I understand that the 67 rearend is 1" shorter than the later model rearends. Can I use a 69 Chevelle 12-bolt under my 67? If so, what all do I need to be concerned about? Will I have to get wheels with specific back spacing? Thanks!

The '69 Chevelle rear end will work. Your wheels will be 1/2 inch farther out on each side. Everything else will be the same.

As Freddie mentioned, your wheels will be spaced out only slightly more.
First, if you have access to a 68-72 12bolt-------------GET IT, BOLT IT IN!!!!!!!!!!!!
Once installed, then check for wheel/tire clearance and go from there. With stock wheels and a reasonable width tire, you should be fine. With aftermarket/custom wheels and tires, it will simply be a matter of checking to see what will/will not fit and clear. Inside clearance will not be an issue. The possible clearance issues will be between the outside sidewall of the tires and the wheel opening. If you end up with 1/2in-3/4in clearance, that will be adequate.
On my 70, I have 15x8 Corvette Ralley wheels and 255/60R15 tires and 1/4in-1/2in clearance and the tire sidewall has never touched the wheel opening. :thumbsup:

Thanks for the responses!!! I believe I'll rebuild the 69 12-bolt to match the engine combo I have and bolt it on.

I'm going to be running a 402 4-bolt main, not sure of the HP, and a Muncie M20. What would be a good street gear? I was thinking 3.73.

If you will be staying in town the the 3.73 will be fine. If you want to get out on the highway much then you might want a 3.42. I recommend that you find a RPM calculator and check the RPMs at different speeds with different gear ratios and tire diameters.

Thanks for the responses!!! I believe I'll rebuild the 69 12-bolt to match the engine combo I have and bolt it on.

I'm going to be running a 402 4-bolt main, not sure of the HP, and a Muncie M20. What would be a good street gear? I was thinking 3.73.


Almost sounds like you're building my car! Except mine's a '66, otherwise another M-20, with a '70 12-bolt and 3.73 gears. I currently have a set of 255 tires on rally wheels and they fit the wheel wells with room to spare. Unfortunately it'll be a while before I'm driving this, so I don't have direct experience with it yet, but I would have preferred a taller gear ratio. Decades ago, I drove a '64 GTO with an M-20 and 3.23 gears, and really liked that combination for general street driving. If you're looking for more performance, the 3.42s would probably be better. I think the 3.73s will be okay, but I'd personally rather trade off a little bit of first gear performance to get lower RPMs on the freeway.

Just my .02.

Sounds like the 3.42 may be the way to go, do some cuise-ins that are 30 to 60 miles out.

If you will be staying in town the the 3.73 will be fine. If you want to get out on the highway much then you might want a 3.42. I recommend that you find a RPM calculator and check the RPMs at different speeds with different gear ratios and tire diameters.

Here's one on my site

http://www.chevellestuff.com/tools/rpm_calculator.htm

FWIW I ran a later/wider rear in my 67 for a number of years with no problems. The only concern is the wheel backspacing and overall tire width is a bit more limited and needs to be considered.

here is a good one for you >>>
went to put new axles in my 67ss396 12b posi last year (factory differential)....
the date code on the rear end was june 12, 1967....
guess what ? it took the longer axles instead of the shorter version..
with 67's they used what was around at the time at assembly so don't bet on anything when doing repairs/modifications....
I run 15x8 corvette rallys with 235-60615 tires and no clearance issues...

It's been reported that late 67s used the later wide style rear ends. I've never seen one that I can recall but they've been reported. Can you find the stamping on the axle tube along with the casting date and exact casting numbers/letters, e.g. X NF3917124 or 3917124NF, etc.? Is June 12 the stamped assembly date or the casting date? What plant built your Chevelle and what's it's body date?

I'm not sure I'd go so far as to say "...with 67's they used what was around at the time at assembly..." as they normally didn't just install whatever they had on hand without some sort of thought behind it. The rear end assembly, like the engine and transmission, were coded on the POP before assembly ever began - workers didn't just pull anything off the shelf.

Thanks for the responses!!! I believe I'll rebuild the 69 12-bolt to match the engine combo I have and bolt it on.

I'm going to be running a 402 4-bolt main, not sure of the HP, and a Muncie M20. What would be a good street gear? I was thinking 3.73.

I have a healthy .030 over SB400 in the 70 with the 3.07 posi and M20. The motor has plenty of torque from a dead stop to compensate for the 3.07 ratio (and your 402BB should be even stronger), although it's not a rocket off the line at the strip (and the ONLY strip time is at Chevellabration). Once I get rolling (10-15mph), it's gone because it winds forever in 1st-2nd gears. But for all around driving, I have ZERO interest in swapping to a lower gear ratio. City cruising is just fine (some people have a problem driving their car in 1st or 2nd gear as slower speeds, not me), and you just can't beat the lower rpm's on the Interstate with the 3.07 rear.

dale, I had all of of those numbers written down and checked it out last year. I never found a stamp on my axle tubes but looked very hard for it. this was a casting date I found in the housing. it and the NFxxxx checked out to be correct for '67. this is a late build car from the atl plant. it still had the original gm 3.55 gears in the posi diff. crazy car came with 396/325, snorkel type air cleaner, floor shift/console powerglide, no gages or factory tach, a/c, pdb (with the leaky calipers) and power steering. my friends just say it was a fast "chick" car when it was purchased new....ha...
sure nuff when I took out the axles it had the original long version (30.063 lg). glad I measured before ordering !!
now the car is the way I want it >....3.42 rear, 700r4, 496/600hp....still have all of the original stuff in a storage shed though....

Pulled the carrier, here is the casting # EDB-80140, can someone tell me which series this is?

Doesn't ring a bell. Photo?

The EDB-80140 could be EDB-30140, kind of hard to tell.

30140 is the Eaton 3 series carrier.

That is a Eaton 3 series posi. Good stuff! Tom