73-77 Cutlass Posi Rearend
Car Farmer
Joined: May 2009
Posts: 100
From: McHenry County, IL
Is that the original series 2 carrier in there or the series 3 for the lower gears? I think the series 2 has a 726 stamped in it whereas the 3 has a 725. Do you happen to know what spline axles are in there, 28 or 30? Bolt in axles?
Registered User
Joined: Jul 2006
Posts: 1,826
From: Richfield, Oh
rear end info for you all
oK...
-1ST OFF gm 10 BOLT 8.5 DOES NOT HAVE A THICK GEAR SET...no such thing.
so that means it is a 3 series carrier OR it is set-up wrong!!! Oh Boy... lets hope all the correct parts are in there. as the pattern TO ME looks to be ok. FROM WHAT I can see.
-2nd gm never produced a 30 spline 8.5 bolt in axle rear.
so this rear is 28 spline BIA rear with stock BIA posi 726 (2 series) 725 (3 series) casting as stated in a earlier post.
30 SPLINE IS ONLY AFTERMARKET IN THE BIA SET-UP
IF you look on the back side of the carrier flange area deep in the webbing you will see a 7 2 5 or 7 2 6 one number in each web cavity so then you know what carrier these gears were installed on.
If they were installed on 726 carrier watch out...
IF YOU THINK 4.30 IS THICK YOU SHOULD SEE THE 5.57 RING...LOL
-1ST OFF gm 10 BOLT 8.5 DOES NOT HAVE A THICK GEAR SET...no such thing.
so that means it is a 3 series carrier OR it is set-up wrong!!! Oh Boy... lets hope all the correct parts are in there. as the pattern TO ME looks to be ok. FROM WHAT I can see.
-2nd gm never produced a 30 spline 8.5 bolt in axle rear.
so this rear is 28 spline BIA rear with stock BIA posi 726 (2 series) 725 (3 series) casting as stated in a earlier post.
30 SPLINE IS ONLY AFTERMARKET IN THE BIA SET-UP
IF you look on the back side of the carrier flange area deep in the webbing you will see a 7 2 5 or 7 2 6 one number in each web cavity so then you know what carrier these gears were installed on.
If they were installed on 726 carrier watch out...
IF YOU THINK 4.30 IS THICK YOU SHOULD SEE THE 5.57 RING...LOL
Car Farmer
Joined: May 2009
Posts: 100
From: McHenry County, IL
Although it could be wrong, I've found conflicting information on this various places on the web stating that some do have 30 splines depending on the year/application. Maybe it was geared to only C-clip types.
http://www.crankshaftcoalition.com/w...identification
A few months ago I had Bob Kelso from Rocket Racing build me a BIA 3.42 axle with a 725 carrier all from a 11/9/1973 date stamped rear end axle housing. The type 3 carrier and axles were original to it. From what I recall in our conversation, I want to say that it had a 30 spline axle in it because I remember asking and being surprised to hear that, but I could be wrong. I could pull the axle out and check the spline count on it. It's out of the car right now with no breaks assembled on it.
The gear in there has a Richmond part number on it and looks to be for a 4.10. I've never heard of a 4.30 for an 8.5 10 bolt.
I agree that this must be a type 3 carrier. Looking at Richmond's site, they don't offer gears for the type 2 that are thicker, as they do for the Chevy 12 bolt 8.875 rear.
http://www.crankshaftcoalition.com/w...identification
A few months ago I had Bob Kelso from Rocket Racing build me a BIA 3.42 axle with a 725 carrier all from a 11/9/1973 date stamped rear end axle housing. The type 3 carrier and axles were original to it. From what I recall in our conversation, I want to say that it had a 30 spline axle in it because I remember asking and being surprised to hear that, but I could be wrong. I could pull the axle out and check the spline count on it. It's out of the car right now with no breaks assembled on it.
