Drive Shaft Length - not a metaphor

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VADodgeDart340

VADodgeDart340

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HELP!!

Drive Shaft Length on an A-Body (and this is really not a metaphor) is confusing and interesting all at the same time. There does not seem to be a book or spec sheet on different drive shaft length's dependent upon motor (not a big factor), transmission (bigger factor) and rear end (biggest factor).

So I asked a simple question and I got a complicated answer when I was with the transmission guys. So I am asking on FABO to see if the community knowledge can come to the rescue.

I have a 1972 Dart Swinger that was originally a 340/727 car. Right now it has a 318 and a 904 automatic. It had a 7.25" rear that was translated when the car was converted from the original 340/727 to a 318/904. The drive shaft that was in the car fit but the original drive shaft is long gone (as is the original 340).

So I changed out the rear to a 8.75" but am leaving in the 318/904 while I rebuild the 340/727 (or a 360/727 - don't know yet). The current drive shaft seems to be about an inch and a half too long. The U-Joint fits fine... so that should be OK.

So here is what I need to know:

Drive Shaft length: 318/904/7.25" rear = ??"
Drive Shaft length: 318/727/7.25" rear = ??"
Drive Shaft length: 318/904/8.75" rear = ??"
Drive Shaft length: 318 or 340 or 360/727/8.75" rear = ??"
Drive Shaft length: 318 or 340 or 360/904/8.75" rear = ??"
Drive Shaft length: 340 360/727/8.75" rear = ??"

I have looked for books or guides, but the best I can find is "measure the drive shaft and then the car..." comments.

Does anybody have a guide?

Thanks in advance :bom:
 
Which s/b doesnt change the equation. 8.75 is roughly 2.25 inches bigger c/l to center of yoke than the 7.25. Why cant you slip the trans yoke in all the way and measure center of trans yoke to center of rear joint (bolt flats on yoke) with weight of car on tires? Not jacked up.Suspension has to be loaded. Then subtract 1 inch so trans yoke doesnt bottom.This will give you a correct tube length. I did this and it worked perfect. If people throw all covering numbers out there some poor guy with extended hangers is gonna end up with too short of a tube.
 
I know my dads 440/727/8.75" The Drive Shaft Length from u joint to u joint is 46-46 1/2"..I dont think it matter if its a small block or big block.. Its what kind of transmission and rear end you have.. If you have a 904 and 8.75" the drive shaft is gonna be a little longer..
 
67 Barracuda 904/8.75 = 49.25 CL to CL of U joints. I Just asked this to a guy who had one removed and a tape handy. Use this as a baseline to determine what a 7.25 rear would take (add 2.25 inches) or a 727 (subtract 4 inches)

Torqueflite%20Dimensions.JPG
 
VADodgeDart340 said:
HELP!! Drive Shaft Length on an A-Body (and this is really not a metaphor) is confusing and interesting all at the same time. Does anybody have a guide?
Click to expand...

fredsmedina said:
I'm dealing with the same thing. trying to figure out what length I need for my 318/727/8.75"rear in my '67 dart.
Click to expand...

Alright guys here the secret deal...don't tell anyone. Go to any reputable driveshaft builders web site and they will have directions on how to measure. Seriously guys this is the best way to get this done, don't try to second guess this. The link below is the company I used:
http://www.actionmachineinc.com/onepiecedriveshaftguide.aspx
 
Thanks. I did exactly that and the drive shaft went to "Drive Line" in Springfield VA yesterday

Thanks for all the help... you guys rock
 
Demon 408 said:
Alright guys here the secret deal...don't tell anyone. Go to any reputable driveshaft builders web site and they will have directions on how to measure. Seriously guys this is the best way to get this done, don't try to second guess this. The link below is the company I used:
Click to expand...


This!!!!!
 
pishta said:
67 Barracuda 904/8.75 = 49.25 CL to CL of U joints. I Just asked this to a guy who had one removed and a tape handy. Use this as a baseline to determine what a 7.25 rear would take (add 2.25 inches) or a 727 (subtract 4 inches)

Torqueflite%20Dimensions.JPG
Click to expand...

What is CL to CL of U joints? Center of U joints?
 
If the car is in your possession what do you need a book for, crawl under it & measure it.
 
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