Rear end question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

krue · 03-19-2007, 06:15 PM

My friend has a 86 swb GMC 1/2ton with 2.73 gears, he also has a posi rear out of an 84 Trans Am. Are the rearends the same, can he swap just the gears? Inquiring minds want to know.

Srubydo1986 · 03-19-2007, 06:18 PM

If there both 10 bolts. I believe they would be the same housing so i see why not.

**swervin ervin** · 03-19-2007, 07:23 PM

84 Trans Am is a 10 bolt but the ring gear is a 7.5" or 7.625" where the 10 bolt corporate rear in the truck is a 8.5" ring gear, so the answer to your question is no, you can't swap gears. I'm pretty sure 81 was the last year the 8.5" ring gear was in the F bodies.

Srubydo1986 · 03-19-2007, 08:33 PM

what if they move the mounting points would that work. If they are the same length

Pyrotechnic · 03-20-2007, 01:06 AM

The 2 rear ends dont have much if anything in common besides the 10 bolts.

The best bet if you want to go all out with gears and posi is to find a used 12 bolt and have it rebuilt with the gears and posi unit you want. You could do this with the 10 bolt but I personally wouldn't feel good about investing money in a 10 bolt as it's not as strong. If you only plan to run a stock 350 for street driving though, a 10 bolt is fine. Since you want to put in a posi and lower gears, it sounds like you want to go fast, so a 12 bolt would be the best option.

hiway · 03-20-2007, 06:56 AM

Not to mention the small 10 bolt from the car is very WEAK.

Srubydo1986 · 03-20-2007, 11:34 AM

I dont know why people dont like the chevy 10 bolt , like an unwanted red head step child.

My chevelle has a 10 bolt and when the car was running I drove the car like a race car (speed scares me but 100 in the car) mud truck Got stuck in a car show just hit the gas a through some mud) and a rally car (lot of gravel roads around here 85 most of the time and drifting corners).

Just my 2 cent all my 10 bolt have dont very well except for the one in my old 86 c10 the rod in the main case bored to hole from being round to oval. But that can happen in a 12 bolt to.

bent · 03-20-2007, 12:49 PM

So is their any rear end that you can slide into place and have posi i know 10 bolts are ok because i had a 82 long bed that was a 10 bolt posi and i beat the crap outta it but all asideis their any rear end that will fit my 80 chevy long wide 1/2 ton

jimfulco · 03-21-2007, 12:20 AM

Quote:

Originally Posted by bent

So is their any rear end that you can slide into place and have posi i know 10 bolts are ok because i had a 82 long bed that was a 10 bolt posi and i beat the crap outta it but all asideis their any rear end that will fit my 80 chevy long wide 1/2 ton

A '73-'87 half-ton rear should bolt in, except for the driveshaft. The 10-bolt has a longer "snout" than a 12-bolt, and most likely will require a shorter driveshaft. My 10-bolt ('84) also had a larger U-joint than the old 12-bolt ('79), so I had to get a conversion U-joint.

crm318 · 03-21-2007, 01:07 AM

something else to think about: i had a 71 cutlass with a 10 bolt rear and i bought it a posi from an 80s half ton truck. it had a 31 spline axle and the car 10 bolt had a 28 spline axle. i dont think that the car and truck posi are compatable because of that reason.

03-19-2007, 06:15 PM	#1
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Rear end question My friend has a 86 swb GMC 1/2ton with 2.73 gears, he also has a posi rear out of an 84 Trans Am. Are the rearends the same, can he swap just the gears? Inquiring minds want to know. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

03-19-2007, 06:18 PM	#2
Srubydo1986 The Crazy Machanic Join Date: Jan 2007 Location: Nokesville Va Posts: 1,437	Re: Rear end question If there both 10 bolts. I believe they would be the same housing so i see why not. __________________ 1986 Sliverado longbed 400 small block mean as hell, 700r4 trans (5 speed coming one day) 1970 chevelle 2dr sedan Latest update June 24 2007. *1957 4 door stationwagon - pink all original needing a good restore (body great, floors bad) newest additions 1965 shortbed fleet great granddads. Been told im nuts to bring it back from the dead (still going to happen) plans-all stock with a turbo 292 inline 3 speed column shift. and thats it big block 427 and 5 speed trans and ford 9 inch theyhave no home yet thinking what to put them in and a 79 c60 trash truck um no idea i have one

