Open 3.07 to posi series questions.

[firefighterchevy]

Well, the internet is full of great advice...just sometimes confusing and sometimes incorrect. I hope to gain some simple answers and knowledge from you folks who know this stuff best. So, this is my plan: I have a 69 C10 that currently has an open 3.07 rear axle. I have a 3.73 posi I bought that came from a 69 C10 also.
First off, I have nothing against 3.73 gears, in fact, I have them in all my other pickups and Suburban. I just don't want them in this pickup, as I would like to keep some MPG and top end speed at lower RPM's.
As far as I can tell by reading all over, the 3.07 is a Series 3 setup. I have read various places conflicting info on the 3.73, as to it may be a Series 3 or a Series 4.
What I want to do is stay with 3.07 gears, but make it posi. Can I take the 3.73 carrier and put the 3.07 gears on it and install it in my 3.07 axle housing? Am I going to need a gear shim if I can? Will this even fit/work? I am already aware of setting up the bearings with the swap, if I can. Can some of you folks point me in the right direction? Let me know if I forgot some info that may be needed, and I did a search and couldn't find a thread like this here. Thanks.

[67 chevelle]

To my knowledge , 3.73 gears go on a 3 series posi , so should a 3.07 , 3.73 will not work on a 4 series posi ,, I have a 4 series sitting in my garage ,, where it has been for many years because of this very issue ,,, expensive mistake

[NYroadRat]

Confirming that you can use your 3 series carrier with any 3 series gears. In short, put your 3.07 ring gear on your 3.73 posi's carrier and you're done.

[hugger6933]

Welcome to the board first off Now the "some" 3:73 gears being 4 series gear sets is a real thing but not from the General. Those are made, if not mistaken, by gear makers to help some of the hot rodders with the issue your having but with deeper gear sets. All of the "3" gear should most def fit the posi unit for the 3 gears.
Now that that is clear as mud anything else I can clear up for you? Jim

[firefighterchevy]

Thanks, I appreciate the input and clarification. This will make the project swap easy and reasonable since I already have everything.

[Fitz]

Originally Posted by firefighterchevy

Well, the internet is full of great advice...just sometimes confusing and sometimes incorrect. I hope to gain some simple answers and knowledge from you folks who know this stuff best. So, this is my plan: I have a 69 C10 that currently has an open 3.07 rear axle. I have a 3.73 posi I bought that came from a 69 C10 also.
First off, I have nothing against 3.73 gears, in fact, I have them in all my other pickups and Suburban. I just don't want them in this pickup, as I would like to keep some MPG and top end speed at lower RPM's.
As far as I can tell by reading all over, the 3.07 is a Series 3 setup. I have read various places conflicting info on the 3.73, as to it may be a Series 3 or a Series 4.
What I want to do is stay with 3.07 gears, but make it posi. Can I take the 3.73 carrier and put the 3.07 gears on it and install it in my 3.07 axle housing? Am I going to need a gear shim if I can? Will this even fit/work? I am already aware of setting up the bearings with the swap, if I can. Can some of you folks point me in the right direction? Let me know if I forgot some info that may be needed, and I did a search and couldn't find a thread like this here. Thanks.

2.72 through 3.42 use the series 3 carrier. 3.73 and up use the series 4. Your 3.07 gears will not fit a series 4 carrier.

[Fitz]

Originally Posted by firefighterchevy

Well, the internet is full of great advice...just sometimes confusing and sometimes incorrect. I hope to gain some simple answers and knowledge from you folks who know this stuff best. So, this is my plan: I have a 69 C10 that currently has an open 3.07 rear axle. I have a 3.73 posi I bought that came from a 69 C10 also.
First off, I have nothing against 3.73 gears, in fact, I have them in all my other pickups and Suburban. I just don't want them in this pickup, as I would like to keep some MPG and top end speed at lower RPM's.
As far as I can tell by reading all over, the 3.07 is a Series 3 setup. I have read various places conflicting info on the 3.73, as to it may be a Series 3 or a Series 4.
What I want to do is stay with 3.07 gears, but make it posi. Can I take the 3.73 carrier and put the 3.07 gears on it and install it in my 3.07 axle housing? Am I going to need a gear shim if I can? Will this even fit/work? I am already aware of setting up the bearings with the swap, if I can. Can some of you folks point me in the right direction? Let me know if I forgot some info that may be needed, and I did a search and couldn't find a thread like this here. Thanks.

2.73 through 3.42 gearsets fit a series 3 carrier. 3.73 and up fit a series 4 carrier. Your 3.07 gears will not work with a series 4 carrier, but don't take my word for it. Go here: http://www.drivetrainspecialists.com...ed19587-1.html

[Fitz]

00

[frankslagoon]

Originally Posted by fitz

2.72 through 3.42 use the series 3 carrier. 3.73 and up use the series 4. Your 3.07 gears will not fit a series 4 carrier.

x2

[cdowns]

me i'd use that 373 posi and at the same time i'd dump the tranny and go for the extra gear and convienence of the 700-04 tranny

[Mike C]

Yup. Those other guys are correct. In the passenger car axle you can run up to 3.90's on the 3 series carrier, but in the truck the 3.73 is the 4 series carrier. Who knows why GM didn't just use the car version of the axle in everything, but they didn't.