Synergy Heavy Duty Ball Joints Front 1 Upper/1 Lower 4140-6004 for 1984-2006 Jeep XJ/MJ/YJ/TJ/LJ and 1993-1998 ZJ

Our Synergy Jeep TJ / LJ / ZJ / XJ / MJ / YJ Heavy Duty Ball Joint Kits replace your Jeep’s factory ball joints with heavy duty ball joints. After over 5 years of development and over 500,000 test miles of research and development and serious abuse, these ball joints are the highest quality ball joints on the market. Our fully greaseable metal on metal design improves durability and performance. The extra large ball joint bearing surface eliminates the inner nylon liner, creating a longer lasting, more reliable joint. If you have a lifted jeep, then you need heavy duty ball joints to put up to the abuse of bigger tires and offroad riding.
Fitment:
Part # Description Fitment
4120-04 (1) Knurled Upper Ball Joint
(1) Knurled Lower Ball Joint 1990-1992 Jeep Comanche MJ
1990-2001 Jeep Cherokee XJ
1987-2006 Jeep Wrangler YJ / TJ / LJ
1993-1998 Jeep Grand Cherokee ZJ
4120 (2) Knurled Upper Ball Joints
(2) Knurled Lower Ball Joints 1990-1992 Jeep Comanche MJ
1990-2001 Jeep Cherokee XJ
1987-2006 Jeep Wrangler YJ / TJ / LJ
1993-1998 Jeep Grand Cherokee ZJ
4140-6004 (1) Non-Knurled Upper Ball Joint
(1) Non-Knurled Lower Ball joint 1990-1992 Jeep Comanche MJ
1990-2001 Jeep Cherokee XJ
1990-2006 Jeep Wrangler YJ / TJ / LJ
1993-1998 Jeep Grand Cherokee ZJ
4140-60 (2) Non-Knurled Upper Ball Joints
(2) Non-Knurled Lower Ball Joints 1990-1992 Jeep Comanche MJ
1990-2001 Jeep Cherokee XJ
1990-2006 Jeep Wrangler YJ / TJ / LJ
1993-1998 Jeep Grand Cherokee ZJ
See our Synergy HD Ball Joints for 1999 – 2004 Jeep Grand Cherokee WJ and 2007 – 2017 Jeep Wrangler JK / JKU models here!
Benefits:
Compatible with all aftermarket axle shafts (including RCV’s) with no modifications needed
Without the inner nylon liner, the ball joint bearing is significantly larger than stock leading to a longer lasting joint
Maximum strength and reliability due to the heavy duty steel design on all hard components
Heavy duty dust boots are made out of industrial grade, wear and tear resistant black nitro-butyl rubber (NBR) to prevent premature rips or tears
Available in both knurled and non-knurled options
Fully greaseable, metal on metal design provides smooth operation and
Features:
Sintered graphite & oil impregnated bronze ball joint bearing race for a strong, smooth, bearing surface
1045 high carbon alloy steel ball joint housing
Ball joint stud is induction heat treated 4140 chromoly steel for maximum strength and reliability
Industrial grade, wear and tear resistant black nitro-butyl rubber (NBR) dust boots
Includes:
4120-04 4120 4140-6004 4140-60
(1) Knurled Upper Ball Joint
(1) Knurled Lower Ball Joint
(2) Castle Nuts
(2) Cotter Pins
(2) 1/4″-20 UNF Grease Zerks (2) Knurled Upper Ball Joints
(2) Knurled Lower Ball Joints
(4) Castle Nuts
(4) Cotter Pins
(4) 1/4″-20 UNF Grease Zerks (1) Non-Knurled Upper Ball Joint
(1) Non-Knurled Lower Ball Joint
(2) Castle Nuts
(2) Cotter Pins
(2) 1/4″-20 UNF Grease Zerks (2) Non-Knurled Upper Ball Joints
(2) Non-Knurled Lower Ball Joints
(4) Castle Nuts
(4) Cotter Pins
(4) 1/4″-20 UNF Grease Zerks

Notes:
Synergy High Performance Grease recommended
Metal on metal ball joints require a small break-in period of typically 100-500 miles to fully “seat” the bearing surfaces. During this time the steering may feel “sticky” or slow to “return to center”. Once broken in, the steering will be smooth and tight
Knurled ball joints are required when replacing ball joints that have enlarged ball joint bores; It is up to the installer to verify proper fitment
View our 12 Month Unlimited-Warranty
More information: www.p65warnings.ca.gov