COPO 12 Bolt Posi Carrier....
 

How do I know for sure that I have one? I have tried using the search function on this website... but haven't found any hardcore evidence. Seems like the guys who know these things want to keep them under wraps.
-Matt

Re: COPO 12 Bolt Posi Carrier....
 

Forgot to mention that the unit in question is a small window 174 carrier.

Re: COPO 12 Bolt Posi Carrier....
 

Ping Eric he is the king of posi's, 69L72RS

Re: COPO 12 Bolt Posi Carrier....
 

Post a pic of it here - with Eric's help he will be able to indentify from just a few photos.

Re: COPO 12 Bolt Posi Carrier....
 

Hi Matt,
Post a picture or email me one of the internal parts thru the large case window.
I should be able to tell from that.
Eric

Re: COPO 12 Bolt Posi Carrier....
 

Here we go guys. Just got time to snap a few photos and post them here. What do you think?

http://i373.photobucket.com/albums/o...o/IMG_8091.jpg
http://i373.photobucket.com/albums/o...o/IMG_8092.jpg
http://i373.photobucket.com/albums/o...o/IMG_8093.jpg
http://i373.photobucket.com/albums/o...o/IMG_8094.jpg

Re: COPO 12 Bolt Posi Carrier....
 

That is a standard 4-series posi unit.
The spring plate have the obround holes for the c-clips.
The axle gears look like they are the 17 tooth gears, because they have flat tips and the teeth roots are too high above the clutch packs.
The B-7-J would be the assembly date of February 7th 1969.
That would be a good unit for a late February or March assembled BV or KK rear end.
Hope this helps.
Eric

Re: COPO 12 Bolt Posi Carrier....
 

Ahhh... One of these days I hope to snag one! Thanks for the ID Eric!
-Matt

Re: COPO 12 Bolt Posi Carrier....
 

Glad to help.

Re: COPO 12 Bolt Posi Carrier....
 

The copo posi unit uses standard non posi sized spider gears. They are smaller than traditional posi spiders so they can match up with the larger copo axle gears. Hard to explain with only one cup of coffee.

Re: COPO 12 Bolt Posi Carrier....
 

MacNeish wrote a whole chapter on this 234 COPO unit in his Camaro book. Lots of photos. Me and my boys have been to his shop and he's been doing rears for over 40 years!

bob

Re: COPO 12 Bolt Posi Carrier....
 

Here are the part numbers from the COPO differentials.

Also Charley is close(must need more coffe). https://www.yenko.net/ubbthreads/imag...mlins/haha.gif
The carrier case is the standard 30174 case that has different internal machined dimmentions to allow the larger axle and pinion gears to fit properly.

3916234 Differential, w/case (special diameter)
3918831 Gear, Differential (special diameter)
3918832 Pinion, Differential; ECN May of 69
3918833 Washer, Differential Pinion Thrust; ECN May of 69
3881140 Pinion, Differential
3881141 Washer, Differential Pinion Thrust
3918834 Plate, Differential Clutch Pressure
3957939 Spring 75lb. each (natural color)

3917971 Gear Assy, 4.10 ring and pinion, speacial heat treat
3917973 Gear Assy, 4.56 ring and pinion, speacial heat treat
3917972 Gear Assy, 4.88 ring and pinion, speacial heat treat

Notes:
3918832 Pinion, : 9310 alloy to match axle gear
3918833 Washer, : has no indexing shoulder
3881140 Pinion, : 8620 alloy
3881141 Washer, : has indexing shoulder (pain the ass to assemble with these)

Hope this helps.

If one of the MODS will make a sticky, I can provide a detailed photo set of these parts COPO vs standard.

Re: COPO 12 Bolt Posi Carrier....
 

I saw many of the 234 pieces at CHP while I was there. He has quite a selection of pieces parts from when he marketed this carrier for drag racing back in the early 1970's. Also saw one of the 877 trans am carriers there.

Bob