10 & 12 bolt u-joint the same? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

low 84 · 02-28-2003, 02:51 PM

if i'm swapping from an '84 10 bolt to a '75 12 bolt, is the rear u joint the same? so will it bolt right up, or do i need a different u joint? i know perches and width ect are all the same so it will fit right in just not sure bout hookin the driveshaft up.

RockHQ · 02-28-2003, 03:17 PM

I believe it is different.

gchemist · 02-28-2003, 03:17 PM

Unless you use the 12 bolt drive shaft you need a different u-joint. Part number 372 Spicer from Napa if I remember correctly. The caps for both are different sizes. To convert to the 12 bolt, you need a joint with two large caps and two small caps. I know, I destroyed one already and replaced it with the Spicer. The spicer U joints seems to be tighter too.

ElGracho · 02-28-2003, 04:30 PM

The 12 bolt originally used a 1310 ujoint, the 10 bolt originally used a 3R ujoint. I have a 3R yoke for the 12 bolt that I put in my 84, not installed yet, but it will allow me to have a 12 bolt and the larger 3R ujoint which will also be the same as the front ujoint in the rear shaft and a little easier to find if one breaks on the road.

low 84 · 02-28-2003, 10:03 PM

so i will need to use the two larger caps off the 12 bolt and a u joint for a 12 bolt, correct? anything else i need?

BaggedC10 · 02-28-2003, 10:39 PM

My 12-bolt rear-end has the same yoke from my factory 10-bolt unit.

02-28-2003, 02:51 PM	#1
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	10 & 12 bolt u-joint the same? if i'm swapping from an '84 10 bolt to a '75 12 bolt, is the rear u joint the same? so will it bolt right up, or do i need a different u joint? i know perches and width ect are all the same so it will fit right in just not sure bout hookin the driveshaft up. __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

02-28-2003, 03:17 PM	#2
RockHQ ROCKET POWER! Join Date: Feb 2003 Location: Finland, Europe Posts: 509	I believe it is different. __________________ What did i do last nite? I had a wonderful time, That's what they tell me What did i do last nite? 1979 C-10 shortfleet: Olds 350, Th400, 12 bolt Current project: 1969 Olds 455 W-30, needing a rebuild

02-28-2003, 03:17 PM	#3
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Unless you use the 12 bolt drive shaft you need a different u-joint. Part number 372 Spicer from Napa if I remember correctly. The caps for both are different sizes. To convert to the 12 bolt, you need a joint with two large caps and two small caps. I know, I destroyed one already and replaced it with the Spicer. The spicer U joints seems to be tighter too. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

02-28-2003, 04:30 PM	#4
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,553	The 12 bolt originally used a 1310 ujoint, the 10 bolt originally used a 3R ujoint. I have a 3R yoke for the 12 bolt that I put in my 84, not installed yet, but it will allow me to have a 12 bolt and the larger 3R ujoint which will also be the same as the front ujoint in the rear shaft and a little easier to find if one breaks on the road. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

02-28-2003, 10:03 PM	#5
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	so i will need to use the two larger caps off the 12 bolt and a u joint for a 12 bolt, correct? anything else i need? __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

02-28-2003, 10:39 PM	#6
BaggedC10 Under construction! Join Date: Aug 2002 Location: NorCal Posts: 1,065	My 12-bolt rear-end has the same yoke from my factory 10-bolt unit. __________________ 2001 Silverado bagged on 22's. Sold



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