i didnt do anything to the driveshafts or sye. it had no vibes. i would recomend the spacers with 33s especially if your haveing a winch and accessories.
2004- Wrangler X stock
1977 full size cherokee-401 v8, quadratrac dana 44s
prev. jeeps: 98TJ on 33s, 00TJ on 35s, 01TJ on 35s, 78CJ on 31s, 85XJ stock, 94ZJ stock, 97 TJ on 35s, 03 on 35s, 93 GC on 33s