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Pelican Technical Article:

Replacing the Steering Gearbox

Mike Holloway

Tools:

10mm, 12mm, 13mm, 17mm, 22mm socket wrenches, 12mm open end wrench, separator tool, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Mercedes-Benz R107 (1975-86)

Parts Required:

Steering gearbox Pelican part #107-460-19-01-88-M278 (C&M Hydraulics)

Hot Tip:

Make sure you collect the power steering fluid

Performance Gain:

Better handing, less vibration, smoother ride, and increased tire life

Complementary Modification:

Replace shock absorbers

If your steering is feeling sloppy and you have diagnosed all the steering components and bushings, then you may have to replace the steering gearbox. It's a time consuming job. This should only be done after all steering and suspension components and bushings have not failed. Refer to the steering component diagnosis article for details on how to figure out what may be wrong with your steering. Please note that an inch of movement in the steering wheel is ok and normal, so please do not over tighten the steering gearbox. Doing so will seriously harm it. Before you work on the steering gearbox, drain the power steering fluid from the system. Please refer to the article on draining the fluid.

After the wheels have been set to a straight-ahead position, jack up the front end and secure it with jack stands. Please refer to the article on jacking up your car. The power steering fluid should be syphoned from the reservoir.

Before you do any work on your car it is important that you wear safety glasses and work gloves. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. Never work on your vehicle if you feel the task is beyond your ability. Always disconnect the battery before working on your car.

Using a 17mm and 22mm open ended wrench, loosen the two fluid lines leading to the steering gearbox.
Figure 1

Using a 17mm and 22mm open ended wrench, loosen the two fluid lines leading to the steering gearbox. You should have a proper oil receiving receptacle under the steering gearbox to catch the fluid.  

The lines may take some force to loosen.
Figure 2

The lines may take some force to loosen. A 22mm open end wrench can be substituted with a 22mm crow's foot with a socket. 

Using a 10mm socket, unscrew the pinch bolts at the base of the steering column.
Figure 3

Using a 10mm socket, unscrew the pinch bolts at the base of the steering column.

Lift and support the front axle of the vehicle.
Figure 4

Lift and support the front axle of the vehicle. Place a jack stand under the lower control arm. You have to remove the tires to perform this job, which makes access much easier since you may not have the use of an automotive lift. See our tech article on jacking and supporting your vehicle and removing the front tires. 

I placed a jack stand under the chassis as well.
Figure 5

I placed a jack stand under the chassis as well. The procedure to replace the front sway bar bushings is the same for both the left and right sides. These pictures are of the passenger side of the vehicle. It is recommended you replace both sides at the same time to keep your handling neutral. Placing a jack stand under the chassis provides additional safety.

The drag ling has a crown bolt with a cotter pin attached.
Figure 6

The drag ling has a crown bolt with a cotter pin attached. There may be a layer of grease or debris covering it. In order to get at the cotter pin you may have to wash off the grease or debris.

Using needle nose pliers straighten the cotter pin and pull it through the crown bolt.
Figure 7

Using needle nose pliers straighten the cotter pin and pull it through the crown bolt.

Using a 17mm socket, loosen and remove the crown bolt that holds the drag link.
Figure 8

Using a 17mm socket, loosen and remove the crown bolt that holds the drag link. The drag link and bushings are now free to be removed

The tie rod will have to be removed as well.
Figure 9

The tie rod will have to be removed as well. It is connected with a crown bolt held in place with a cotter pin. 

Using a pair of needle nose pliers, remove the cotter pin.
Figure 10

Using a pair of needle nose pliers, remove the cotter pin.

Using a 17mm wrench, loosen and remove the crown bolt.
Figure 11

Using a 17mm wrench, loosen and remove the crown bolt.

Using a separating tool, apply slow pressure to remove the connecting bolt.
Figure 12

Using a separating tool, apply slow pressure to remove the connecting bolt.

In order to remove the steering gearbox the exhaust line has to be removed.
Figure 13

In order to remove the steering gearbox the exhaust line has to be removed. Use a 12mm and 13mm wrench and socket to loosen and remove the exhaust line under the steering box.

Use a 12mm and 13mm wrench and socket to loosen and remove the exhaust line on the other side.
Figure 14

Use a 12mm and 13mm wrench and socket to loosen and remove the exhaust line on the other side. 

Using a 13mm socket, loosen the bolts holding the steering gearbox to the frame.
Figure 15

Using a 13mm socket, loosen the bolts holding the steering gearbox to the frame. There might be residual fluid in the steering gearbox. Remove the bolts from the frame and lower the steering gearbox from the splines of the steering shaft.
When installing the steering gearbox, guide the steering shaft splines onto the coupling as you raise the steering box into position. 
If you decide to realign your wheels, the following are the specifications:

Camber (degrees): 0 degree +10' -20'
Caster (degree): 3 degree 40'; +/-20'
Toe-in (in): 0.04 - 0.12



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Comments and Suggestions:
turbosube Comments: Would the quicker ratio box out of the 560 sl interchange with the box in a 73 450 SLC? Thsnks
May 28, 2016
  Followup from the Pelican Staff: I don't believe so. - Nick at Pelican Parts  
Kevin Comments: I have a 1973 R 107 , 450 SL, need to adjust Steering box do I turn Adjusting screw clockwise , or, Anti Clockwise Kevin
March 18, 2016
  Followup from the Pelican Staff: Depends on if you are tightening or loosening. When adjusting the worm gear that way, just do 1/8 turns at a time, clockwise should tighten the steering. Too far, the steering will bind once you get driving. Be sure you follow factory repair instructions when performing this procedure. - Nick at Pelican Parts  

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Page last updated: Mon 12/5/2016 02:53:38 AM