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Old 06-02-2003, 10:13 PM   #1
4t5acp
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K10 vs K20

This is probably one of those stupid questions, but I figured the correct answer could be found here. What are the differences between a '72 K10 and K20 ,apart from the obvious different drive axles? I suppose the leaf spring packs are different, but am not sure.
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Old 06-03-2003, 05:21 AM   #2
JIMs70GMC
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Only the rear springs are different. The fronts will have either two or three leaves depending on options. Mine had front and rear heavy duty springs, don't remember the RPOs. I also believe on 3/4 tons the rear suspension had 1" blocks. I have a pic in my sig link.
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1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs
1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX
1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears
1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now.....
1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone.
1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed.

1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm
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Old 06-03-2003, 10:09 AM   #3
Yukon Jack
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The Chevy reproduction book that gives stats also shows a difference in frames. Both the K10 and K20 have 39,000 lb-test steel, but the K10's section modulus is 2.70 (KS-KE107 models) and 3.48 for the KS-KE109 models while the K20's section modulus is only 3.48. I think that has to do with the amount of give or elasticity the frame has.
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Old 06-03-2003, 10:18 PM   #4
4t5acp
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Thanks for the info. - knew I had come to the right place to find out.
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Old 06-04-2003, 12:09 AM   #5
mshirey
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Great info regarding the section modulus. I assume that is the elastic section modulus. You are right in that this ratio is an indicator of the frame rail's ability to resist bending. This ratio is highly dependent on the geometry of the cross section of the frame rail. I always thought that the 3/4 ton frames must have a greater height which would provide for a larger section modulus. For those interested, the Elastic Section Modulus (S)=I/c. Where (I) is the moment of inertia of the geometric cross section and (c) is the largest distance from the neutral axis.
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Old 06-04-2003, 08:02 PM   #6
Vince M
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Other differences...Correct me if I'm wrong though.
K10's were available as short beds, K20's were not.
K20's have 8 lug axles as you stated.

I can't say I've ever seen a K10 long bed..well not around here anywhere.
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