7260/7290 factory application

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Vitamin c

Vitamin c

Vitamin c
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My 69 swinger 340 automatic came with a 7290 joint drive shaft. My 70 swinger 340 4-speed came with a 7260 joint drive shaft. What determined which size joint was installed from the factory? Im getting the drivetrain ready for the 70 swinger and just find it strange that it has a 7260 joints. anyone have any information on this?
 
Actually it's strange to see 7290 joints in a A-body unless it was a big block car. All small block A-bodies I've seen had 7260 U-joints. Do you suppose someone could have changed the one in your 69 to the larger 7290's?

Just a tidbit more info: concerning the strength of the 2, I've seen cars running 10's with 7260 U-joints. Solid joints of course are stronger.
 
yeah...71 Dart has 7260 front and rear u joints..

71 Demon has front 7260 and rear combo 7260/7290 u joint
 
It appears both cars have the original shafts. When I picked up the 70 I was wanting to turn it into a strip car, so I sold the original 8 3/4(don't recall the casting #) for a 489/7290 8 3/4 with 4.10 gears. I was set on having a new shaft built, so I didn't concern myself with the small joints. Now that the car has taken on more of a stock build I was wanting the original style drive shaft. I could probably use the combo rear joint and be done with it, but just wanted to throw this out there for some opinions.
 
I just switched my 68 dart to the large u joint and at the same time a fresh rebuilt 489 center section. The rear end yoke for the large u joint was $140.
 
Factory only used 7290 in trucks and hemi/6pk stick stuff and some odd c body stuff, and some trucks, and fewer trucks had the 5380, even most 1 tons had the 7260 joint
 
Vitamin c said:
Hmmmm, now im really baffled.
Click to expand...


I have seen little reg cab, short bed W250 /6 3 spd p/u with 5380 series and CC W350's V8 4 spds with 7260 series.
When you think about the power and gearing between the 2 wth did they put a 5380 in a lil /6 with no torque ability with the gearing or the ability to work the joints, and the truck doesn't have the rating to do as much ?
Then in a 1 ton with a 8 a killer 1st gear and it has the ability thru gearing to make enough tq to exceed the rating of the 7290 and they put a 7260 in it and the lesser truck has a 5380. . . . . insane
 
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