Axle shafts and 3/4 & 1ton - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*wolfthing2000* · 11-09-2004, 11:32 PM

I am in the process of finding a 3rd member 4;56 ratio for a 69 K 20 rear axle.. That is the corporate axle dropout style( Eaton?). I have been told to look out for the spline count for the axle shafts as they differ for 3/4 and 1 tons.. The guy told me to check hex size on the axle flange bolts:::::::::: 3/4 inch ( what I have on the K-20 which to my knowledge came with the truck from factory) indicates a 1 ton. In other words it takes a 3/4 socket or wrench to remove the bolts. But he says the 3/4 ton axle has 5/8 bolts and a different spline count????

What is there to this?? Any fact here or just backyard talk??

I will pull an axle before I head to the salvage yard to be sure.
Thanks,

Dave

1969 GMC · 11-09-2004, 11:43 PM

The spline count is the same. Not sure about the nut size.

*wolfthing2000* · 11-10-2004, 01:07 PM

Does it matter what years?? ie: 52, 57,68 69, are all the same????

Fred T · 11-10-2004, 03:30 PM

Different years have different axle lengths. There is also some variation on length between the 3/4 & 1 ton. If you have the standard 10 bolt, non-posi what you need is the pumpkin out of a 64-72 3/4 or 1 ton. There was not a ratio higher than 4.56 before '64. About all you will find for higher gears is the 4.10, and they are getting scarce. I have heard of one guy on the stovebolt board finding a 3.73 out of a blazer, but that's it.

If you want better gears, get a 14 bolt out of a later model truck and replace the entire differential. there are a lot of them with 3.73, some of the later models even had 3.42 gears.

**Stocker** · 11-10-2004, 08:03 PM

My K20 axle bolts take a 3/4" socket. Stock (afaik) Eaton HO52 with 4.10s, coulda told you how many splines a couple weeks ago...

**JIMs70GMC** · 11-10-2004, 09:07 PM

For some reason I'm thinking 17 splines.

Rod · 11-10-2004, 10:32 PM

17 it is.

11-09-2004, 11:32 PM	#1
wolfthing2000 Account Suspended Join Date: Oct 2004 Posts: 1,276	Axle shafts and 3/4 & 1ton I am in the process of finding a 3rd member 4;56 ratio for a 69 K 20 rear axle.. That is the corporate axle dropout style( Eaton?). I have been told to look out for the spline count for the axle shafts as they differ for 3/4 and 1 tons.. The guy told me to check hex size on the axle flange bolts:::::::::: 3/4 inch ( what I have on the K-20 which to my knowledge came with the truck from factory) indicates a 1 ton. In other words it takes a 3/4 socket or wrench to remove the bolts. But he says the 3/4 ton axle has 5/8 bolts and a different spline count???? What is there to this?? Any fact here or just backyard talk?? I will pull an axle before I head to the salvage yard to be sure. Thanks, Dave

11-09-2004, 11:43 PM	#2
1969 GMC Registered User Join Date: Feb 2003 Location: The Rubber City Posts: 5,498	The spline count is the same. Not sure about the nut size. __________________ 1969 GMC K2500 1996 Honda Accord 2007 Kawasaki KLR 650

11-10-2004, 03:30 PM	#4
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Different years have different axle lengths. There is also some variation on length between the 3/4 & 1 ton. If you have the standard 10 bolt, non-posi what you need is the pumpkin out of a 64-72 3/4 or 1 ton. There was not a ratio higher than 4.56 before '64. About all you will find for higher gears is the 4.10, and they are getting scarce. I have heard of one guy on the stovebolt board finding a 3.73 out of a blazer, but that's it. If you want better gears, get a 14 bolt out of a later model truck and replace the entire differential. there are a lot of them with 3.73, some of the later models even had 3.42 gears. __________________ Fred There is no such thing as too much cam...just not enough engine. Last edited by Fred T; 11-11-2004 at 12:56 AM.

11-10-2004, 08:03 PM	#5
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,669	Fwiw, My K20 axle bolts take a 3/4" socket. Stock (afaik) Eaton HO52 with 4.10s, coulda told you how many splines a couple weeks ago... __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

11-10-2004, 09:07 PM	#6
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	For some reason I'm thinking 17 splines. __________________ 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

11-10-2004, 01:07 PM	#3
wolfthing2000 Account Suspended Join Date: Oct 2004 Posts: 1,276	Does it matter what years?? ie: 52, 57,68 69, are all the same????

11-10-2004, 10:32 PM	#7
Rod Join Date: Dec 1999 Location: Eastern - Manitoba Canada, Winnipeg Posts: 4,369	17 it is. __________________ 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.



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