1981 12 bolt direct swap into 86 swb 10 bolt? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bobs86silv · 03-29-2009, 02:54 PM

Ok I finally found a rearend with 3.73 gears. They are from a 1981 1/2 ton two wheel drive long bed. I would like to swap the rearend under my 86 swb 1/2 ton. I have dont alot of reading, and I can swap my backing plate and breaks and it should bolt right in right? Am I really going to have a drive shaft that is an inch too short? Is there an easy fix for this? There are quite a few 88,89,90 rearends I can get but I dont think they will work will they?

Thanks
Robert

rockn30809 · 03-29-2009, 03:36 PM

I didn't swap backing plates and my drive shaft length was fine. All I had to do was get a conversion u-joint. My truck is a 87.

80stepsideguy · 03-29-2009, 06:09 PM

Everything is a direct bolt in to your truck.81 was the last year of the 12 bolts as 82 and on were all 10 bolts in 1/2 ton trucks.Your original plates and u bolts should be a perfect fit as well as the e brake cables.I got a 3.73 rearend in my truck project as well but opted for the 700r4 due to the higher rpms the rearend will bring..

thanks
pat

gchemist · 03-29-2009, 08:46 PM

Yes, I swapped a 77 12 bolt into my 83. You will have to change the rear u-joint. The 12 bolt u-joints have smaller caps.....or the 10 bolt does. I can't remember which one. Either way two will be large and two will be small.

silvereagle07 · 03-29-2009, 10:38 PM

Does anyone know the part number on the conversion u joint? I install a 12 bolt on my 84' but I forgot what the number was.

rockn30809 · 03-30-2009, 07:35 PM

Quote:

Originally Posted by silvereagle07

Does anyone know the part number on the conversion u joint? I install a 12 bolt on my 84' but I forgot what the number was.

precision is #372, spicer is 5-3022x

03-29-2009, 02:54 PM	#1
bobs86silv Registered User Join Date: Apr 2005 Location: Sedalia, Mo Posts: 326	1981 12 bolt direct swap into 86 swb 10 bolt? Ok I finally found a rearend with 3.73 gears. They are from a 1981 1/2 ton two wheel drive long bed. I would like to swap the rearend under my 86 swb 1/2 ton. I have dont alot of reading, and I can swap my backing plate and breaks and it should bolt right in right? Am I really going to have a drive shaft that is an inch too short? Is there an easy fix for this? There are quite a few 88,89,90 rearends I can get but I dont think they will work will they? Thanks Robert __________________ 86 Silverado SWB 350/350/3.08 9.7-1 Forged pistons Eagle Rods Eagle Crank Zero Deck Balanced Blueprinted 180cc DART Heads Roller Rockers RPM Intake Demon Carb Flowtech Headers 400HP/400TQ

03-29-2009, 03:36 PM	#2
rockn30809 Registered User Join Date: Mar 2009 Location: South Carolina Posts: 93	Re: 1981 12 bolt direct swap into 86 swb 10 bolt? I didn't swap backing plates and my drive shaft length was fine. All I had to do was get a conversion u-joint. My truck is a 87.

03-29-2009, 08:46 PM	#4
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Re: 1981 12 bolt direct swap into 86 swb 10 bolt? Yes, I swapped a 77 12 bolt into my 83. You will have to change the rear u-joint. The 12 bolt u-joints have smaller caps.....or the 10 bolt does. I can't remember which one. Either way two will be large and two will be small. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

03-29-2009, 10:38 PM	#5
silvereagle07 Registered User Join Date: Sep 2008 Location: Bailey, NC Posts: 2,462	Re: 1981 12 bolt direct swap into 86 swb 10 bolt? Does anyone know the part number on the conversion u joint? I install a 12 bolt on my 84' but I forgot what the number was. __________________ Jeramy '84 GMC project truck '85 Chevy 4X4 SOLD '07 Chevy Trailblazer SS 5th Annual SHPHC Car/Truck Show Pics http://67-72chevytrucks.com/vboard/s...d.php?t=543605 UPDATED PICS! CHECK 'EM OUT Last edited by silvereagle07; 03-29-2009 at 10:39 PM. Reason: part number

03-29-2009, 06:09 PM	#3
80stepsideguy Laid back freak Join Date: Mar 2008 Location: hastings florida Posts: 248	Re: 1981 12 bolt direct swap into 86 swb 10 bolt? Everything is a direct bolt in to your truck.81 was the last year of the 12 bolts as 82 and on were all 10 bolts in 1/2 ton trucks.Your original plates and u bolts should be a perfect fit as well as the e brake cables.I got a 3.73 rearend in my truck project as well but opted for the 700r4 due to the higher rpms the rearend will bring.. thanks pat __________________ 1980 chevy c10 step side restomod, 1970 cougar convertible 1 OF 24 ever built: 2014 Hyundai Tucson limited (daily driver). Last edited by 80stepsideguy; 03-29-2009 at 08:55 PM.



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