help with year of K20 chassis - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Tully · 02-12-2005, 10:18 AM

I have a 3/4 ton 4x4 chassis under a 71 GMC 4x2 body. I am not sure of the year of the chassis, it has disc brakes, hub size for rims are 4 3/4" (see pictures), and the front leafs are 3" wide.

Mudder · 02-12-2005, 12:55 PM

Sounds like a newer frame like mine but those that really know will help ya out.

Mudder · 02-12-2005, 01:33 PM

Ok Tulley after giving you crap over on the other board for douple posting hehe, few questions about your frame. Does it have a sway bar? Are there extra holes where the cab mounts? I have a 77 chassis and it has 3 inch wide springs.

Rod · 02-12-2005, 02:25 PM

3inch wide leafs I believe are 73 up.

Tully · 02-12-2005, 04:50 PM

Mudder, there are no extra holes in the frame but I have come to the conclusion that the PO put 73 up front springs under it. The brackets and shackles are bolted on. The rear shock and spring mounts are riveted on so they didn't try shortening a 73 up chassis. I started sanding through the caked rust to try and find the frame number I will let you know what I find.

Blazer1970 · 02-12-2005, 05:50 PM

Get the BOM number off the front Dana 44. It will tell you the original year and application.

**JIMs70GMC** · 02-12-2005, 08:15 PM

Are the leaves 3" over the whole length of the spring? Stock for my 70 and 71 were 3" wide at each end and 2.5" in the center. 2nd, on the 3/4 tons I believe the internal style hub showed up in 76 or 77, before that they were all external style. Measure the length of the front springs, 73 and up springs are 3" longer than the 72 and earlier springs.

Tully · 02-12-2005, 09:14 PM

Tim, the numbers I found on the dana 44 are C-31256 287 44 5F
Jim, you are right the springs are 3'' at both ends and 21/2" in the middle. I never noticed that before. With weight on it they measure 43 3/4", hole center to hole center.

Blazer1970 · 02-13-2005, 05:05 PM

Quote:

Originally Posted by Tully

Tim, the numbers I found on the dana 44 are C-31256 287 44 5F
Jim, you are right the springs are 3'' at both ends and 21/2" in the middle. I never noticed that before. With weight on it they measure 43 3/4", hole center to hole center.

The BOM number is a 6 digit number that will be stamped on the front of the axle tube to the right of the pumpkin when looking under the front of the truck. You will likely have to sand some rust off the tube to reveal the numbers.

**JIMs70GMC** · 02-13-2005, 07:52 PM

Tully, those are pre 73 springs. Same length as both my trucks. 73 and up are 46" long. I say your axle is a late 70s and your frame is pre 73 maybe even a converted 2wd truck.

Tully · 02-13-2005, 08:55 PM

Tim, I sanded down and found 10 20 1A4 603351 3

Jim, I think you just nailed it. Its a 2wd body and they put the front differential under it, that's why it's bolted. To do this they had to lift the truck because of the low hump. ( I put a high hump in and dropped it back down). The only other thing that puzzles me is the large rims needed. The only rims I have found are Ford, chrysler and some white spokes that will fit. In fact the chrysler ones only work up front.

1969 GMC · 02-13-2005, 09:41 PM

603351
DANA 44 FRONT
Year 1972
Make CHEVY
Model K5 Blazer, K10 1/2 Ton Pickup & Suburban & Panel Truck
Number of axle splines: 30 FULL

hope it helps!

poff · 02-15-2005, 12:34 PM

The VIN number should be stamped in the frame somewhere.

Tully · 02-15-2005, 09:09 PM

I looked for the Vin # on top of the frame rail by the power steering pump and nothing there. Where else should I look?

Rod · 02-16-2005, 08:54 PM

Its under the cab also....but can't really be seen without removing the cab.

If" 1969 GMC "found info on dating your front axle..it could be that some one just swapped out the locking hub style to newer version locking hubs, and the hub its self. It can be done and might of had to have been done that way as parts for the 70-72 style 3/4 ton locking hubs are hard to find.

DennyB · 02-16-2005, 10:02 PM

If its a converted 2wd chassis, a hole would have to be drilled in the frame for the rear shackle to mount (on the front diff.)

Here.........

Tully · 02-18-2005, 09:56 AM

Denny, yes it looks like the rear shackles were added, they cobbled some steel plates on the outside of the frame that covers up the hole they cut.

02-12-2005, 10:18 AM	#1
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	help with year of K20 chassis I have a 3/4 ton 4x4 chassis under a 71 GMC 4x2 body. I am not sure of the year of the chassis, it has disc brakes, hub size for rims are 4 3/4" (see pictures), and the front leafs are 3" wide. Attached Images Last edited by Tully; 02-12-2005 at 12:45 PM.

