proper length of driveshaft

[hartigan1]

I have a 72 challenger. Originally 318. It will have 400 block and 727 with 8.75 rear.
Question: What is the proper driveshaft length and how do I measure it. I found one at a boneyard but don't know if it is correct.
Thanks,
H

[Chryco Psycho]

any Challenger with a 727 trans & 8 3/4 diff will be the same length but you still have to watch the U joint size

[CrazyPete]

when i did my bb swap years ago on my Gran coupe it was a 318/904 car i had to shorten my driveshaft about 3 1/2 " for the 440/727 good luck

[hartigan1]

Are there any measurements I can make to determine if the driveshaft is the correct length. I want to get one used but I need to know this info. I am trying to get one from a salvage yard and the parts are no longer mated to cars. I don't have a spare to use as a model or guide to picking out another.

[70challengerrt]

I am looking in the challenger-cuda restoration guide from paul herd and the closest I can find is:
1971 challenger
Type      engine     Trans     Axle    ratio    length    dia
7290      318          man      8 3/4  3.23     45.60     3 1/4
7290      383          all        8 3/4   3.23     45.85     3 1/4
7290      340,383    all        8 3/4   all        45.60     3 1/4
7290      440          auto     8 3/4   all        43.60     3 1/4
7290      440          all        9 3/4   all         42.60    3 1/4

the way it looks 45.60 would be the way to go better to have the little extra play. It you slid a tranny yoke in then pull back 3/4 to 1 inch and measure center or u joint to center of u joint is the best way because you know the shaft is right.

[matt63]

I just slide in a spare transmission yoke all the way and measure the center to center distance and subtract 1/2 to 3/4" to obtain the required driveshaft length.  If you find a longer driveshaft with correct yokes it can be easily shortened and rebalanced.  New u-joints are always a good idea too.