The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1967 - 1972 Chevrolet & GMC Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 02-07-2019, 02:36 PM   #1
72kool
Registered User
 
72kool's Avatar
 
Join Date: Dec 2012
Location: kearney nebraska
Posts: 576
How strong is the frame?

Ok so in my journey to make my truck my permanent daily, I'm looking into my towing needs. I came across this thread about a 4x4 swap http://67-72chevytrucks.com/vboard/s...d.php?t=659340

My understanding is that the C20 frame is stronger than a k20 frame? Someone posted a lot of specs from a manual and it says the C20 is 32% (I can't remember exact number) stronger than the k20. Is that correct, Or am I reading it wrong??

Reason I'm looking it up is I am looking into a gooseneck hitch, which will be challenging with the coil springs. But first I am looking into the strength of the frame. I see gooseneck and 5th wheels pulled with k20s on here alot but never a C20. Any insight would be appreciated
__________________
1972 GMC C20 Custom Camper 350/TH350
72kool is offline   Reply With Quote
Old 02-07-2019, 03:19 PM   #2
Coley
Senior Member
 
Coley's Avatar
 
Join Date: Oct 2011
Location: Victoria, B.C
Posts: 3,665
Re: How strong is the frame?

What are your towing needs?
-type of load?
-Max Weight?
-Towing Conditions? (mountains? long distance? city? ??)

...you don't need to swap frames in order to improve the trucks capability but remember, it won't change the tow capacity from a legal standpoint.

All good
Coley
__________________
....for some men, there is experience, skill and effort....for the others...there is visa and UPS LOL
1966 Chevy 1/2 ton (Florida- Red/white)
1972 Chevy 1/2 ton (California- Blue/white)
2005 Chevy Silverado HD2500/Duramax
2000 Dodge Ram 1500
Coley is offline   Reply With Quote
Old 02-07-2019, 03:22 PM   #3
kwmech
Senior Member
 
Join Date: Mar 2003
Location: Colfax-California
Posts: 5,416
Re: How strong is the frame?

Not hard to get rid of the coils and convert to leaf
kwmech is offline   Reply With Quote
Old 02-07-2019, 05:46 PM   #4
72kool
Registered User
 
72kool's Avatar
 
Join Date: Dec 2012
Location: kearney nebraska
Posts: 576
Re: How strong is the frame?

I'm not looking at swapping frames per say. I am looking into installing a gooseneck hitch. I can't find anywhere that somebody has a gooseneck on a C20. Only the k20 trucks. But I found that post that said C20 are stronger so I was curious if that was true. I will probably have to build my own hitch no matter what.

My towing needs are a two car gooseneck flatbed. It will be hauling Derby cars all over the state. I have a bumper pull single car trailer now. I know the truck can do it, i have pulled heavy loads before with it, just trying to figure out how to make a hitch for this truck. I have all the brakes updated, have the disc up front and it will have trailer brakes soon. Not worried about the capacity of towing, worried about how to get a gooseneck hitch installed that won't come off and kill someone.
__________________
1972 GMC C20 Custom Camper 350/TH350
72kool is offline   Reply With Quote
Old 02-07-2019, 06:05 PM   #5
B. W.
Senior Member
 
B. W.'s Avatar
 
Join Date: Nov 2014
Location: Bigfork, Montana
Posts: 1,061
Re: How strong is the frame?

Back in the '80's I towed a gooseneck trailer all over Colorado with a '69 GMC C25. Had a BB, T400 & drum brakes. It went up the passes too slow & came down too Fast! All in all, it did a fine job & never talked back.
B. W. is offline   Reply With Quote
Old 02-07-2019, 06:07 PM   #6
72kool
Registered User
 
72kool's Avatar
 
Join Date: Dec 2012
Location: kearney nebraska
Posts: 576
Re: How strong is the frame?

Fortunately I don't really have much for big inclines around here. Mostly flats with small hills. What hitch did you have? Any ideas on what to do for a hitch?
__________________
1972 GMC C20 Custom Camper 350/TH350
72kool is offline   Reply With Quote
Old 02-07-2019, 08:21 PM   #7
special-K
Special Order

 
special-K's Avatar
 
Join Date: Nov 2004
Location: Mt.Airy,MD
Posts: 67,875
Re: How strong is the frame?