02-12-2005, 02:25 PM	#4
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	3inch wide leafs I believe are 73 up. __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.

02-12-2005, 05:50 PM	#6
Blazer1970 Registered User Join Date: Dec 1999 Location: Old Mission, MI, USA Posts: 2,510	Get the BOM number off the front Dana 44. It will tell you the original year and application. __________________ Tim

02-12-2005, 08:15 PM	#7
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Are the leaves 3" over the whole length of the spring? Stock for my 70 and 71 were 3" wide at each end and 2.5" in the center. 2nd, on the 3/4 tons I believe the internal style hub showed up in 76 or 77, before that they were all external style. Measure the length of the front springs, 73 and up springs are 3" longer than the 72 and earlier springs. __________________ 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

02-13-2005, 07:52 PM	#10
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Tully, those are pre 73 springs. Same length as both my trucks. 73 and up are 46" long. I say your axle is a late 70s and your frame is pre 73 maybe even a converted 2wd truck. __________________ 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

02-12-2005, 12:55 PM	#2
Mudder Registered User Join Date: Feb 2001 Location: East Central, MO Posts: 11,336	Sounds like a newer frame like mine but those that really know will help ya out.

02-12-2005, 01:33 PM	#3
Mudder Registered User Join Date: Feb 2001 Location: East Central, MO Posts: 11,336	Ok Tulley after giving you crap over on the other board for douple posting hehe, few questions about your frame. Does it have a sway bar? Are there extra holes where the cab mounts? I have a 77 chassis and it has 3 inch wide springs.

02-12-2005, 04:50 PM	#5
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Mudder, there are no extra holes in the frame but I have come to the conclusion that the PO put 73 up front springs under it. The brackets and shackles are bolted on. The rear shock and spring mounts are riveted on so they didn't try shortening a 73 up chassis. I started sanding through the caked rust to try and find the frame number I will let you know what I find.

02-12-2005, 09:14 PM	#8
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Tim, the numbers I found on the dana 44 are C-31256 287 44 5F Jim, you are right the springs are 3'' at both ends and 21/2" in the middle. I never noticed that before. With weight on it they measure 43 3/4", hole center to hole center.

02-13-2005, 08:55 PM	#11
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Tim, I sanded down and found 10 20 1A4 603351 3 Jim, I think you just nailed it. Its a 2wd body and they put the front differential under it, that's why it's bolted. To do this they had to lift the truck because of the low hump. ( I put a high hump in and dropped it back down). The only other thing that puzzles me is the large rims needed. The only rims I have found are Ford, chrysler and some white spokes that will fit. In fact the chrysler ones only work up front.

02-13-2005, 09:41 PM	#12
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	603351 DANA 44 FRONT Year 1972 Make CHEVY Model K5 Blazer, K10 1/2 Ton Pickup & Suburban & Panel Truck Number of axle splines: 30 FULL hope it helps! __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

02-15-2005, 12:34 PM	#13
poff Registered User Join Date: Dec 1999 Location: san diego, ca Posts: 546	The VIN number should be stamped in the frame somewhere. __________________ '70 K-20 San Diego, CA

02-15-2005, 09:09 PM	#14
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	I looked for the Vin # on top of the frame rail by the power steering pump and nothing there. Where else should I look?

02-16-2005, 08:54 PM	#15
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	Its under the cab also....but can't really be seen without removing the cab. If" 1969 GMC "found info on dating your front axle..it could be that some one just swapped out the locking hub style to newer version locking hubs, and the hub its self. It can be done and might of had to have been done that way as parts for the 70-72 style 3/4 ton locking hubs are hard to find. __________________ Senior active founding member. 70 3/4 ton GMC Suburban 4x4 250/4 spd. 71 1/2 ton Suburban Chevy 4x4, 350/350 72 Chev 1 ton tow truck 402BB w/Holmes 440 wrecker on propane 2005 FLSTSCI Harley Springer 85 FXSB Harley Lowrider 72 Triumph 650 Bonneville 5spd "Poor people don't have hobbies" Quote from wife.

02-16-2005, 10:02 PM	#16
DennyB Led Sled! Discs R 4 ME! Join Date: Jan 2001 Location: Toms River, NJ, USA (Transplanted Hoosier) Posts: 7,327	If its a converted 2wd chassis, a hole would have to be drilled in the frame for the rear shackle to mount (on the front diff.) Here......... Attached Images __________________ "Never ride faster than your Angel can fly" I.M.O.M,W,J&C Patriot Guard Rider



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02-18-2005, 09:56 AM	#17
Tully Registered User Join Date: Jan 2005 Location: Hiles, WI Posts: 42	Denny, yes it looks like the rear shackles were added, they cobbled some steel plates on the outside of the frame that covers up the hole they cut.

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