Overview
The TeraFlex 3440020 is an upper and lower ball joint kit with knurling, made for Dana 30 and Dana 44 front axles on the Jeep Wrangler JK. The knurl suits knuckles with a loose press fit, which can develop after repeated ball joint replacements. It fits 2007–2015 Wrangler JK models.
The kit is designed for the extra load from oversized tires and offset wheels. The upper joint has hard sintered bushings, and the lower joint has a threaded top cap for preload and a grease passage for service without removing the axle shaft. It is a direct replacement for 2007–2011 and most 2012 models. The knurl is intended for knuckles with a loose press fit, and non-knurled joints will not score the inner knuckle or open up the bore. The lower boot is locked in place with a spring and a spring steel ring, and the adjustable end cap gives lateral greasing access.
Key features
- Knurled ball joints for loose knuckle bores
- Sintered bushing in the upper joint
- Adjustable preload on the lower joint
- Greasing access without axle shaft removal
- Magnesium phosphate coated 4140 chrome moly ball and stud
Knurled fit and alignment
A knurled joint relies on its outer ridges to bite into the knuckle bore, so it is a fit choice rather than a general upgrade. Before pressing one in, measure the bore and look for scoring or ovaling, which are common reasons a joint spins in place. The knurl should match the bore condition, since using it in a sound bore can damage the knuckle.
After replacement, recheck steering play, torque the castle nut to the value given in the service procedure, and confirm the retainer is secure. Greasing the joint through its passage keeps the bushings and seals working. A front alignment check is a practical step after any ball joint job, because small changes in joint height can shift camber and toe.
- Measure the knuckle bore before choosing knurled or non-knurled
- Confirm the castle nut is torqued and secured
- Grease the joint after the first few drives
Specifications
| Brand | TeraFlex |
|---|---|
| Part number | 3440020 |
| UPC | 843885031871 |
| Joint type | Upper and lower kit |
| Knurl | With knurl |
| Upper bushing | Sintered |
| Ball and stud | 4140 chrome moly, magnesium phosphate coated |
| Housing | 1045 carbon steel |
| Lubrication | Grease fitting, lubeable |
Vehicle fitment
It fits 2007–2015 Jeep Wrangler (JK) models, including Rubicon, Sahara and Unlimited versions. As a direct replacement it suits 2007–2011 and most 2012 models. Compare your vehicle’s year, model and trim with the fitment before ordering.
The TJ, LJ and JL Wrangler are outside the listed years. Confirm your vehicle’s year, model and trim before ordering.
Installation notes
Late 2012 and newer JK models require modification before this kit fits. Some 2012 and all 2013-and-newer JK front shafts are larger, and they need grinding on the stub shaft forging parting line for clearance.
What’s included
One upper and one lower ball joint with knurl, including the castle nut and boot.