03-19-2007, 07:23 PM	#3
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Re: Rear end question 84 Trans Am is a 10 bolt but the ring gear is a 7.5" or 7.625" where the 10 bolt corporate rear in the truck is a 8.5" ring gear, so the answer to your question is no, you can't swap gears. I'm pretty sure 81 was the last year the 8.5" ring gear was in the F bodies. __________________ Mike 1985 Chevy C-10

03-19-2007, 08:33 PM	#4
Srubydo1986 The Crazy Machanic Join Date: Jan 2007 Location: Nokesville Va Posts: 1,437	Re: Rear end question what if they move the mounting points would that work. If they are the same length __________________ 1986 Sliverado longbed 400 small block mean as hell, 700r4 trans (5 speed coming one day) 1970 chevelle 2dr sedan Latest update June 24 2007. *1957 4 door stationwagon - pink all original needing a good restore (body great, floors bad) newest additions 1965 shortbed fleet great granddads. Been told im nuts to bring it back from the dead (still going to happen) plans-all stock with a turbo 292 inline 3 speed column shift. and thats it big block 427 and 5 speed trans and ford 9 inch theyhave no home yet thinking what to put them in and a 79 c60 trash truck um no idea i have one

03-20-2007, 01:06 AM	#5
Pyrotechnic Registered User Join Date: Feb 2007 Location: Austin, TX Posts: 3,930	Re: Rear end question The 2 rear ends dont have much if anything in common besides the 10 bolts. The best bet if you want to go all out with gears and posi is to find a used 12 bolt and have it rebuilt with the gears and posi unit you want. You could do this with the 10 bolt but I personally wouldn't feel good about investing money in a 10 bolt as it's not as strong. If you only plan to run a stock 350 for street driving though, a 10 bolt is fine. Since you want to put in a posi and lower gears, it sounds like you want to go fast, so a 12 bolt would be the best option.

03-20-2007, 06:56 AM	#6
hiway Mad Scientist Join Date: Jul 2005 Location: Enola Arkansas Posts: 380	Re: Rear end question Not to mention the small 10 bolt from the car is very WEAK. __________________ Everythang relates to Beer! 86 1/2ton on tons! sbc/465/208/D60/14/35's 81 Postal....with 468 bbc 97 Merc Marq comuter 07 Suburban 02 Danger Ranger

03-20-2007, 11:34 AM	#7
Srubydo1986 The Crazy Machanic Join Date: Jan 2007 Location: Nokesville Va Posts: 1,437	Re: Rear end question I dont know why people dont like the chevy 10 bolt , like an unwanted red head step child. My chevelle has a 10 bolt and when the car was running I drove the car like a race car (speed scares me but 100 in the car) mud truck Got stuck in a car show just hit the gas a through some mud) and a rally car (lot of gravel roads around here 85 most of the time and drifting corners). Just my 2 cent all my 10 bolt have dont very well except for the one in my old 86 c10 the rod in the main case bored to hole from being round to oval. But that can happen in a 12 bolt to. __________________ 1986 Sliverado longbed 400 small block mean as hell, 700r4 trans (5 speed coming one day) 1970 chevelle 2dr sedan Latest update June 24 2007. *1957 4 door stationwagon - pink all original needing a good restore (body great, floors bad) newest additions 1965 shortbed fleet great granddads. Been told im nuts to bring it back from the dead (still going to happen) plans-all stock with a turbo 292 inline 3 speed column shift. and thats it big block 427 and 5 speed trans and ford 9 inch theyhave no home yet thinking what to put them in and a 79 c60 trash truck um no idea i have one

03-20-2007, 12:49 PM	#8
bent The master of disaster Join Date: Nov 2006 Location: Warsaw Texas Posts: 249	Re: Rear end question So is their any rear end that you can slide into place and have posi i know 10 bolts are ok because i had a 82 long bed that was a 10 bolt posi and i beat the crap outta it but all asideis their any rear end that will fit my 80 chevy long wide 1/2 ton

03-21-2007, 01:07 AM	#10
crm318 Alright Alright Alright Join Date: Mar 2004 Location: Midland, Texas Posts: 1,672	Re: Rear end question something else to think about: i had a 71 cutlass with a 10 bolt rear and i bought it a posi from an 80s half ton truck. it had a 31 spline axle and the car 10 bolt had a 28 spline axle. i dont think that the car and truck posi are compatable because of that reason. __________________ 1972 Cheyenne Chevrolet red and white 357ci, Vortec heads, GM Performance high rise intake, Comp 268H .454/.454 218/218 110 LSA Quadrajet carb, Flowtech headers, 2.25 40 series HEI, Curve kit, TH 350, 3.07 gears 275/60/15s on 15x8 rallies



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