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Tech Question
Doug Tracy, Kidder, MO, 1980 Dodge F-M-J body 318
Rick, I need you to end a argument that I'm having with some members on Moparstyle.com. The argument is about the 7-1/4" and 8-1/4" axle. Many F-M-J body owners, who are members on that website, are are led to believe that most of their cars are equiped with 7-1/4" axles. One member even flat out told me that no Diplomat was ever equiped with a 8-1/4" axle. Several members say the only way to tell which axle you have is by the axle tubes and not the diff cover. They say the later 7-1/4" axles have 3" tubes and taper down at the diff to 2.5". They claim it has 10 bolts on the cover unlike the earlier 9 bolt 7-1/4" axles that I'm familier with. I know that 7-1/4" axles have 9 bolts on the diff cover and is irregular shaped, while the 8-1/4" has 10 bolts and the cover is oval shaped.
I've referred back to the Oct 1989 article "Bringing up the rear" (yeah, I keep all my old Mopar mags). Your article seems to agree with me. Could you shed some light on this so called 7-1/4" axle that these F-M-J bodies supposedly had?
Doug, both axles were used in F, J, and M's, from the beginning in 1976 right through the end in '89. That's a fact you can take to the bank, I have both factory documentation and personal, firsthand knowledge of these facts. The surest I.D., at least the one I've always used, is the cover shape, "regular, oval" (8.25") vs. "irregular, angular" on the 7.25". Over the years there were several design changes that make the other factors less positive -- remember, the 7.25" was released in 1960, and the 8.25, as I recall, in 1969. These are no spring chickens!
If I had to take a guess -- and this is ONLY a guess -- I'd say that, over the 13 years of production, something like 75% of these cars had the 7.25". Virtually 100% of the 360 cars, and nearly all 318 cop cars, had the 8.25", while it seems like close to 100% of the 225 cars had the 7.25. Civillian 318s were the crapshoot, the factory had a matrix of applications that depended on axle ratio, Sure Grip Y/N, wagon, tow package Y/N, etc.
So there's the light you asked me to turn on. Looks like everybody's right, and everybody's wrong -- but at least the argument is over. As a recent humorous graphic that was sent to me pointed out, (present company excepted, of course) -- arguing on the internet is like running the Special Olympics -- even if you win, you're still retarded.
Rick
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