Question on 68-72 Olds type "O" Rear

joe huestis · 11-13-2012, 08:42 PM

when changing gear ratio in this type differential, do you need to change carriers like you do in a "C" type 12 bolt ? this is the 12 bolt cover with the 10 bolt ring gear. changing gear from a 3:42 to a 4:33. thanks !

Dan Lattimore · 11-14-2012, 12:55 AM

Quote:

Originally Posted by joe huestis

when changing gear ratio in this type differential, do you need to change carriers like you do in a "C" type 12 bolt ? this is the 12 bolt cover with the 10 bolt ring gear. changing gear from a 3:42 to a 4:33. thanks !

Joe, Same case they just made the ring gears really thick.

rallye bob · 11-14-2012, 07:30 AM

Joe;
I went from a 3:23 to a 4:66 (GM gears) in the "O" rear.... in my '70 f/85...

Run to Rund · 11-14-2012, 11:54 AM

With OEM stuff, Olds parts had the same carrier for all "heavy duty" ratios, 3.42 to 5.00. The rear was used from late 1966 to 1970. The HD stuff wasn't readily available until 68; in 69 Olds went from 31 spline axles to 28 so the carrier side gears changed, of course.

BobD · 11-15-2012, 12:45 AM

Glad to see this post! This is going to be interesting...

joe huestis · 11-15-2012, 05:48 PM

Thanks for all your responses. Danny, we are going to move forward on this project a little at a time. Fred installed a line-loc and drag shocks this past weekend. The gears are next. We are seeing how much we need to do to run a tad below the E/Pure Stk. index without drastically altering this pristine all origional muscle car. Only 13K origional miles on odometer !
Bob, I am anxious to see this through, I believe car has potential. When Fred had it at Piedmont last weekend, I was amazed at the folks coming over to check his car out. They walked right past mine and didn't bother ! LOL !!

Dan Lattimore · 11-15-2012, 06:52 PM

Wow ! 13,000 miles ! Are you boys sure you want to do this ?

joe huestis · 11-15-2012, 07:14 PM

Fred will not do anything to devalue this car. Better to have some fun with it rather than it sit in a garage to just look at.

Mark Yacavone · 11-15-2012, 08:56 PM

Fred Rice · 11-17-2012, 10:32 PM

Well it looks like I have procured a ring and pinion set.....

(picture for Mark...lol)

My question is ....as these are original GM pieces, will they fit the 3:42 carrier that is in the car now? I have 31 spline axles. I have heard of a spacer being needed on some of these applications.Would I need a spacer with a factory set of gears vs. aftermarket or visa versa? Just want to make sure before we dig into this..Any help on this will be appreciated.

Regards,
Fred

11-13-2012, 08:42 PM	#1
joe huestis Senior Member Join Date: May 2006 Location: Youngsville, N.C. Posts: 621 Likes: 279 Liked 393 Times in 111 Posts	Question on 68-72 Olds type "O" Rear when changing gear ratio in this type differential, do you need to change carriers like you do in a "C" type 12 bolt ? this is the 12 bolt cover with the 10 bolt ring gear. changing gear from a 3:42 to a 4:33. thanks ! __________________ Joe Huestis "Annie's Song" Racing U/SA 2724 Youngsville, NC

11-14-2012, 07:30 AM	#3
rallye bob Member Join Date: Sep 2006 Location: Genoa, Illinois Posts: 488 Likes: 9 Liked 6 Times in 4 Posts	Re: Question on 68-72 Olds type "O" Rear Joe; I went from a 3:23 to a 4:66 (GM gears) in the "O" rear.... in my '70 f/85...

11-14-2012, 11:54 AM	#4
Run to Rund Senior Member Join Date: Sep 2007 Location: Henderson, NV Posts: 583 Likes: 8 Liked 54 Times in 27 Posts	Re: Question on 68-72 Olds type "O" Rear With OEM stuff, Olds parts had the same carrier for all "heavy duty" ratios, 3.42 to 5.00. The rear was used from late 1966 to 1970. The HD stuff wasn't readily available until 68; in 69 Olds went from 31 spline axles to 28 so the carrier side gears changed, of course.

11-15-2012, 12:45 AM	#5
BobD Junior Member Join Date: Feb 2006 Location: Wake Forest, NC Posts: 41 Likes: 11 Liked 0 Times in 0 Posts	Re: Question on 68-72 Olds type "O" Rear Glad to see this post! This is going to be interesting...

11-15-2012, 05:48 PM	#6
joe huestis Senior Member Join Date: May 2006 Location: Youngsville, N.C. Posts: 621 Likes: 279 Liked 393 Times in 111 Posts	Re: Question on 68-72 Olds type "O" Rear Thanks for all your responses. Danny, we are going to move forward on this project a little at a time. Fred installed a line-loc and drag shocks this past weekend. The gears are next. We are seeing how much we need to do to run a tad below the E/Pure Stk. index without drastically altering this pristine all origional muscle car. Only 13K origional miles on odometer ! Bob, I am anxious to see this through, I believe car has potential. When Fred had it at Piedmont last weekend, I was amazed at the folks coming over to check his car out. They walked right past mine and didn't bother ! LOL !! __________________ Joe Huestis "Annie's Song" Racing U/SA 2724 Youngsville, NC

11-15-2012, 06:52 PM	#7
Dan Lattimore Member Join Date: Jan 2003 Location: Beaverdam, Va./ Port St. Lucie,Fla. Posts: 362 Likes: 177 Liked 154 Times in 37 Posts	Re: Question on 68-72 Olds type "O" Rear Wow ! 13,000 miles ! Are you boys sure you want to do this ? __________________ 66W30POST

11-15-2012, 07:14 PM	#8
joe huestis Senior Member Join Date: May 2006 Location: Youngsville, N.C. Posts: 621 Likes: 279 Liked 393 Times in 111 Posts	Re: Question on 68-72 Olds type "O" Rear Fred will not do anything to devalue this car. Better to have some fun with it rather than it sit in a garage to just look at. __________________ Joe Huestis "Annie's Song" Racing U/SA 2724 Youngsville, NC

11-15-2012, 08:56 PM	#9
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,742 Likes: 2,845 Liked 5,002 Times in 1,902 Posts	Re: Question on 68-72 Olds type "O" Rear __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

11-17-2012, 10:32 PM	#10
Fred Rice Junior Member Join Date: May 2008 Location: Cary, NC & Lake Gaston, Va. Posts: 24 Likes: 0 Liked 0 Times in 0 Posts	Re: Question on 68-72 Olds type "O" Rear Well it looks like I have procured a ring and pinion set..... (picture for Mark...lol) My question is ....as these are original GM pieces, will they fit the 3:42 carrier that is in the car now? I have 31 spline axles. I have heard of a spacer being needed on some of these applications.Would I need a spacer with a factory set of gears vs. aftermarket or visa versa? Just want to make sure before we dig into this..Any help on this will be appreciated. Regards, Fred Last edited by Fred Rice; 11-17-2012 at 10:49 PM.