3875745 is a 66 rear
3894939 is a 67 rear
3917124 is a late 67 -69 rear

Which one are you using?

 

Look on the front of the passenger side axle tube for the build code.
There is a casting date on one of the center section webs.

Post them here.

 

I found the code...3875745n.Going from the earlier post it appears it is the right rear end for my 66..Thank You,this will make getting the right offset a little less confusing:hurray:

 

As Mike noted...

3875745 - 66 rear
3894939 - 67 rear

These are the same width (just different spring mounting methods), the late 67 and later are wider and severly limit your standard wheel choices unless you use custom offsets.

And, FWIW, the casting numbers may have N, NF, X prefixes or suffixes. Haven't figured out EXACTLY what they mean for sure but it doesn't affect the width.

See my page at http://chevellestuff.net/qd/generic_rear_axle_info.htm for more generic information on Chevelle rear ends.

 

... the late 67 and later are wider ...

I do not believe that any 67 model year rear axle is any wider than any other 67 model year rear axle. The pumpkin casting number changed during 67 production (to the 3917124 that was also used in 68), but I have seen no evidence that the length of the axle tubes was changed before 68 production started.

This opinion is supported by the fact that there is one part number for a 66 12-bolt standard axle, a different part number for the first design 67 12-bolt standard axle, another different part number for the second design 67 12-bolt standard axle, and yet another different part number for 68 12-bolt standard axle.

If late 67 axles and 68 axles were the same, they would have the same part number ...

If someone has a 3917124 casting # axle with a build date indicating it was originally installed in a 67 Chevelle (rather than in an early 68) that measures as wide as a 68 rear, I'd like to see that, because I don't think such an animal exists! The only support for the idea that I've ever heard of is some parts ID article in some car magazine written decades after the cars were built, which is obviously not a reliable source!

 

I had a gentleman on ChevelleStuff.com/forums a couple of years ago with an E 5 7 dated 3917124 rear end in a 67 SS396. I'll try to contact him and see if he knows, or can get, the measurements on it.

 

Good deal. Would be great if he can give the assembly date on the axle too, since a May casting date pumpkin also could have been used in a 68 model year axle assembled in July or August, that later made its way into a 67 vehicle.

Thanks!

 

Just heard back, he's sold the car.

 

Aw man... I've got a 67 12bolt and a 68 12bolt under the cars with flat tires out in the weeds.

I sure do hope sumbody else has the answer.

 

Dale and Jeff, my Baltimore 07D '67 L79 Malibu is cast NF 3917124, E 6 7. For some reason the stamped codes are ground off except for the B POP reads KF 0620 B and it is 3.55 posi. Backing plate to backing plate is 53 1/4" and drum to drum overall is 60".

 

Dale and Jeff, my Baltimore 07D '67 L79 Malibu is cast NF 3917124, E 6 7. For some reason the stamped codes are ground off except for the B POP reads KF 0620 B and it is 3.55 posi. Backing plate to backing plate is 53 1/4" and drum to drum overall is 60".

Thanks, Bill. It appears to be the narrow version. Goes to show you can't always trust automotive magazine articles.