#1  
Old 04-13-2022, 08:01 PM
prostreet64's Avatar
prostreet64 prostreet64 is offline
Ultimate Warrior
 
Join Date: Jul 2007
Location: Gainesville, Fl.
Posts: 1,324
Default 28 spline to 30 spline carrier

Can you convert an Eaton Posi carrier, 28 spline to a 30 spline by just changing out the side gears to 30 spline? I want to upgrade my axles to 30 spline but don't want to buy a whole new carrier. I have heard that this can be done but then I read some other articles that say no.

__________________
69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car.

79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads,Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.72 @ 126 so far... no tuning yet.
  #2  
Old 04-14-2022, 03:32 PM
Skip Fix's Avatar
Skip Fix Skip Fix is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Katy,TX USA
Posts: 20,541
Default

8.5 10 bolt Eaton-yes. Just spider swap I think. Factory S spring carrier not sure. Tom's Differentials has the 30 spline spiders.

__________________
Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
The Following User Says Thank You to Skip Fix For This Useful Post:
  #3  
Old 04-14-2022, 05:52 PM
prostreet64's Avatar
prostreet64 prostreet64 is offline
Ultimate Warrior
 
Join Date: Jul 2007
Location: Gainesville, Fl.
Posts: 1,324
Default

Skip, thanks for the input. I do have the 8.5, 10 bolt Eaton unit.

__________________
69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car.

79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads,Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.72 @ 126 so far... no tuning yet.
  #4  
Old 04-14-2022, 07:33 PM
Skip Fix's Avatar
Skip Fix Skip Fix is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Katy,TX USA
Posts: 20,541
Default

I have the 28 spline I pulled out of the 78 for a 30 spline and am going to try an put 30s in it to put in my 97 Chevy truck in place of the "Gov Lok" POS.

Tom's of Tom's Differentials passed away a couple of years ago but I think the family is still selling parts. He had a cool 12 bolt conversion for 63-81 Corvette pumpkin IRS.

__________________
Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
The Following User Says Thank You to Skip Fix For This Useful Post:
  #5  
Old 04-25-2022, 05:37 PM
cgeise's Avatar
cgeise cgeise is offline
Ultimate Warrior
 
Join Date: Jan 2005
Location: Ellensburg,WA
Posts: 2,938
Default

If I remember right, and sometimes I dont --- I think the 30 spline spiders out of a 12 bolt will go right in that 10 bolt.

  #6  
Old 04-25-2022, 06:31 PM
'ol Pinion head 'ol Pinion head is offline
Ultimate Warrior
 
Join Date: Apr 2000
Location: INJUN Territory, Red State Merica!
Posts: 9,564
Default

30 spline axles won't fit through the machined ends for the carrier bearings on a 28 spline posi carrier. Wouldn't want to machine the carrier ends to make them larger inside as it would weaken the carrier.

When one goes to a 30 spline carrier in a prev 28 spline equipped housing, there is a different carrier bearing & race combo one has to use to make it fit. Have posted the part numbers before, search function...

__________________
Buzzards gotta eat... same as worms.
The Following User Says Thank You to 'ol Pinion head For This Useful Post:
  #7  
Old 04-26-2022, 07:29 AM
AG's Avatar
AG AG is offline
Ultimate Warrior
 
Join Date: Feb 2000
Location: NH
Posts: 3,240
Default

Just to be clear, 30 spline axles will not fit in an original 28 spline carrier whether it's stock or an Eaton?

__________________
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.
  #8  
Old 04-26-2022, 07:34 AM
Cliff R's Avatar
Cliff R Cliff R is offline
Ultimate Warrior
 
Join Date: Nov 2000
Location: Mount Vernon, Ohio 43050
Posts: 17,972
Default

"I have the 28 spline I pulled out of the 78 for a 30 spline and am going to try an put 30s in it to put in my 97 Chevy truck in place of the "Gov Lok" POS."

Skip, were you out doing "hole shots" with your truck again?

The Eaton locking differentials are excellent......for what they were designed for. There are millions of them in use w/o issue. Even with that said they do NOT like any type of "shock" load and I've seen a good many with busted up governors and other items in them over the years.

A good friend of mines son bought a HD GMC 2500 a couple of years ago, low miles and in mint condition. The boy couldn't wait to go out and have some "fun" with it. He was "whacking" it pretty hard at every stop he came to. The roads were slippery with some wet/icy patches here and there. He'd get one wheel spinning really hard then the locker would engage and "bark" the tire on the better surface. That fun night got expensive pretty quick when he EXPLODED the carrier and it literally fell out of the diff in about 20 pieces! I doubt if one would last more than a couple of dozen runs in a full drag racing application behind a stout Pontiac engine..........

