Overview
The Pro Comp 58401 is a 4 inch rear lift block kit for leaf spring vehicles. The kit includes two tapered cast iron riser blocks, four U-bolts, eight heavy duty flat washers and eight hi-nuts.
Tapered riser blocks are shaped to improve driveshaft angles at the raised rear. Confirm fit for your vehicle’s year, model and trim before ordering.
Key features
- 4 inch rear lift
- Tapered cast iron riser blocks
- Four U-bolts for mounting to the springs
- Heavy duty flat washers and hi-nuts included
Tapered blocks and driveline angles
Tapered blocks are thicker at one edge, so the axle sits at a different angle than it would on a flat block of the same height. That angle helps the driveshaft stay closer to its original alignment on a raised rear. Cast iron is heavy and holds its shape under load, which suits a block that carries axle weight over rough ground.
Tapered blocks only help when they are oriented correctly. Check which side is thick before installing, and confirm the U-bolts seat square on the spring pad. Once mounted, measure driveshaft angles at both ends and compare them with the original readings. If one joint sits well outside its normal range, a driveshaft with a different slip yoke may be needed.
Inspect cast iron blocks for cracks around the bolt holes after the first season of use, especially with frequent off-road work. Re-torque the U-bolt nuts after the first drives, since the springs settle slightly under load.
- Confirm which side of each block is thick before mounting
- Measure driveshaft angles before and after lifting
- Inspect cast iron blocks for cracks near the bolt holes
- Re-torque U-bolt nuts after the first drives
Specifications
| Brand | Pro Comp Suspension |
|---|---|
| Part number | 58401 |
| UPC | 614901111309 |
| Type | Rear block with U-bolt kit |
| Lift height | 4 in |
| Block material | Cast iron |
| Block shape | Tapered |
| Hardware | 4 U-bolts, 8 heavy duty flat washers, 8 hi-nuts |
Vehicle fitment
Check the rear axle and spring pack against your vehicle before ordering this kit.
Confirm your vehicle’s year, model and trim before ordering.
Installation notes
A 4 inch lift changes the spring and driveline geometry, so check driveline angles and U-bolt clearance after installation.
What’s included
Two cast iron riser blocks, four U-bolts, eight heavy duty flat washers and eight hi-nuts.
