Chrysler Grand National Diffs

[Ghoste]

Were some of the Chrysler guys running Ford 9 inchers?  Would that even be legal?

[odcics2]

Never heard of that. 

Wouldn't be legal, either...   

[Ghoste]

Thank you.  A guy was telling me they all did and I knew that wasn't true but I did have to wonder if some used it even though it seemed to me like it couldn't be legal.

[Mike DC]

  

A guy was telling me they all did and I knew that wasn't true but I did have to wonder if some used it even though it seemed to me like it couldn't be legal.

A lot of GM (and some Ford) guys see an 8.75" axle and make this mistake.  Any banjo-style axle underneath a NASCAR gets identified as a Ford 9".  

[moparchris]

Into the 70's Petty was still using 8 3/4 diff's.  The cars now use aftermarket versions of the Ford 9".

[Aero426]

Even when Nichels ran the Pontiac and Chevelles in '71 and '72, they used the Chrysler rear end.

[Ghoste]

That surprises me a bit because I thought they would have to run a corporate branded "stock" rearend.  I realize now they all run aftermarket Fords but I would have thought factory up until the 1980-ish.

[Aero426]

That surprises me a bit because I thought they would have to run a corporate branded "stock" rearend.  I realize now they all run aftermarket Fords but I would have thought factory up until the 1980-ish.

I don't think GM had a diff setup that allowed you to easily to change gear ratios like the Chrysler or Ford design.   They also had to run the 2 door GM cars on the 4 door wheelbase to comply.   It looks odd when you spot it. 

[wingcar builder]

Smokey run a 9" in the Chevelle. GM didn't have a rear that was fast to change gears.

[Ghoste]

So it would have been perfectly legal for any Chrysler team to run the Ford rear back in the Golden Age?

[Mike DC]

 
Axle swapping in NASCAR goes beyond the drop-out diff issue.  They started swapping axles & running full floater hubs in the mid-50s for safety reasons.   

Hudson Hornets were the car to have for a couple years there.  But when they broke an axle shaft the low rear fender skirts entrapped the loose wheel, and it would get tangled up with the leaf springs & housing.  A lot of Hornets got violently rolled over.  Dirt tracks + stock axles + welded spider gears = very common problem.

[warmpancakes]

I know Cotton owens has some oddball diff housings in his shed they were sent direct to him from Chrysler,  hopefully rarebird will pop in he talked with him about them

[Aero426]

So it would have been perfectly legal for any Chrysler team to run the Ford rear back in the Golden Age?

Per the rule book, it appears you could do this if so inclined.    Differentials appear to be an open book, but no quick change allowed, and must maintain track width.

[Ghoste]

Do you know of any Chrysler guys running a Ford rear back in the day then?

[Aero426]

Do you know of any Chrysler guys running a Ford rear back in the day then?

No good reason even for an independent to do so, that I know of.   The Chrysler unit was strong enough and readily available.

I have to assume the Matadors ran a 9" as they were built at shops previously affiliated with the Ford side of things.  

[Ghoste]

Cool thanks.  I just want to be fairly sure the next time I see this guy and challenge him to bring me proof.

[Mike DC]

                                                                       
If you don't need a 9" then there is an incentive to avoid it.  The 9" has more parasitic drag than the Mopar rearend. 

It's because of the pinion location & gear mesh pattern.  It gives the 9" huge strength potential without a giant-size ring but it also makes the diff run hot and cost horsepower.