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#1 |
Registered User
Join Date: Sep 2010
Location: Winchester Oregon, formerly Vancouver BC
Posts: 2,949
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POSI Question
Will a 30 spline carrier and gear set from a 66 chevy truk 12 bolt fit in my 72 12 bolt in my suburban. I want to re-gear the rear from 3:08 to 3:73 and know I can do a thick cut ring and pinion or change the carrier, just don't know if the rears are the same.
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#2 |
Registered User
Join Date: Aug 2011
Location: Tahlequah, Ok
Posts: 1,235
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Re: POSI Question
Ring gear/pinion and the carrier are interchangable on GM 12 bolt trucks from 65 all the way up thru the 80's. I have changed my old trucks over to 3:40's from 70's and 80's 12 bolts.... no problems. Be sure and change the carrier also ( as you stated ) since there are different thickness of ring gears between gear ratios. Mr Gasket also makes a ring gear spacer ( which I have also used before ) that includes longer bolts if you didn't have the correct carrier
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1965 long bed ( grandpas old truck ) 1964 long bed BBW Custom Cab 1966 Short stepside 1964 long bed 1965 long bed Custom Cab, factory air, V-8, powerglide |
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#3 |
Registered User
Join Date: Dec 2009
Location: Orlando, FL
Posts: 131
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Re: POSI Question
do you have the 3.08 POSI carrier?
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#4 |
Registered User
Join Date: Sep 2010
Location: Winchester Oregon, formerly Vancouver BC
Posts: 2,949
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Re: POSI Question
I do have a posi carrier now with 3:08 gears but have a 700R4 so my motor lugs at freeway speed.
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#5 |
Registered User
Join Date: Dec 2009
Location: Orlando, FL
Posts: 131
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Re: POSI Question
I have the posi with 3.73 's and i wanted to go 3.08. Id have to double check everything when i go to the shop next sunday but maybe we could work something out.
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#6 |
Rollin' Old Skool
Join Date: Jun 2007
Location: Hattiesburg, MS
Posts: 5,371
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Re: POSI Question
interesting...this came up in the thread recently regarding a 700R4 swap...i had mentioned being interested in doing the swap as well...however, about a year or so ago we refreshened & swapped a '72 rear with 3.08's into my '66 C-10, which has a Powerglide currently....the idea at the time was to help with highway driving....so, does this mean i'm gonna have to switch to a different gear set in order to freeway/highway drive with the 700r4?
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_____________________________________________ Phillip My Build threads: 1966 Chevy C-10 "Black Betty" shortbed, fleetside, BBW, 327 V8/ Powerglide (under construction) http://67-72chevytrucks.com/vboard/s...ighlight=betty 1997 Chevy Tahoe, 2dr/2wd, mild custom (Daily driver) http://67-72chevytrucks.com/vboard/s...d.php?t=601142 Pics: '66 C-10 https://flic.kr/s/aHsjHWD4h9 '97 Tahoe https://flic.kr/s/aHsjGZ7wKP '93 C-1500 https://flic.kr/s/aHskxdpdnQ '88 S-10 Blazer https://flic.kr/s/aHsjYGx4Md Previous Rides: 1993 Chevy S-10 ext. cab, 4.3L, 4/5 drop (Sold) 1993 Chevy C-1500 short/step Retro-Rod (Sold) 1988 S-10 Blazer 2dr/2wd mild custom (Sold) |
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#7 |
Registered User
Join Date: Sep 2010
Location: Winchester Oregon, formerly Vancouver BC
Posts: 2,949
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Re: POSI Question
I have fuel injected motor in my truck and it does pretty good at 19MPG but I have to cruise at 73 on the freeway to do 1900 RPM. I have 31" tires and I can watch my vacuum gauge and when I need to accelerate at 65 it really drops into the power mode to accelerate, yet if I drop down to 3rd it stays in the green when I need to speed up. It is all about tire and gearing and I think I can actually improve my performance and mileage by increasing cruising rpm's. I only turn 1400 RPM at 65.
I would do the swap but I will use this posi and gear set for my powerglide truck as it is an open carrier, thanks though. |
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#8 |
60-66 Nut
![]() ![]() Join Date: Mar 2007
Location: Coeur d'Alene, Idaho
Posts: 23,246
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Re: POSI Question
Yep, that is a common misconception that lower rpm's means better mpg's. Not always so. The engine needs to operate in it's power band to be efficient. IMO 3.73's or 3.42's are a ideal gears for use with a OD trans. But that also depends on tire diameter.
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Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE |
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#9 | |
Rollin' Old Skool
Join Date: Jun 2007
Location: Hattiesburg, MS
Posts: 5,371
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Re: POSI Question
Quote:
yeah, i've read that as well...and i've also read of a couple folks with a 700r4 w/ 3.08's....my truck has a 327, Edelbrock Performer intake, Edelbrock 600 carb, and otherwise pretty stock i think....current tires are 205/75/15, which is at 27.10 overall diameter
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_____________________________________________ Phillip My Build threads: 1966 Chevy C-10 "Black Betty" shortbed, fleetside, BBW, 327 V8/ Powerglide (under construction) http://67-72chevytrucks.com/vboard/s...ighlight=betty 1997 Chevy Tahoe, 2dr/2wd, mild custom (Daily driver) http://67-72chevytrucks.com/vboard/s...d.php?t=601142 Pics: '66 C-10 https://flic.kr/s/aHsjHWD4h9 '97 Tahoe https://flic.kr/s/aHsjGZ7wKP '93 C-1500 https://flic.kr/s/aHskxdpdnQ '88 S-10 Blazer https://flic.kr/s/aHsjYGx4Md Previous Rides: 1993 Chevy S-10 ext. cab, 4.3L, 4/5 drop (Sold) 1993 Chevy C-1500 short/step Retro-Rod (Sold) 1988 S-10 Blazer 2dr/2wd mild custom (Sold) |
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#10 |
Registered User
Join Date: Sep 2010
Location: Winchester Oregon, formerly Vancouver BC
Posts: 2,949
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Re: POSI Question
Well, I won the posi carrier and gear set from ebay so hopefully this really brings my truck to life.Looking at increased performance and maybe a big smoky burnout once in awhile.
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#11 | |
Registered User
![]() Join Date: Jul 2009
Location: Menifee, CA
Posts: 471
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Re: POSI Question
Quote:
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#12 |
Registered User
Join Date: Sep 2010
Location: Winchester Oregon, formerly Vancouver BC
Posts: 2,949
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Re: POSI Question
Yeah it really sucks because I am forced to always downshift, hopefully this helps with acceleration, mileage and driveability.
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#13 |
Registered User
Join Date: Oct 2010
Location: Gresham, Oregon
Posts: 93
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Re: POSI Question
My 64' Stepside I have 3.54's and a 700R4 and a goodwrencg gas 350 I get 18 to 20mpg on the freeway 15" tires runs right about 19 to 20 RPM's around town I drive in 3rd I love it
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#14 |
Registered User
Join Date: Jan 2010
Location: Regina, SK
Posts: 804
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Re: POSI Question
Did 3.54's come stock in these trucks? I always assumed my truck was 3.73 because that is the most common. Maybe i'll have to do a tooth count and check.
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#15 |
Registered User
![]() Join Date: Sep 2009
Location: menifee california
Posts: 788
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Re: POSI Question
3::54 were dana 44 found in the GMC
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#16 |
Registered User
Join Date: Feb 2008
Location: Sidney,b.c.
Posts: 4,425
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Re: POSI Question
http://www.billstruckshop.com/60-66used.html
has a 3.08 and a 3.73 posi listed for sale 1st column down ron |
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