4x4 1/2 T vs. 3/4 T Drive Shaft - Same? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Ironhorse** · 03-20-2013, 07:56 AM

Looking for an answer since I have no idea. Is a rear drive shaft from a 1/2 ton 4x4 LWB verses a rear drive shaft from a 3/4 ton 4x4 LWB inter-changeable or compatible? Have a shaft from my 1/2 ton 4x4 for sale on the parts board and a fellow member is interested but is looking for a drive shaft for his 3/4 ton 4x4. Will the shaft I have work for him? Both trucks are '71-'72 sm465/np205 set-ups.

ERASER5 · 03-20-2013, 10:07 AM

U-joint is a different size most likely. Mine was. The length might work, might not. The 3/4 ton sits taller than the 1/2 ton making the D-shaft slightly longer. Think of a triangle with the hight being the truck, and the length being the linear distance from the front U-joint to the axel. The d-shaft is the hypotenuse. As the hight get taller, the d-shaft get longer. The slip joint can only absorb so much difference. On my truck, I am hoping the new springs will give some lift so I don't have to cut my d-shaft. I only have a bit more than a 1/4 inch of movement in one direction.

**argonaut** · 03-20-2013, 04:45 PM

Its also dependent on powertrain and towing capacity. The more powerful the motor the larger diameter, or thicker the walls or the driveshaft to withstand the torque. Same thing for u-joint sizes. And same thing if you are hauling/towing heavier loads, the drivetrain is subject to greater forces and torques.

odog · 03-20-2013, 10:38 PM

I took the drive shaft from my3/4 ton 67 and put it in my1/2 ton 69. No difference. Both were 4x4. The 3/4 ton had an Eaton rear end with an sm 420/221 trans transfer combo and the 69 had the same trans transfer combo but a 12 bolt rear end. No problems, the drive shaft was a 2 piece with a carrier bearing.
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budman k20 · 03-20-2013, 11:29 PM

I have never seen a 2 pc driveshaft on a 4x4? Must be pre 71 technology. I know for a fact my 72 3/4 4x4 has larger u-joints than my 71 1/2 ton 4x4. Same for the front shaft as well.
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mud.man.rj · 03-20-2013, 11:40 PM

I have done it before and believe the ujoint size was different so I used the combo joint which is 2 different cup sizes so fits shaft and fits pinion.

**Ironhorse** · 03-21-2013, 10:14 AM

Thanks for the replies on the drive shaft question. Seems like others have done it but does involve using differant u-joints. Will PM the interested party and let him decide. Again, thanks for the replies, always learning from this board.

odog · 03-21-2013, 09:51 PM

Sorry, I forgot to say I used a combo u joint on the rear end, everything else was the same though.
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03-20-2013, 07:56 AM	#1
Ironhorse Senior Member Join Date: Jul 2001 Location: Wellington, Ks Posts: 10,337	4x4 1/2 T vs. 3/4 T Drive Shaft - Same? Looking for an answer since I have no idea. Is a rear drive shaft from a 1/2 ton 4x4 LWB verses a rear drive shaft from a 3/4 ton 4x4 LWB inter-changeable or compatible? Have a shaft from my 1/2 ton 4x4 for sale on the parts board and a fellow member is interested but is looking for a drive shaft for his 3/4 ton 4x4. Will the shaft I have work for him? Both trucks are '71-'72 sm465/np205 set-ups. __________________ 1971 Chevy 1/2T 4x4 LWB 350 V-8 Was sm465-now 350TH/np205 Tilt, Tach, Towhooks Original Truck AM/FM Wellington, Ks

03-20-2013, 10:07 AM	#2
ERASER5 Registered User Join Date: Jun 2006 Location: Indiana Posts: 4,859	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? U-joint is a different size most likely. Mine was. The length might work, might not. The 3/4 ton sits taller than the 1/2 ton making the D-shaft slightly longer. Think of a triangle with the hight being the truck, and the length being the linear distance from the front U-joint to the axel. The d-shaft is the hypotenuse. As the hight get taller, the d-shaft get longer. The slip joint can only absorb so much difference. On my truck, I am hoping the new springs will give some lift so I don't have to cut my d-shaft. I only have a bit more than a 1/4 inch of movement in one direction. __________________ '70 GMC C1500 LWB Power disc brakes. WooHoo! Posi 6 Lug Dana 60

03-20-2013, 04:45 PM	#3
argonaut Senior Member Join Date: Aug 2008 Location: Long Beach, CA Posts: 1,813	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? Its also dependent on powertrain and towing capacity. The more powerful the motor the larger diameter, or thicker the walls or the driveshaft to withstand the torque. Same thing for u-joint sizes. And same thing if you are hauling/towing heavier loads, the drivetrain is subject to greater forces and torques. __________________ Jason M. @argonaut62 1972 K5 Blazer CST, Turquoise 1966 K20 Short Fleet Pickup, Big Ugly 1964 C10 Short Fleet, Gertrude 2001 Porsche 911 Carrera 1996 Ford Bronco XLT 1980 Jeep Wagoneer 2008 Honda CBR1000RR 2005 Honda RC51 1981 Honda CB750C No dis-assemble Johnny Five! No dis-assemble!

03-20-2013, 10:38 PM	#4
odog Registered User Join Date: Oct 2007 Location: Wendell, Idaho Posts: 608	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? I took the drive shaft from my3/4 ton 67 and put it in my1/2 ton 69. No difference. Both were 4x4. The 3/4 ton had an Eaton rear end with an sm 420/221 trans transfer combo and the 69 had the same trans transfer combo but a 12 bolt rear end. No problems, the drive shaft was a 2 piece with a carrier bearing. Posted via Mobile Device __________________ 1969 4x4 Nothing beats a good rock drill and some dynamite

03-20-2013, 11:29 PM	#5
budman k20 1972 K20 Join Date: Apr 2008 Location: Greenfield MN Posts: 360	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? I have never seen a 2 pc driveshaft on a 4x4? Must be pre 71 technology. I know for a fact my 72 3/4 4x4 has larger u-joints than my 71 1/2 ton 4x4. Same for the front shaft as well. Posted via Mobile Device

03-20-2013, 11:40 PM	#6
mud.man.rj Registered User Join Date: Dec 2011 Location: Creighton Sask. Canada Posts: 4,121	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? I have done it before and believe the ujoint size was different so I used the combo joint which is 2 different cup sizes so fits shaft and fits pinion.

03-21-2013, 10:14 AM	#7
Ironhorse Senior Member Join Date: Jul 2001 Location: Wellington, Ks Posts: 10,337	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? Thanks for the replies on the drive shaft question. Seems like others have done it but does involve using differant u-joints. Will PM the interested party and let him decide. Again, thanks for the replies, always learning from this board. __________________ 1971 Chevy 1/2T 4x4 LWB 350 V-8 Was sm465-now 350TH/np205 Tilt, Tach, Towhooks Original Truck AM/FM Wellington, Ks

03-21-2013, 09:51 PM	#8
odog Registered User Join Date: Oct 2007 Location: Wendell, Idaho Posts: 608	Re: 4x4 1/2 T vs. 3/4 T Drive Shaft - Same? Sorry, I forgot to say I used a combo u joint on the rear end, everything else was the same though. Posted via Mobile Device __________________ 1969 4x4 Nothing beats a good rock drill and some dynamite



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