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  #1  
Old 03-19-2009, 02:07 PM
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Blown340cuda Blown340cuda is offline
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Confused Building a 727 for a 1970 426 hemi Challenger

Hi Guy's

I'm now in the process of building myself a 727 for my 1970 426 hemi challenger , the hemi will be done up a little bit and should be in the 500 to 600 hp range and I rencently stripped a 727 that i removed from a 1972 charger s/e 400 4 barrel . I'm now in the process of replacing and changing components to accomodate my hemi. The kickdown lever in a hemi 727 i'm told is a 5.0 to 1 ratio is this true? also can i use the rest of the components in this tranny for my hemi or is there any other parts i should change? i was told the drum in a hemi had 5 clutch and this tranny only as 4 , should this be changed. Had a few telling me i should change the drum to an aluminum unit(i don't see why i should do this if it's only going to push 600hp max) am i right?. I'm looking at installing a trans go shift kit also (full manual) and a bolt in overruning clutch. Would appreciate any info.

Cheers,

Charlie B.

Mopar or no car!
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Old 03-19-2009, 04:36 PM
John Kunkel John Kunkel is offline
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The original Hemi 727 did have a 5.0 lever and a 5-disc front drum but that's seventies tech, current thinking favors a 3.8 or 4.2 lever and a 4-disc clutch.

Do you really want a full manual Transgo TF-3 kit? If so, you'd be better off with an aftermarket full manual valve body.

It would take a full page to outline all of the available 727 mods, the bolt-in sprag is on the top of everybody's list but you need to be aware that it won't prevent the most common type of failure; if you insist on using a bolt-in the Ultimate Sprag is the best one going.

An aluminum front drum isn't a good idea for the street, if you want to go billet go with a steel billet drum.
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Old 03-19-2009, 05:35 PM
Cudafever Cudafever is offline
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OK got my attention, what is the most common failure thats not related to the sprag?????


You make it sound like this bolt in sprag is just a lot of BS??????is it ???
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Old 03-19-2009, 09:40 PM
Paul Precht Paul Precht is offline
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Either sprag will break if you do the wrong thing to it. 3.8 to 4.2 is definitely the way to go. The first thing to go in my race car is always the kickdown band, but I get about 3-4 years out of them. I've broken one sprag in almost 40 years of racing and it was because I broke an axle, Paul.
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Old 03-20-2009, 03:58 PM
John Kunkel John Kunkel is offline
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The bolt-in sprag only prevents the outer cam ring from spinning in the case, this type of failure is rare. The most common failure is of the rollers and springs, this type of failure is called a "rollover" failure.

The pic below shows a rollover failure of a bolt-in sprag, the ends of the bolts are visible in the outer can ring.
Attached Images
File Type: jpg Sprag.jpg (48.4 KB, 13 views)
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Old 03-21-2009, 07:36 AM
cudabob496 cudabob496 is offline
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When I built my 496 Cuda, I spoke with the performance transmission guys to see what components they felt I should change. Think I changed out 3 diff components from a stock 727. Had them mailed to my guy who did the transmission build. Sorry I can't remember the parts, but my transmission guy said they were good stuff to ensure strength and reliability! I have a book on how to build performance 727s.
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Old 03-21-2009, 02:18 PM
John Kunkel John Kunkel is offline
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About the best book on the 727 is Carl Munroe's A-727 Handbook, it's available from Amazon.com

http://www.amazon.com/Torqueflite-Tr...7659443&sr=1-1
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Old 03-21-2009, 07:51 PM
BELVEDERE2 BELVEDERE2 is offline
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I had my 727 built by A&A Trans. Good people.
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