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73 roadrunner big block driveshaft length

adk-roadrunner

adk-roadrunner

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I know there have been a ton of threads on driveshaft length but I cannot for the life of me find the proper length of a driveshaft for a 73 roadrunner with a 440, 727 and an 8 3/4 rear end. I'm getting ready to swap my new 440 into my 73 roadrunner with a 318 and I need to know what length shaft I need. I have no place closer than 3.5 hours away that can shorten my driveshaft but even if I did I still need to know how long it needs to be. I would really like to have the shaft ready so I can make the swap in a few days with minimal down time. If there is anybody out there that is willing to measure the shaft on their 73 roadrunner with a big block ,727 and 8 3/4 rear end it would be great as I am extremely sick of searching non stop for the proper length. I believe you are supposed to measure from center to center of the u joint caps. thank you for your time
 
I have a 74 charger that was a 318 car and I put a stroked 400 with a 727 in it and a 8 3/4 rear. I used the original setup driveshaft and had no issues. . . Sounds strange but worked on my car
 
I guess I should have stated that I going from 318,904 and 8 1/4. Did your charger have the 904 or 727 I think that's the difference.
 
You really need your slip yoke to get a proper measurement...bottom it out in the trans then pull it out 3/4" (some go 1 inch) Then measure from center to center of u-joint cups with the weight of the car on the tires (suspension loaded normally)
 
I find it so hard to believe that nobody knows the length of the factory driveshaft for this combo. Mopar's can be such a pain I really need to find out the length before doing the swap otherwise the car will be sitting for 2 weeks waiting on a driveshaft. Gotta keep searching
 
Measuring it yourself is the only way to be truly accurate and most any shop or supplier will say the same. Your FSM will also list the different factory length shafts offered that year. If you don't have one you can download them online
 
The way I always did it was-

On a lift, put the slip yoke in the tail shaft and pull it out about an inch (because the axle is dropped), then hold up the rear and measure how far too long it is between the center of the U joint caps and the center of the yoke clamps.

Not perfect but works.

You could also put something under the rear wheels to hold them close to the correct height.
 
Than you for you time and answer the problem is the new engine, transmission and rear end are not in the car yet. The reason I was asking for some one to measure their stock driveshaft with same combo was because I will only have lift for so long. I wont be able to wait for driveshaft shortening or waiting for a new shaft to be ordered and come in. I'm just trying to be as prepared as possible for the complete swap so it goes as smooth and quick as possible. Than you everyone for all your input and help.
 
You can install it while the car is on the ground.

You can measure for it that way too, but it's MUCH easier to do the measuring while it's in the air.
 
Please, no offense meant, but they are trying to tell you to put your foot in the shoe before you tie it.
I understand what you are trying to do though and there is another way that may work. Find out how much shorter a 904 is than a 727, then find out how much longer an 8 3/4 is than a 8 1/4 (from axle centerline to yoke face), add together to find out how much to shorten your shaft. That info may be available from tech archives or from driveline forum.
I wouldn't do it that way.
Also the likelyhood of a swap that involved being done quickly is pretty darn small.
 
I had a custom driveshaft made for my 74 roadrunner, with a 440, 727, and 8 3/4. The measurements I have on hand are from the centre of the pinion end u joint, to the face of the transmission output shaft- 53" 15/16. Transmision housing to end of output shaft- 1" 3/16.
 
adk-roadrunner said:
I know there have been a ton of threads on driveshaft length but I cannot for the life of me find the proper length of a driveshaft for a 73 roadrunner with a 440, 727 and an 8 3/4 rear end. I'm getting ready to swap my new 440 into my 73 roadrunner with a 318 and I need to know what length shaft I need. I have no place closer than 3.5 hours away that can shorten my driveshaft but even if I did I still need to know how long it needs to be. I would really like to have the shaft ready so I can make the swap in a few days with minimal down time. If there is anybody out there that is willing to measure the shaft on their 73 roadrunner with a big block ,727 and 8 3/4 rear end it would be great as I am extremely sick of searching non stop for the proper length. I believe you are supposed to measure from center to center of the u joint caps. thank you for your time
Click to expand...
Hi I have one out of my 73 roadrunner with a big block just the drive shaft.
 
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