Project "Front-End"

Mitsubishi on 4x4Wire Short Cuts

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Part 1: Upper Control Arm Bushing/ Shaft-Replacement

Project "Front-End"

This month I will begin Project Front End, by replacing the upper control arm shafts and bushings. This should go a long way towards eliminating the clunking noise which has plagued this vehicle for 6 months.

Keep in mind that if the shafts have worn too much, and the arms themselves have also deteriorated, then you will need to replace them as well.

Diagnosing the Problem

Using a pry-bar to check for play in the front-end.

To determine if your vehicle is a candidate for this repair, place a hilift jack under the front bumper, slightly raise the vehicle, and remove the front wheel. Roll a floor jack under the lower arm, and slowly raise it, to take the tension off the upper arm.  Place a pry bar between the upper arm and the frame and look for movement (I was shocked to find over 2" of play when I did this!). If the movement is in the area of the shaft which attaches the upper arm to the frame, then proceed with the repair. If there is no movement in the UCA, check for play in the pitman arm (driver's side), idler arm (passenger's side) and the balljoints.

Parts shopping

The new "shaft kit" from Moog comes with all required hardware.

When buying the parts for this project, you may consider purchasing the whole upper arm, but this is a lot more expensive, and often not necessary. When you order the parts, ask for an "Upper Control Arm Shaft Kit". This comes with the grease nipples, the shafts, the end bolts, and the inner and outer bushings. You will also need some good multi-purpose grease. You will need to re-use the bolts that attach the arm to the frame. My shaft kit came from Moog Engineering, and was part # K9399.

The Procedure

Begin this repair by jacking up the front bumper, removing the wheel, and placing a floor-jack under the lower control arm, to reduce tension on the upper arm.

Editor's Note: Note that this fix can be made problematic by seized or rusty bolts, so a heat source might be necessary to remove the hardware.  It is also recommended that a wheel alignment immediately follow this fix, since the alignment shims will be "tampered with" during the repair..

Removing the Old Shaft

newvsold.jpg (91374 bytes)
Remove the old grease nipple from the shaft.
The old shaft is worn so much that a taper is noticeable on the end.

Remove the old grease nipples on either end of the shaft with an 8mm wrench, or a pair of locking pliers.  Now the fun part: place a large wrench (1 1/8 or preferably the metric equivalent) on each shaft end nut, and remove it. If the nut is stubborn, apply some penetrating fluid, and give it a few taps with a hammer. If this does not convince it to come off, carefully apply a heat source to the nut.

After the end nuts have been removed, turn your attention to the bolts holding the shaft to the frame; these are best removed with an assistant. Have somone hold a wrench on the nuts (from under the hood) and turn the bolts, with an impact gun if possible, from inside the wheel well. At this point you have to be careful not to lose or misalign the alignment shims between the frame and the shaft, since even a minor adjustment can adversely affect your wheel alignment.

After removing the frame bolts, the shaft can be removed. This is expedited by cutting away the old bushings, but be sure to note how they go on, so the new ones will mimic their position. Also note that you may need to adjust the height of the lower control arm (via the floor jack) in order to sremove the shaft. When you remove the shaft, look for wear on the ends...mine was actually tapered off (can you say "procrastination?"). Once the old shaft has reluctantly left its home, its a good idea to check the inner threads of the UCA to make sure the arm itself is not worn too much to re-use.

Installing the New Shaft and Bushing

tn_newvsold.jpg (3105 bytes)
New versus old: Notice how much is left of the old bushings!

Slide the new bushing in place on the shaft, and squirt some grease inside (be sure to remember how the old one was oriented). Now you can snake the shaft into position on the arm, as you move the lower arm up or down to accomodate it. Carefully, so as not to disturb the alignment shims, bolt the shaft onto the frame again, and then thread the end nuts onto the arm. Tighten the frame bolts, and then tighten the end nuts, making sure that the bushings are sitting in place properly.  Finally, screw in the new grease nipples, and pump up the bushings with grease.

*Since this installation involves front-end geometry, it is advisable to get a front-wheel alignment right after performing this repair.


This project's difficulty lies on the removal of large, often stubborn nuts and bolts. If these can be  successfully removed, the rest of the repair is relatively straight-forward.  It is advisable, if possible, to remove the shaft and check the condition of the arm itself before buying parts, in case it is badly worn.

The next chapter in this project will look at replacing the front shocks; look for it in the coming months!

Contacts: Related Links:

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