__________________
If you can read this, thank a teacher. If you can read this in English, thank a Veteran!
https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
  #9  
Old 04-27-2022, 09:01 AM
Skip Fix's Avatar
Skip Fix Skip Fix is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Katy,TX USA
Posts: 20,541
Default

No Cliff but it is getting a 383 Vortec motor. The dog says his truck needs a little pep! The freaking new truck barely have enough room in the passenger footwell for 1 bag of groceries much less a Doberman like the room "Old Red" has

High school buddy with his stick 6 cylinder Challenger and Air shocks went around a turn doing the same thing your friend's son did and blew out the spiders! but with the stick big tires a glass pack and a tunnel ram scoop on the hood he bluffed a lot of folks down

Roger is correct the newer Eaton carriers take a different bearing to fit in the old housings.

__________________
Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
The Following User Says Thank You to Skip Fix For This Useful Post:
  #10  
Old 04-27-2022, 03:33 PM
prostreet64's Avatar
prostreet64 prostreet64 is offline
Ultimate Warrior
 
Join Date: Jul 2007
Location: Gainesville, Fl.
Posts: 1,324
Default

For you guys in the know can you verify that the stock (8.5 corporate) rear end axle housing is 55.25" for my 79 Trans Am? and if the pinion offset is 1/2 ". And also do you know if the brake register is 2.78"? Trying to make sure I get the right axles and other parts needed for converting from 28 to 30 spline carrier. Thanks

__________________
69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car.

79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads,Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.72 @ 126 so far... no tuning yet.

Last edited by prostreet64; 04-27-2022 at 03:39 PM.
  #11  
Old 04-27-2022, 07:33 PM
Skip Fix's Avatar
Skip Fix Skip Fix is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Katy,TX USA
Posts: 20,541
Default

The brake pilot is 2.78. If going rear discs the thicker rotor often does not allow a "Hubcentric" wheel to locate unless you get custom longer ones-Dutchman can do that Moser will laugh at you. 0.700-0.750 long is what a factory 79-81 rear disc pilot length is. Not sure why they would need pinion offset to make axles. Some do want the axle flange to wheel flange dimension my '81 I had 2.75" . Total length 30 1/8 long axles. Be sure they know they are 10 bolt if using C clips as some will use a 12 bolt which has a thicker "Button" on the axle.

__________________
Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
The Following User Says Thank You to Skip Fix For This Useful Post:
  #12  
Old 04-28-2022, 08:02 AM
prostreet64's Avatar
prostreet64 prostreet64 is offline
Ultimate Warrior
 
Join Date: Jul 2007
Location: Gainesville, Fl.
Posts: 1,324
Default

Skip, thanks for the info. I am keeping the rear drum setup and will be using c-clip eliminators. The shop that will be doing the work is getting the axles and all the other parts needed from Strange. I would have thought that Strange would know the measurements for a stock 8.5, 10 bolt rear end. I guess they want to have everything measured to be absolutely sure.

__________________
69 Bird w/1970 400 block(409 cubes), #64 heads, hyd. roller, Q-jet by Jeff E., original interior, ps, pdb, th350, and 3.73 gears. Pump gas, street driven muscle. 3800 lbs. race weight. Best, 11.39 @118, my son's car.

79 T/A w/463, Scat crank, Eagle rods, Icon pistons, Lunati solid roller, 262/270, KRE 325 heads,Northwind intake, QF950 carb, full interior, ps, pdb, th350, and 3.73 gears. Pump gas, 3650 lbs. race weight. 10.72 @ 126 so far... no tuning yet.
  #13  
Old 04-28-2022, 04:43 PM
Skip Fix's Avatar
Skip Fix Skip Fix is offline
Ultimate Warrior
 
Join Date: Dec 1999
Location: Katy,TX USA
Posts: 20,541
Default

Dutchman and Moser have the stock specs and off the shelf 10 bolt axles in 30 spline

__________________
Skip Fix
1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever!
1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand
1965 GTO 4 barrel 3 speed project
2004 GTO Pulse Red stock motor computer tune 13.43@103.4
1964 Impala SS 409/470ci 600 HP stroker project
1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 09:18 AM.

 

About Us

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.

 




Copyright © 2017