Factory 68-71 340 727 specs

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Johnschummer

Johnschummer

FABO Gold Member
FABO Gold Member
Joined
Jan 17, 2022
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Location
Feasterville, PA
Picked up a 72 cuda H code car minus engine/trans for what I thought was a steal. I happen to have 72 340 laying in garage so off to the machine shop that went. In the mean time I picked up a 727 for 200 bucks from 73 charger which checked out serial number to be for 360/318 heavy duty and tried my hand in my first auto rebuild which has always terrified me but with help of Tom Hand’s book I feel it went well. Long story short, kept rebuild stock for the most part to keep my novice *** out of trouble which turn out the specs of that trans seem to be very similar to 72 340 auto which I understand were the lamer years 3 clutches in front drum, 9 spring. This got me a wondering and from what I read in Tom’s book 69 340 trans would have 4 clutches and 6 springs. What other parts would be different in a 68-71 340 trans? Band lever? Valve body? Governor weight thing? And how does less springs affect the trans? Few pics of car

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I had my 1971 727 apart to rebuild recently. It had 9 springs, a 3 clutch drum, 3.2 apply lever, the less desirable belville washer and a 4 pinion front planetary.

I bought a scrapper 618 from a 1997 Cummins truck and used 12 springs, the 4 clutch drum, 3.8 apply lever, deep pan, and the more desirable belville washer. The front planet was a 5 pinion metal, but had the wring spline count for my 727 so I couldn't use that. I added a transgo TF-1 while I was at it. I ditched the wave snap ring and dialed in the flat snap rings with the guidance of a couple of notable FABO Members.

Thanks @SMCARNUT and @Duster346

Hope to have the Demon up and running next season.

BTW SMCARNUT has a work around to get 4 standard clutches in a 3 clutch drum by modifying the pressure plate. Here's what he sent me.

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I have machined a few pressure plates to increase clutch plates. My swinger has 5 front clutches and 4 rear.
I also installed 4 pinion planets front and rear. If I recall, a 340 trans will have 4 pinion front and 3 pinion rear and same for the clutch packs.
Dont sweat rebuilding a mopar trans. They are the easiest of all the transmissions of the big three.
 
The less springs in the high gear drum will apply the high gear clutch quicker when the car is shifted into 3rd gear. The more power the car has, combined with the higher line pressure manual valve bodies or shift kits, the more springs you will want in the high gear drum with more clutches. If you run thin steels and clutches, you should be able to get 4 clutches in the high gear drum without issue. If you don't have anywhere to machine the pressure plate like CFD244 posted above, you can purchase a new pressure plate that is thinner to run the extra clutch, or extra 2 clutches.

Agree with MoparMike1974. Don't sweat it. These are easy to do. If you followed the book, your transmission will work fine.
 
That car looks good. How does the firewall look? I had to patch mine in my 70 'Cuda. They rust is weird places.
 
Thanks my 69 will always be my first love but the e bodys are slick. Fire wall isn’t bad, lot of surface rust. Back half car is rough. Decklid, quarters, gutters, trunk floor all need replacing and usual floors need attention.
 
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