Show us that thyread. I never heard of C/20 frames being stronger than K/20. Why would GM do that? Maybe it was a C/20 Longhorn which sits on a 1t frame. Makes no sense at all for C/20 to be 1/3 stronger than K/20 which would be used in more harsh conditions. If you believe this is true, then why are you concerned?
__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed"

'67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi...'The 67' (project)
'72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok...'The 72'
Tim

"Don't call me a redneck. I'm a rough cut country gentleman"

R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586
special-K is online now   Reply With Quote
Old 02-07-2019, 08:54 PM   #8
72kool
Registered User
 
72kool's Avatar
 
Join Date: Dec 2012
Location: kearney nebraska
Posts: 576
Re: How strong is the frame?

The link is in the original post at the top. It says that according to the 1970 GM manual of engineering, that a C20 is 8% stiffer frame than a k20. I found that interesting.
Where it applies to me, I always saw large trailers being pulled by k20 trucks. I have never seen on this forum or web, a C20 pulling a 32' gooseneck. I started to wonder if it was because the frame was too weak. But according to the link provided above, my frame is stronger. My question in all of this was, is that statement true? Any reason not to pull. Gooseneck with a C20 coil spring truck? I've seen some c30 trucks , but hey, they are one tons so nobody thinks twice if it will handle it
__________________
1972 GMC C20 Custom Camper 350/TH350
72kool is offline   Reply With Quote
Old 02-07-2019, 08:54 PM   #9
Mike C
Registered User
 
Mike C's Avatar
 
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 6,926
Re: How strong is the frame?

Frame strength doesn't have a whole lot to do with it IMO. Assuming 10% pin weight and 10,000 GVWR trailer you are only looking at 1000# in the bed.

What you should REALLY be worried about are brakes, cooling, transmission and tires.

And if you are looking at hauling more than 10,000# around all the time you should consider more truck.
__________________
44 Willys MB
52 M38A1
64 Corvette Coupe
68 Camaro 'vert LT1 & TH700
69 Z/28 355 12.6's @110
69 Chevy Short Step 4 1/2"/7" drop
72 Jimmy 4WD 4spd 4" & 35's
02 GMC 2500HD 4x4 Duramax
Mike C is online now   Reply With Quote
Old 02-07-2019, 09:37 PM   #10
72kool
Registered User
 
72kool's Avatar
 
Join Date: Dec 2012
Location: kearney nebraska
Posts: 576
Re: How strong is the frame?

Cooling is taken care of. It's all new system and has never had an issue overheating. If it gets warm while towing the bigger trailer, I'll upgrade to bigger radiator and electric fans. The transmission is decent, but will be changed also. Looking to do either a built 700r4 or possibly a 4l80e . Though a built 700r4 should be enough
__________________
1972 GMC C20 Custom Camper 350/TH350
72kool is offline   Reply With Quote
Old 02-07-2019, 10:20 PM   #11
kwmech
Senior Member
 
Join Date: Mar 2003
Location: Colfax-California
Posts: 5,416
Re: How strong is the frame?

Quote:
Originally Posted by 72kool View Post
Cooling is taken care of. It's all new system and has never had an issue overheating. If it gets warm while towing the bigger trailer, I'll upgrade to bigger radiator and electric fans. The transmission is decent, but will be changed also. Looking to do either a built 700r4 or possibly a 4l80e . Though a built 700r4 should be enough
Just build a 4L80 for the towing. 700 won't last no matter how much money you put into it trying to make it as strong as a stock 4L80. Towing a gooseneck with 2 cars on it with a 700 is...well....
kwmech is offline   Reply With Quote
Old 02-07-2019, 10:47 PM   #12
B. W.
Senior Member
 
B. W.'s Avatar
 
Join Date: Nov 2014
Location: Bigfork, Montana
Posts: 1,061
Re: How strong is the frame?