The gear in there has a Richmond part number on it and looks to be for a 4.10. I've never heard of a 4.30 for an 8.5 10 bolt.
I agree that this must be a type 3 carrier. Looking at Richmond's site, they don't offer gears for the type 2 that are thicker, as they do for the Chevy 12 bolt 8.875 rear.
Registered User
Joined: May 2011
Posts: 3,688
From: Delta BC Canada
Fyi
Although it could be wrong, I've found conflicting information on this various places on the web stating that some do have 30 splines depending on the year/application. Maybe it was geared to only C-clip types.
http://www.crankshaftcoalition.com/w...identification
A few months ago I had Bob Kelso from Rocket Racing build me a BIA 3.42 axle with a 725 carrier all from a 11/9/1973 date stamped rear end axle housing. The type 3 carrier and axles were original to it. From what I recall in our conversation, I want to say that it had a 30 spline axle in it because I remember asking and being surprised to hear that, but I could be wrong. I could pull the axle out and check the spline count on it. It's out of the car right now with no breaks assembled on it.
The gear in there has a Richmond part number on it and looks to be for a 4.10. I've never heard of a 4.30 for an 8.5 10 bolt.
I agree that this must be a type 3 carrier. Looking at Richmond's site, they don't offer gears for the type 2 that are thicker, as they do for the Chevy 12 bolt 8.875 rear.
http://www.crankshaftcoalition.com/w...identification
A few months ago I had Bob Kelso from Rocket Racing build me a BIA 3.42 axle with a 725 carrier all from a 11/9/1973 date stamped rear end axle housing. The type 3 carrier and axles were original to it. From what I recall in our conversation, I want to say that it had a 30 spline axle in it because I remember asking and being surprised to hear that, but I could be wrong. I could pull the axle out and check the spline count on it. It's out of the car right now with no breaks assembled on it.
The gear in there has a Richmond part number on it and looks to be for a 4.10. I've never heard of a 4.30 for an 8.5 10 bolt.
I agree that this must be a type 3 carrier. Looking at Richmond's site, they don't offer gears for the type 2 that are thicker, as they do for the Chevy 12 bolt 8.875 rear.
I have owned two 1973 3.42 posi 10 bolt differentials. Both had bolt in axles & 28 splines.
Registered User
Joined: Jan 2008
Posts: 1,484
From: ENNIS TEXAS
For the record. The 8.5 only has a 2 series which is 2.41 -2.56 and a 3 series carrier. 2.73-----All the way... All 8.5 are 28 spline 1971-1989/90. In 1989/90 they switched to 30 spline on all to present.
Thread Starter
Registered User
Joined: Jan 2010
Posts: 634
From: Perryville, MO
Sorry guys, Im just getting back on here and never got any notifications that someone had responded.
I got this rear when I bought out 3 storage lockers from an individual a couple months back. He told me he had someone build this for one of his cars that he ended up selling before installing. So I know very little about what exactly was done to it. Everything inside looks nice, but I don't know much about rear ends.
You are correct on the gears, they are 4.10s. Im not sure where or why I thought they were 4.30s. As for as the carrier, I will pull the cover and check tomorrow when I get back home, weather permitting, and let everyone know.
I got this rear when I bought out 3 storage lockers from an individual a couple months back. He told me he had someone build this for one of his cars that he ended up selling before installing. So I know very little about what exactly was done to it. Everything inside looks nice, but I don't know much about rear ends.
You are correct on the gears, they are 4.10s. Im not sure where or why I thought they were 4.30s. As for as the carrier, I will pull the cover and check tomorrow when I get back home, weather permitting, and let everyone know.
Thread Starter
Registered User
Joined: Jan 2010
Posts: 634
From: Perryville, MO
It is a 726 posi unit. So, since it wasn't put together properly I guess I will be taking it apart and scrapping the housing. If anyone is interested in the gears or posi unit let me know. Not sure when Ill get around to taking it apart, but it will be on my to do list.
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