Measuring driveshaft length

[Chatt69chgr]

I am converting my 318/904/8-1/4 69 Charger to a 440/A-833 4-speed/8-3/4 configuration.  The differential will be a 489 with 7290 pinion yoke.  The A-833 will be a 23 spline with 30 spline output shaft and 66-69 tail housing.  I have a lead on a drive shaft with slip yoke that supposedly has 7290 u-joints.  I will be taking my tape measure and would like to know what the correct length is that I should be looking for.  I suppose the best measurement would be from the centerlines of the yokes that are a permanent part of the driveshaft at each end.  Also, I would lay the driveshaft on the ground and measure the length from the tip of the slip yoke to the other end of the driveshaft (ie, to the rear centerline of the rear u-joint.  I know how to tell the difference between a 7260 and 7290.  Not sure I know how to tell a 1330.  Also, what is the correct diameter of the driveshaft?  Price quoted is $100.  Is this the going price?

[Chryco Psycho]

7260 u joints are 2 1/8" inside the loops that hold the cups in , the 7290 is 2 5/8 ", the driveshaft will typically be 3"
I do not have a measurement for you on lenght though , the 904 needs a 4" longer shaft than the 833 + the 8 3/4 diff will have a longer pinion on it than the 8 1/4 but I am not sure how much longer 

[Chatt69chgr]

Thanks Chryco---------this data shouldl allow me to derive the driveshaft length.  The dimension from the centerline of the axle to the centerline of the u-joint for a 8-1/4 rear end is 11.69 inches and for a 8-3/4 it is 12.35 inches.  So I need to measure my existing driveshaft and first take off 4 inches for the A-833 and then another 0.66 inches for the 8-3/4 differential.  That should yield the correct length for a 4-speed 8-3/4 rear end 69 Charger driveshaft.   

[tecmopar]

Don't know what you have installed yet so this may not help, but, if the motor, trans and rear are installed, place jack stands under the rear to get the full resting weight on it. Then measure from the end of the tailhousing ( no seal ) to the C/L of the rear yoke. Now subtract 3.5" and this is your C/L to C/L measurement for the drive shaft, good luck.

[Chatt69chgr]

I measured my driveshaft on my 318/904/8-1/4 car and found it to be 56-7/8 inches long centerline of front u-joint to centerline of rear u-joint.  I then subtracted 4 inches for the future A-833 and another 0.66 inches for the increased length of the future 8-3/4 over my 8-1/4 (I assume 741's, 742's, and 489's have same dimension between axle centerline and centerline of u-joint) and end up with a driveshaft length of 52.215 or rounding it off approximately 52-1/4 inches long centerline to centerline from the front to the rear u-joint. 

So to summarize: I believe the driveshaft length for a 1969 Dodge Charger set up with a 4-speed and 8-3/4 rear end to be 52-1/4 inches long measured between the front and rear u-joint centerlines.  Can anyone confirm this?  (My car will utilize a 440 engine)

[Chatt69chgr]

I have answered my own question on driveshafts.  There is a table that can be found on the autohobbydigest.com website that lists slip yoke drive shafts from 66-74 by increasing length and gives other info (but not u-joint size).  Never-the-less, I have determined that the lengths given are centerline to centerline front/back u-joints (which makes sense).  And have determined that my 69 charger needs a 52.07 inch long driveshaft for a 440/833/8-3/4 driveline.  A very useful chart.  I have also been told that the large steel cylindrical device on the front of the driveshaft is a vibration dampener----supposedly dampens vibrations when you have got on the gas and then let off.  Driveshaft tube diameters varied from 2.75 to 3.5 inches.  Not too many driveshafts will interchange it doesn't look like.  I found out that a local driveshaft guy will make me a completely new driveshaft if I end up needing it for $200 and this is balanced/7290 u-joints and I supply the slip yoke which I have.  Just thought I would pass along what I found out for what it's worth.