted for the Truck both step & fleet side, Van and Blazer. If split even between the 4 that makes our beastie a very, very rare truck.
7. That if you want to get these beautiful trucks appraised or insured properly it is a tough job!

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Welcome heligypsy, nice truck you have there. Research aside, just to be clear, the Custom Camper is not a "Heavy Half". It's a Z81 option checked off by the original buyer that gave him or her a nameplate that said "Custom Camper" - the format took different forms in 65, 66-68, 69-71, and finally, 72. As Tim pointed out above, one could order heavier option rear axles, or leafs vs coils, (and even helper springs), Custom Camper or not. Note that coils or leafs could be had on 1/2 or 3/4 ton truck. Custom Camper could be had in 1/2 or 3/4 or 1 tons (C only for the 1 ton). Some heavy duty options needed to be selected before the Z81 option was, well, an "option" available to a buyer. A K20 is a 3/4 ton 4x4. There were no 3/4 ton 115" wb trucks, in C or K form. Titling isn't really relevant, the average DMV clerk doesn't know a Datsun from a Dachshund. Just trying to keep the gouge we spread here straight for those that read it in the future - owning a heavy duty C or K10 is not the same as owning a "Heavy Half" - a term that was not coined officially by GM until '76.

If you've got any current pics, especially of the SPID, we'd love to see em! Great looking truck in one of my favorite colors.

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Old 10-24-2016, 09:49 PM   #18
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Re: Origin of the "Heavy" Half-Ton?

After '69 there were no Custom Camper/10s made. A K/20 is a 3/4 ton 4wd. They are all heavier than 1/2s, which were K/10s. Same is true in C-series. Check around the site. It''s been around for quite few years and we've been working this stuff out all along. It's not that there is never anything new to learn, happens every day, but this isn't the place to come to pull up old threads and present info as if no one here has ever looked into it or worked it through over and over again. This thread was started questioning whether there was any such thing as a "Heavy Half" in these trucks and the answer is no. One half ton could have a heavier GVW than another, but it was never a package or model with a specific designation.
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Old 10-25-2016, 08:27 PM   #19
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Re: Origin of the "Heavy" Half-Ton?

Quote:
Originally Posted by heligypsy View Post
I happen to have inherited by marriage a ... beautiful 1972 Chevy Truck...
Welcome to the board! Sadly there isn't much of your posts I can agree with. Hopefuly it is a contextual issue more than anything else.

Fleetside pickup beds (67-72) were offered in three lengths.

The "shortbed", a nominal 6-1/2' (78") was offered on 115" wb C-10 and K-10s.

The "longbed", a nominal 8' (98") was offered on 127" wb C-10, K-10, C-20 and K-20s.

The "Longhorn", a nominal 8-1/2' (104") was offered on 133" wb C-20 and C-30s. Of note the C-20 Longhorn used the heaver and longer wheelbase C-30 frame with basically a C-20 leaf suspension.
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Old 10-25-2016, 08:56 PM   #20
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Re: Origin of the "Heavy" Half-Ton?

Quote:
Originally Posted by Coley View Post
To my recollection, the highest GVW rating you could get on our trucks was 5400lb rating on the GVWR plate.
Actually 5400lb is only the highest GVW rating for a C/10 pickup.
K/10 pickups went all the way to 6000.

Blazers, C/10 5400lb and K/10 5850lb

Suburbans with all three seat rows could go even higher, C/10 6650lb and K/10 6800lb.



Quote:
Originally Posted by Coley View Post
...Now, that said...it is not uncommon to see 67-72's (or even the next earliest series 64/65/66') running around with a designation on the front lower side of the box saying 6000 GVW...which I find interesting.
I have seen this hundreds of times on older trucks.....who made that call?... and wrote/stamped that writing on the side of the box?....it wasn't the owners.
Interesting stuff.
All Good
Coley
It used to be a common requirement by states to post a maximum GVW class on a pickup since it was considered a commercial vehicle. 6000lb was a common point and you will see many trucks with 6000lb GVW and an "Under" or "Max" prefix. However, often just the weight limit was applied.

Most of the time they were applied at the dealer, being bread and butter for many a local budding sign painter. Decals are also seen from really nice plates and banners to individual letters/numerials. Even mailbox letters can be seen on occasion.
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Old 10-26-2016, 02:58 PM   #21
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Re: Origin of the "Heavy" Half-Ton?

Quote:
Originally Posted by leddzepp View Post
A 1972 K20 is a 3/4 ton 4 wheel drive truck...not a "heavy half"
Nor will it be a short wheel base. The wheel base of the truck would be 127". That truck should be titled as a 3/4 ton.
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Old 10-29-2016, 12:36 PM   #22
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Re: Origin of the "Heavy" Half-Ton?

When I think "heavy 1/2 Ton" , I envision a C 10 ordered with heavy duty springs, 4 speed trans, 292 big six and lock ring wheels, the way it was none in the 60's. Then in the mid 70's, the BIG 10 package came along with a higher GVW, mainly to get away from emission requirements which 3/4 ton were exempt from. But the K 10 is a slighty different animal in the 1/2 ton world, it has the same frame ( section modulus) as a K 20 3/4 ton in the '67-'72 era. I believe this is what heligyspy was referring to.
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Old 10-29-2016, 02:39 PM   #23
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Re: Origin of the "Heavy" Half-Ton?

Quote:
Originally Posted by factorystock View Post
When I think "heavy 1/2 Ton" , I envision a C 10 ordered with heavy duty springs, 4 speed trans, 292 big six and lock ring wheels, the way it was none in the 60's. Then in the mid 70's, the BIG 10 package came along with a higher GVW, mainly to get away from emission requirements which 3/4 ton were exempt from. But the K 10 is a slighty different animal in the 1/2 ton world, it has the same frame ( section modulus) as a K 20 3/4 ton in the '67-'72 era. I believe this is what heligyspy was referring to.
Just to set the record straight on 4x4 frames: K/10 Long bed and K/20 share the same frame. Short bed K/10 and K/5 are different frames from each other and obviously the long bed trucks. The short K/10 and K/5 both are lighter duty than the long bed K frame.
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Old 10-29-2016, 03:05 PM   #24
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Re: Origin of the "Heavy" Half-Ton?

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Originally Posted by 57taskforce View Post
Just to set the record straight on 4x4 frames: K/10 Long bed and K/20 share the same frame. Short bed K/10 and K/5 are different frames from each other and obviously the long bed trucks. The short K/10 and K/5 both are lighter duty than the long bed K frame.
Agree and in fact the 4x2 C10-20 have slightly stiffer frames than the 4x4 K10-20.

The frame section and modulus numbers, 39k psi carbon steel through C30s. Note the increased section height, flange width and thickness changes of the frame as the series step up.

C Blazer
C10 115"
C10 127"- 6.04" section height, 2.53" flange width, 0.156" thick, 2.98 section modulus

C20 127"- 6.11" section height, 2.46" flange width, 0.194" thick, 3.71 section modulus

C20/30 133" (Longhorns)- 7.20" section height, 2.77" flange width, 0.194" thick, 5.05 section modulus

K Blazer
K10 115"- 6.02" section height, 2.71" flange width, 0.141" thick, 2.70 section modulus

K10 127"
K20 127"- 6.09" section height, 2.75" flange width, 0.186" thick, 3.48 section modulus

Referenced from the GM 1970 truck engineering specifications book.
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Old 10-30-2016, 01:12 PM   #25
slider701
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Re: Origin of the "Heavy" Half-Ton?

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You could get C10 with short bed with Dana 60 rear end. It was part of Max Traction package.

This is the Dana 60 under my dad's truck
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