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Old 02-27-2002, 12:05 AM
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69dartgt 69dartgt is offline
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Default 8 1/4" Rear End Swap

I want to trade out the tired 7 1/4" rear end in my 69 Dart for an 8 1/4" from a donor Dart of approx. the same year. Can anyone tell me if I will have to modify (cut, hack, shorten, lengthen) my driveshaft, and are the u-joints the same (I believe they are). Any help would be greatly appreciated.
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Old 02-27-2002, 12:49 AM
slimegreen slimegreen is offline
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I did the same swap in a 72 duster. The u-joints are the same, but you will have to cut out 1 1/2 inchs from the drive shaft.
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Old 02-27-2002, 01:28 AM
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Ausydad Ausydad is offline
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I agree the u-joints were the same on my '74, although I had to cut more. Go to Napa before you cut out the old one and order the new U-Bolts. Once the rear end is in place, measure from the tip of the splines of the trans tailshaft to the center of the u-joint cup on the rear yoke. Take that measurement to you driveshaft guy. He'll make the cut, add a new yoke, and balance the unit. Should be less than $100. If you're going 727, now's the time for that too so you only have to cut once. Good Luck!
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Old 02-27-2002, 08:20 AM
duster360 duster360 is offline
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dont forget to get the spring plates as the 8 1/4 has 3" axle tubes and the 7 1/4 has 2 3/4 tubes also theres a possiblility of a different bolt patteren
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Old 02-27-2002, 08:29 AM
jelsr jelsr is offline
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The difference is 1.6" from axle center to yoke center on the rears. 10.09 for the 7-1/4 and 11.69
for the 8-1/4. Mopar offered 2 sizes of joints in those days, large and small, most were the smaller size. Small is the 7260, large is the 7290. If I remember correctly they are 2-3/8 and 2-5/8 between the ears respectively.
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Old 02-27-2002, 12:12 PM
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This may help
http://members.tripod.com/~Mojo_Page/chry875.htm
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Old 02-28-2002, 06:02 PM
goldduster goldduster is offline
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The 8 1/4 has the 3" axle tubes, so that requires different shock plates and u-bolts.

The 8 1/4 was not offered in a-bodies until 1973 and ONLY came on disc brake cars with the big bolt pattern. That means that you will also need different rear wheels to match the larger bolt pattern.
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Old 02-28-2002, 10:52 PM
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when I did the same in my 69 Valiant, I used a 8 1/4 out of a 74 Dart springs and all, no problem bolted right in. The driveline did need some mods if I rember right???
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