Quote:
Originally Posted by 72kool View Post
Fortunately I don't really have much for big inclines around here. Mostly flats with small hills. What hitch did you have? Any ideas on what to do for a hitch?
I don't remember, it was a fifth wheel type that sat in a cradle between two A frame uprights.
B. W. is offline   Reply With Quote
Old 02-08-2019, 02:47 AM   #13
jeffahart
Senior Member
 
jeffahart's Avatar
 
Join Date: May 2012
Location: Los Angeles, CA
Posts: 1,460
Re: How strong is the frame?

My insight is stolen from SS Tim post #20 in the following thread. It does seem that they build some flexibility into the K series for offroad flexibility, but you really need to look at the payload ratings. I would be more concerned with offroad tires than a K frame. Check out Tims numbers, they are interesting and a good reference.

http://67-72chevytrucks.com/vboard/s...d.php?t=463016


j
__________________
White K20
jeffahart is offline   Reply With Quote
Old 02-08-2019, 04:37 AM   #14
toolboxchev
Registered User
 
Join Date: Jul 2015
Location: 2nd left past the stump on a dirt road.
Posts: 1,619
Re: How strong is the frame?

I can tell you this, Standard C20 Longbed, leaf spring dana rear end will do a wet cord of oak no problem.

Doug Fir mostly seasoned I believe comes in at roughly 3,300 lbs.

Oak is considerably more.

I quickly added a set of HellWig Adjustable Progessive springs to the rears and never had an issue with a Cord 1/4 after that.

Original Drums (rebuilt) would stop me coming down the mountain. Oregon has some pretty big hills. Some fade but not smoking my foot on the pedal either.

Most people on here would agree the C20 frame looks much like a C10 frame. They are 2 completely different steels used in them.
toolboxchev is offline   Reply With Quote
Old 02-11-2019, 05:29 AM   #15
burnin oil
Registered User
 
Join Date: Jan 2013
Location: Eastern TN
Posts: 1,088
Re: How strong is the frame?

Quote:
Originally Posted by Mike C View Post
Frame strength doesn't have a whole lot to do with it IMO. Assuming 10% pin weight and 10,000 GVWR trailer you are only looking at 1000# in the bed.

What you should REALLY be worried about are brakes, cooling, transmission and tires.

And if you are looking at hauling more than 10,000# around all the time you should consider more truck.
10% is bumper pull. GN should be closer to 25%
burnin oil is offline   Reply With Quote
Old 02-11-2019, 09:02 AM   #16
Mike C
Registered User
 
Mike C's Avatar
 
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 6,926
Re: How strong is the frame?

Quote:
Originally Posted by burnin oil View Post
10% is bumper pull. GN should be closer to 25%
You are correct. 15%-25% Gooseneck pin weight on the truck.

But IMO, frame strength is the least important of all the things discussed in this thread concerning capability.

The first three are Brakes, brakes, brakes. Then tires. This is the safety aspect. Then follows cooling and transmission as they are durability items.
__________________
44 Willys MB
52 M38A1
64 Corvette Coupe
68 Camaro 'vert LT1 & TH700
69 Z/28 355 12.6's @110
69 Chevy Short Step 4 1/2"/7" drop
72 Jimmy 4WD 4spd 4" & 35's
02 GMC 2500HD 4x4 Duramax
Mike C is online now   Reply With Quote
Old 02-11-2019, 09:28 AM   #17
jbarron
Registered User
 
Join Date: Apr 2006
Location: Spring, Texas
Posts: 103
Re: How strong is the frame?

Both of my C20's have gooseneck hitches in them.
They are both leaf spring trucks.
I looked at a 3rd one with the exact same setup, but didn't buy it.
Come to think of it I have not seen a C20 without a gooseneck hitch.
__________________
'72 3/4 Cheyenne Super 402/TH400 Gear Vendors
'72 3/4 Cheyenne Super 350/200R4
'50 1/2 Chevy 3 Window
jbarron is offline   Reply With Quote
Old 02-11-2019, 11:23 AM   #18
davepl
Registered User
 
davepl's Avatar
 
Join Date: Aug 2006
Location: Redmond, WA
Posts: 6,240
Re: How strong is the frame?

