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Drive Shaft Bearing Replacement
 
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Pelican Technical Article:

Drive Shaft Bearing Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$13 to $30

Talent:

**

Tools:

46mm, 41mm wrench, 13mm socket, three arm puller

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Drive shaft bearing

Hot Tip:

Use the right wrenches

Performance Gain:

Get all the power to the ground

Complementary Modification:

Check your transmission mount

The drive shaft support bearing is between the front section of the drive shaft and the rear. This bearing helps support the weight of the shaft and keeps the drive shaft in alignment. When the bearing starts to go bad you will notice an increase in noise from the drive train and if it gets really bad you will start to hear a clunking sound as the drive shaft moves around within the bearing housing. These bearings should be inspected once a year and replaced at the first sign of trouble. Driving with a failed bearing will lead to an imbalanced drive shaft and this will lead to undo stress and wear on other components like the flex disks.

While you should always inspect the flex disks while inspecting the bearing, if your bearing has gone bad make sure to inspect the flex disks carefully as they are the first thing to fail with an unbalanced shaft. If your flex disks are good there is no need to replace them but please be aware that Mercedes considers the hardware on the disk to be single use only and you will be disconnecting the disks to replace the bearing.

There is not a lot of room to work in the tunnel under the vehicle and depending on how yours is optioned there can be several other components that make it even a tighter fit. While it is possible to remove the entire drive shaft assembly as one piece it can really add time to the job as you move things out of the way. If you have the right tools, which is a 41mm and 46mm wrench the job is easy, but you will not be able to get two large adjustable wrenches in the space. Do the right thing and borrow, buy or rent the wrenches for this job.

To change the drive shaft support you will need to safely raise and support the vehicle. Please see our article on safely raising and supporting your W123.

Before you begin removing things make sure to mark the relationship between the two sections of the drive shaft (yellow arrows).
Figure 1

Before you begin removing things make sure to mark the relationship between the two sections of the drive shaft (yellow arrows). These shafts come balanced from the factory and it is important that they go back together in the same aspects that they came apart. If you are reusing your flex disks make sure to mark their relation to the drive shaft as well.

Remove both the front and rear flex disks.
Figure 2

Remove both the front and rear flex disks. Please see our article on flex disk replacement for step by step instructions

Here are the two wrenches you will need; they are a 41mm and 46mm.
Figure 3

Here are the two wrenches you will need; they are a 41mm and 46mm. There is no way you are going to get two large adjustable wrenches in the tunnel so rent, beg, borrow or buy these wrenches to make the job easier. The only other option is to remove the shaft as one piece and depending on your vehicle that can be a pain.

Use the wrenches and separate the 46mm nut (yellow arrow) from the shaft (red arrow).
Figure 4

Use the wrenches and separate the 46mm nut (yellow arrow) from the shaft (red arrow).

You should be able to compress the shaft and remove the font section, if you are having problems use a 13mm socket and remove the mounting bracket and bearing (red arrows).
Figure 5

You should be able to compress the shaft and remove the font section, if you are having problems use a 13mm socket and remove the mounting bracket and bearing (red arrows).

Figure 6

Here is the front shaft out of the vehicle

Remove the bearing bracket and remove the rear shaft, once you get it on the ground remove the circlip (red arrow).
Figure 7

Remove the bearing bracket and remove the rear shaft, once you get it on the ground remove the circlip (red arrow).

Depending on how bad your bearing is will depend on how much you need to pull off.
Figure 8

Depending on how bad your bearing is will depend on how much you need to pull off. Use a three arm puller and make sure you get all of the old bearing removed.

Lube the new bearing with some dish soap and press the new bearing into the bracket.
Figure 9

Lube the new bearing with some dish soap and press the new bearing into the bracket.

Install the bracket and bearing back onto the shaft making sure that the shoulder of the bracket is facing the rear of the vehicle and don't forget to install the circlip.
Figure 10

Install the bracket and bearing back onto the shaft making sure that the shoulder of the bracket is facing the rear of the vehicle and don't forget to install the circlip. Installation is the reverse of removal.

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