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#1 |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Differences between C/K-10 and C/K-20
Besides the uprated springs what are the visible differences between these two frames?
Is the 20 frame taller, heavier, thicker metal, etc? Is there a frame production tag and if so where is it located? ![]() TIA
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k. |
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#2 |
Designated A-hole!
Join Date: Mar 2003
Location: South Mississippi
Posts: 36,450
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It's my understanding that the frames are pretty much the same. The trailing arms may be beefed up a little.
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"If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. ![]() We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck" |
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#3 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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the frame has a little added bracing in a couple areas....but other than that, they are the same.
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#4 |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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So its mostly in the springs then that increases towing and hauling capacity?
Are there any frame build tags? Location?
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k. |
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#5 |
Registered User
Join Date: Jun 2004
Location: Beeville, Texas
Posts: 1,943
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No tags, but part of the truck's VIN number is stamped on the left front frame rail on the top. You might have to wire brush the frame to find it like I did.
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RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck |
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#6 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
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k. |
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#7 |
Registered User
Join Date: Jun 2004
Location: Beeville, Texas
Posts: 1,943
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Yep, sure is.
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RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck |
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#8 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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just behinde the steering gear box on top of the frame rail.
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#9 |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Thanks guys. I am hoping I dont see something disappointing when I see it in person. Be looking at it/picking it up Saturday.
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k. |
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#10 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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The numbers on the frame won't tell you if it is a real 4X4... but if the #'s match the VIN on the truck...you're in luck. (it is only the last 6 or so of the VIN)
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#11 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
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k. |
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#12 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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if that vin is a c******* and not a K******...then yes, it is a conversion.
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#13 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
C = 2wd E = V8 gas 2 = 3/4 ton 4 = pickup 1 = 1971 J = Janesville assembly plant Last 6 digits = serial number of that specific truck So unless I made a mistake in the decode, its definitely originally a C20. Now its a 4wd with 6 lugs on each wheel which seems to mean a K10 underpinnings at least. I hope its no hack job, I'll be seeing it in person tomorrow AM. Here's a pic of hopefully my first 67-72 and a closeup of the left rear tire, maybe some of the sharp-eyed people can say what type of rear suspension that is. I cant make out any leaf springs, so maybe its a trailing arm?
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k. |
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#14 |
Designated A-hole!
Join Date: Mar 2003
Location: South Mississippi
Posts: 36,450
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That's trailing arm(coil), you can see it in front of the tire.
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"If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. ![]() We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck" |
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#15 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
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k. |
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#16 |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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I had to let this one go. The truck was apparently in a pretty severe accident as the frame rails were bent and further the engine was sitting at an angle to the frame rails. On drivers side of the frame where they attached the leaf springs for the 4wd conversion they cut out and didnt replace about an 8"x8" section of the frame rail. It was bad, I could go on but wont. The number was ground off the frame rail BTW. Back to the search.
Like krue said, it had a the trailing arm coil spring rear setup. Now on the way back I saw a Chevy C-20 camper(I think a 69) and it had rear leafs and front coils. Further I saw a 1971 Chevy K-20(all original) with front and rear leafs. So is it maybe the 20s that have the rear leafs and the 10s with the trailing arms, not GMC vs Chevy? Is there a book/CD I can buy on this?
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k. |
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#17 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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there is no definate rule of thumb....some GMC had coils and it wasn't optioned as so.
However, the general rule of thumb that most ppl follow, is Chevy had coils and optional leafs. (c/10 - c/20) GMC had leaf, with optional coils. (again, c/1500 to c/2500) The camper truck you saw, it was either optioned with the leafs, or it could have been a longhorn, which ONLY came with leafs, just like the one ton trucks and all 4X4 trucks. |
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#18 |
Registered User
Join Date: Dec 2004
Location: North Central Colorado
Posts: 38
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From all my research before I converted my K10 to a K20 the only differences I could see were not in the frame. Not sure about a C10 & C20. I only had to swap axle housings & springs, master cylinder & mount, radiator & rear driveshaft. I already had the HD 4spd & transfer case. I have a K20 frame to compare & it is identical to my K10 frame, hard lines & everything.
