GM Stocker rear end
 

Are the 9” rear ends in the COPO’s considered a corporate replacement to the older stocker’s or are they limited to the COPO’s only? I think I know the answer, but I have to ask….
Thanks, Mike

Re: GM Stocker rear end
 

That's a really good question. The rear suspensions on the Chevrolet, Ford, and Chrysler factory racers are nowhere near stock configuration, which in my opinion these cars should be using the stock suspensions with the same approved modifications the older cars are allowed. Are the older stockers allowed to use the same technology as the factory built cars? I think not. Also, the newer designed engines have features which allow them to make more horspower and torque per cubic inch than the older engine designs. One item that comes to mind is a roller cam.

Re: GM Stocker rear end
 

The older IRS Corvettes have been allowed to install a solid axle in for years. The COPO rearend, which is based on a 9" Ford, is not legal in the other GM stockers.

Re: GM Stocker rear end
 

I'm not so sure about that...

"Original rear end may be replaced with another from the same
automobile manufacturer; truck rear end prohibited. Aluminum
center section permitted only on vehicles that were originally
equipped with same. Distance between backing plates may not
be changed. Any gear ratio that fits third-member case or
housing permitted. Limited-slip or ratchet-type rear ends
permitted. Reinforcement of spring perch permitted. Spools
permitted only with aftermarket axles. Aftermarket axles not
required for front-wheel-drive vehicles. Larger brakes may be
used. Replacement rear end may be narrowed or widened to
obtain original rear-end width. Bracing or beefing up the rearend
housing permitted.
Swing axle differential may be replaced with conventional
housing; stock trailing arms must be retained, may be beefed up
and adapted to housing, must retain transverse spring. Must
install Panhard bar. Frame may be notched for driveshaft
clearance. Distance between OEM backing plates and OEM
wheelbase must be maintained. Coil-over shock or four-link
adaptations prohibited. See General Regulations 2:11."

As I see it, GM's '(9")" is now in the mix. We already run aftermarket 12-bolts...what is the difference with this one? "Original rear end may be replaced with another from the same
automobile manufacturer" ;) Let the legal interpretation of the rules begin. :p

Re: GM Stocker rear end
 

The 9 inch rear end in the COPO cars, is built by Strange exclusively for GM and the COPO program. Not available to the public, unless you buy a COPO of course.

Re: GM Stocker rear end
 

"Original rear end may be replaced with another from the same
automobile manufacturer"

That wording is not in the rulebook. In my mind it makes no difference who made the housing...it is still from the same car manufacturer. Did the COPO cars not have to meet the minimum requirements to qualify for Stock classes? My Mosier or Strange 12-bolt housing was not built by Chevrolet, but are none the less considered legal...correct?

Re: GM Stocker rear end
 

OK, now, is the COPO rear end in the Camaro built by Ford or an aftermarket supplier? Seems to me most rear ends are made by Eaton,Spicer,Dana or some outside party like that. Does that mean I could put a rear end that is a facsimile copy of a 9 inch Ford,although not made by Ford specifically, in my 327 powered '68 Chevelle?With the currently increasingly more difficult to locate and expensive OEM 12 bolt housings becoming more and more of a problem, does that qualify me to install an aftermarket nine inch under it? I think of our buddy Aubrey Bruneau with his 4 speed 409 Chevy Bel Air bubbletop who could really benefit from that. The fact that Ford doesn't and hasn't produced those rear ends for 30 years or so,and aftermarket suppliers are now supplying them to Drag Pak and COPO racers under their factory race cars,(which are themselves outsourced),does that constitute a loophole through which they could be legalized for other applications? Just a thought on a boring cold night.

Re: GM Stocker rear end
 

A copy and paste of the rule book means absolutely nothing. Once again, the rules apply to some and not others.

A prime example would be a red Olds stocker that recently moved from the west coast to the east coast. It has been through tech many times and always passes. I believe it just won a divisional as well. But it clearly has a narrowed rear axle and altered frame rails. There is no other G body car that sits as low to the ground and has the tire clearance this car does. How is that possible??

A simple check of the distance between the backing plates and between the wheel wells may shed some light on this. But NHRA NEVER checks these things. They must not own a tape measure.

I doubt they even care about bogus stuff like that. Otherwise they wouldn't allow even half the junk they do. So I say, stick the nine inch Ford in. IF they catch it, as for forgiveness.

Re: GM Stocker rear end
 

Officially NOT I repeat NOT for use in ANYTHING except COPO cars. Was told that with EXTREME prejudice by GM officials AND NHRA tech when wanting to replace my 12 bolt. Huge debate on the floor at SEMA Went rounds explaining and arguing my case and was finally told"You want to use the new rear end? Buy a new car and get rid of your old one!"

Re: GM Stocker rear end
 

I thought you could buy all the required parts to build copo's drag pak's etc over the counter. If so then why not order your gm or mopar 9"? Then it would have to be legal having the gm or mopar part number affixed! The big wigs at sema argued this you say, but would tech?