| FAQ |
| Members List |
| Social Groups |
| Calendar |
| Search |
| Today's Posts |
|
#1
08-15-2020, 02:38 PM
|
||||
|
||||
12 bolt open to posi carrier install question
My son has a 72 455 lemans. A few years back we bought a 12 bolt open rear out of a 70 GP and installed it. I didn’t know they even made a 12 bolt open but they do. Now he was to swap in a Eaton posi. If the existing open carrier and the posi are both 3 series carriers can we swap the same ring gear and install the new posi using the same Shims without redoing the pinion crush deal, setting backlash etc? Thanks
|
|
#2
08-15-2020, 03:01 PM
|
||||
|
||||
|
The ring gear will swap right over and you can leave the pinion and reuse all the previous shims as a starting point. Once its assembled you'll need to make sure backlash and bearing preload is correct. If it is then you need to check the contact pattern. If backlash or preload is out of spec or contact pattern isn't good you'll need to adjust your shims accordingly.
__________________
1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
|
#3
08-15-2020, 03:09 PM
|
||||
|
||||
|
Shouldn’t the carrier dimensions be the same and the shims should be correct? Do carrier dimensions vary?
|
|
#4
08-15-2020, 03:12 PM
|
||||
|
||||
|
Quote:
__________________
1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
|
#5
08-15-2020, 07:11 PM
|
||||
|
||||
|
Quote:
__________________
1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
| The Following User Says Thank You to AG For This Useful Post: | ||
|
#6
08-15-2020, 07:41 PM
|
||||
|
||||
|
Thinking the same thing that the pinion can stay in place without being touched. The pinion shims make up for the difference in manufacturing tolerances to set pinion depth to carrier center line which varies with each axle housing. If the pinion depth was correct before it will remain correct since the same pinion and ring gear are being transferred over.
Backlash which is determined by the side to side fit of the carrier will most likely be different. I've installed new bearings on the carrier and had to change shims to get the backlash where it needed to be.
__________________
Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon. |
| The Following User Says Thank You to lust4speed For This Useful Post: | ||
|
#7
08-16-2020, 12:00 AM
|
|||
|
|||
|
MEASURE THE BACKLASH before you take the "open" carrier out.
Put the new "posi" carrier back in with the proper preload, and match the new backlash to the old. |
|
#8
08-16-2020, 08:27 AM
|
||||
|
||||
|
Good info. Thanks!
|
|
#9
08-16-2020, 01:23 PM
|
|||
|
|||
|
Quote:
__________________
 466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2 373 gears 3200 Continental Convertor best et 10.679/127.5/1.533 60ft 308 gears best et 10.76/125.64/1.5471 |
| Reply |
|
|
The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.
Linear Mode
