Upgrading Rear End

[DartMan48]

Im upgrading from a 7 1/4 to an 8 3/4 on my 73 Dart and Im about to put it in and was just curious on what changes I will need to make. I know bigger U bolts but what about the piece that goes under that the shocks mount to? Do I drill the holes out bigger or get different ones?

 

[duster731]

new u bolts i got mine from autozone then you need the shock mount plates you have to get the shock mounts from a 8 1/4 8 3/4 or dana 60 same for the u bolts there all the same ex the 7 1/4

 

[racerdan80]

You'll need 3in u-bolts, you can slot the holes on the shock mount pads to accept the larger u-bolts. Are leaf springs sagging? If so they need to be replaced. Install new axle and have weight on wheels, install yoke all the way, pull yoke out 1.25 inch, measure center to center of transmission yoke to pinion yoke. Have someone help you with the measuring. If the axle has a 7290 yoke, there are conversion u-joints, Precision U Joints makes them and you can get/order those at. Any auto parts store. Remember, measure twice, cut once.

 

[DartMan48]

Thanks guys, I work at Oreilly's and got the U bolts but I wasnt sure if I could get by with the original shock mounts.

 

[racerdan80]

You can get new shock pads for 100.00 from mancini racing. The slotting is minimal, only a quarter of an inch for and aft. Just remember when grinding or drilling to go slow and keep the bits cool in oil or they will be dull in seconds.

 

[DartMan48]

What about the driveshaft? The car was stock with a Slant 6 and now has a 360 with 904 trans, will the stock driveshaft work with upgraded u-joints or will I have to lengthen or cut it?

 

[JLP]

What about the driveshaft? The car was stock with a Slant 6 and now has a 360 with 904 trans, will the stock driveshaft work with upgraded u-joints or will I have to lengthen or cut it?

The driveshaft will have to be shortened and I would recommend new U-joints.