FWIW, I have the Longhorn frame which is C30 except for C20 front suspension bits, but the full C30 rails. It still is only rated for 7500 I think, if that!
__________________
1970 GMC Sierra Grande Custom Camper - Built, not Bought
1969 Pontiac 2+2 427/390 4-speed Coupe
1969 Pontiac 2+2 427/390 4-speed Convertible
davepl is offline   Reply With Quote
Old 02-11-2019, 12:30 PM   #19
71blksuper4x4
SWB 4x4 Collector
 
71blksuper4x4's Avatar
 
Join Date: Jun 2001
Location: Osage City, KS
Posts: 4,799
Re: How strong is the frame?

The C30 cab n chassis frames are even thicker and taller rails than the square body K30 frames.
__________________
TREVOR
1970 CST swb 4x4 (speedwarning,cruise,tilt,tach,8track, original red shoulder belts,tow hooks)
1972 Jimmy (soon to be Hickey cloned)
1971 Cheyenne Super 4x4 swb (tilt,tach,buckets, original blue shoulder belts,am/fm,cruise,tow hooks, dealer 8 track)
1972 Cheyenne Super K20 4x4 Custom Camper (tilt, tach, am/fm, tow hooks, bed toolbox, aux gas tank
1972 Cheyenne Super Crew Cab K30 4x4 Duramax, Allison, np205, buckets, tow hooks (CURRENT PROJECT)
http://67-72chevytrucks.com/vboard/s...d.php?t=624819
1989 V3500 Crew Cab (454tbi, NV4500, np205)
1970 Chevelle SS (LS5 454,th400,8track,buckets,tach)
:2004 Jeep Wrangler Rubicon (daily driver)

WTB: 1968-70 Cruise Control Lever
71blksuper4x4 is offline   Reply With Quote
Old 02-11-2019, 03:12 PM   #20
67 chevelle
Senior Member
 
67 chevelle's Avatar
 
Join Date: May 2013
Location: WEST PALM FLORIDA
Posts: 1,153
Re: How strong is the frame?

forget the 700 POS , 4L80 all the way
__________________
68 Long Fleet , ly6 , turbo 350 , 3-5 drop , original paint , front discs
67 Small window , 7 foot bed , tweaked 6.0 LSX 2004R Medium Olive
58 Apache fleet , 235 , offy intake , dual exhaust , 4 on the floor , red/white
69 Long Fleet , Custom , 6.0, 4l60 , AC , Medium Olive
67 chevelle is online now   Reply With Quote
Old 02-11-2019, 07:22 PM   #21
Mike C
Registered User
 
Mike C's Avatar
 
Join Date: Dec 1999
Location: Austin, TX, USA
Posts: 6,926
Re: How strong is the frame?

Quote:
Originally Posted by davepl View Post
FWIW, I have the Longhorn frame which is C30 except for C20 front suspension bits, but the full C30 rails. It still is only rated for 7500 I think, if that!
My '70 C2500 Longhorn GMC parts truck was only rated at 6600#. That was with a 350 and a 4 speed. Not sure what other parts were needed to get the 7500# rating, but my C2500 '70 Sierra Grande 400/402 was rated at the max 7500#.
__________________
44 Willys MB
52 M38A1
64 Corvette Coupe
68 Camaro 'vert LT1 & TH700
69 Z/28 355 12.6's @110
69 Chevy Short Step 4 1/2"/7" drop
72 Jimmy 4WD 4spd 4" & 35's
02 GMC 2500HD 4x4 Duramax
Mike C is online now   Reply With Quote
Old 02-11-2019, 10:22 PM   #22
burnin oil
Registered User
 
Join Date: Jan 2013
Location: Eastern TN
Posts: 1,088
Re: How strong is the frame?

In all honesty the frame would be the least of my concerns. I have seen alot more bent or broken springs than frames. Usually the bent frames where due to someone hooking a logging chain to it when stuck and broken were from rust. So with that in mind I would just get a truck that can handle the weight and make sure the brakes are good to go. I am going out on a limb here and guessing that the truck will be loaded most of the time so unless you are driving 70+ all the time then an OD trans wouldnt even be needed. Let it rev and it will pull like a dream. The newer autos seem to shift alot better but a hunting transmission is annoying when pulling a load. I am old school and still prefer to run a clutch pedal on any hauling truck.
burnin oil is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:11 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Copyright 1997-2013 67-72chevytrucks.com