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'71 K20 Custom Deluxe - 1 owner - Original 350 & 4 spd, Rams horn dual exhaust, Centerforce clutch, K&N 4"x15", factory tow hooks, 4" Skyjacker Softride, Rancho RSX9000s, custom Firestone AirRide overloads, 36" 305/85R16 10ply Buckshot Mudders, 4.11 gears |
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#19 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
Cyber, can you got into a little more detail on each of those and why they needed to be swapped? You swapped axle housings and axles too correct? Springs I got. Why the master cylinder, ms mount? Larger brakes on the 20 need more fluid? Radiator? Rear driveshaft? The rear driveshaft I am guessing because of the larger diff housing and/or yoke?
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k. |
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#20 | |
Registered User
Join Date: Dec 2004
Location: North Central Colorado
Posts: 38
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Quote:
I swapped both front & rear axles. The K10 had a Dana 44 front & Corporate 12 bolt rear. The K20 also had a Dana 44 front, but with much larger axle tubes, shafts, u-joints & knuckles as well as larger calipers, 8 bolt hubs & 8 bolt spindles & locking hubs. The K10 was 3.73 gears standard. The K20 was 4.11 gears standard. The master cylinder was much larger volume-wise as were all the brake components. The K20 master cylinder mount is considerably different than the K10 & the two will not interchange. They also use a different brake booster as well. I also used all stainless steel braided flex brake lines. It vastly reduced the mushiness of the brakes, not that they were that mushy to start with. Spend the money, its worth it. One thing to note. Virtually every rear axle on a K20 I've run across in Colorado as an owner & as a former mechanic do not match the specs in any parts book or GM specs. All the books & specs say they have 12"x2" brakes. Mine & virtually every one I've seen had a Dana 60 diff, 12"x2½" brakes & 1 1/8" wheel cylinders. None of the rear brake parts match the books either. The drums I've had to simply match w/ existing b/c none of the books listed the correct drums. Same for the small parts kit (springs, levers, retainers, etc., etc.) & wheel cylinders. Most parts stores list these rear axles as only havin' been installed in C20s with leaf springs & not always. Don't know where the disconnect comes from. Depending on the book, the drums & cylinders match those from a G30, stepvan, but not always. Go figure. The standard K10 w/o A/C used a 2 core radiator unless it had a plow package, then it was 3 core. The standard K20 w/o A/C used a 3 core radiator unless it had the "plow" package or "camper/towing" package & then is was 4 core. The front yoke on the rear driveshaft was identical to the K10. The K20 used a larger diameter tube, different rear yoke & was shorter. The Dana 60 has a much longer (front-to-back) housing than the 12 bolt, hence the shorter driveshaft. Of course I had to modify mine for the lift as well. Another funny thing is Skyjacker sells the same springs in the Softride 4" kit for both the K10 & K20. The rear springs work great offroad, but will not carry much of any load--even less than the stock K10 springs. That is why I added from long travel air bags to act as overloads. They don't affect axle travel when offroad, but do allow me to tow & carry the same load as a regular K20.
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'71 K20 Custom Deluxe - 1 owner - Original 350 & 4 spd, Rams horn dual exhaust, Centerforce clutch, K&N 4"x15", factory tow hooks, 4" Skyjacker Softride, Rancho RSX9000s, custom Firestone AirRide overloads, 36" 305/85R16 10ply Buckshot Mudders, 4.11 gears Last edited by CyberRanger; 07-24-2005 at 04:57 PM. |
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#21 | |
Registered User
Join Date: Oct 2000
Location: St. Johns, Arizona
Posts: 2,660
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Quote:
All 67-72 four wheel drives have leaf springs. Four wheel drive frames are straight over the rear axle (when looking at it from above). Two wheel drive frames bow out, I think even on two wheel drives with leafs.
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my 2¢ - t.i.o.l.i. Bowen 1968 K20 fleet 1969 K10 swb fleet 1972 K10 Suburban 1972 C10 lwb step 1992 K1500 'burb 1995 K2500 'burb 1997 C1500 'burb 1999 K1500 2000 K1500 'burb Why do I own so many Suburbans? |
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#22 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
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k. |
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#23 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
LH, FWIW, the C20 was not a longhorn.
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k. Last edited by kobayashi; 07-24-2005 at 03:18 PM. |
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#24 |
its all about the +6 inches
Join Date: Jan 2001
Location: Hilliard Ohio
Posts: 2,693
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on the 2 wheel drive coil spring frames, there is additional bracing...someone on here has pics. He took the pics after he bought a 3/4 ton frame while working on a 1/2 ton and discovered the new frame was not 100% right.
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#25 | |
Registered User
Join Date: Jul 2005
Location: Magnolia State
Posts: 27
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Quote:
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