Joeg

Hi fellow Olds guys! I have a 1970 W-31 with a 12 bolt rear end. It has that style rear end that will only fit the 3:91 which I currently have. Or a 3:42 ratio. I am wondering where I can find the 3:42's at? Any info and advice would be greatly appreciated. I am obviously trying to shave some RPM's off with out the expense of a OD trans.

olds 307 and 403

I would contact Monzaz or 507Olds on here. You need original gears since the aftermarket gears are set up for the 3.08-3.23 carriers. Either that or a spacer would be needed or is it the Richmond gears need shaved? I still say they should have been designed to fit the 2.56-2.78 carrier since most cars have those ratios.

Fun71

Actually, that carrier will work with factory 3.42, 3.91, 4.33, 4.66, and 5.00 gear sets.

As stated above, you would need to find an original set of GM gears since no one makes 3.42s for the O-Type.

olds 307 and 403

Actually, Richmond does but for some reason the 3.08-3.23 carrier was chosen.

Fun71

I haven't seen Richmond 3.42 gears for many years. Good to know they are back in production as I have a '70 2.56 axle that could use an upgrade.

oldsmobiledave

Won't help you. They are for the 3.08-3.23 carrier

Fun71

Sure it would help me since I have a 671 carrier in a '68 O-Type. I'm just tired of the sealed bearings on that older rear and would like to get the '70 rear with the open bearing design set up for future use.

oldsmobiledave

You stated that you have a 70 2.56 that needed upgrading and you will agree that it won't work.

You made no mention of the 671 carrier. It will however work.

Fun71

Didn't think I needed to say much more than I wanted 3.42s instead of 2.56s in my '70 O-Type. How I get there from here wasn't the issue.

I have parts to work with:

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oldsmobiledave

I did not want novice olds owners to think that the Richmond 3.42 gear could be used in the 2.56 differential. A first time reader may have thought so from your original post.

Fun71

Good point, I hadn't thought of that.