85 300D flex disc

[kolnerspieler]

Hi,

I need to replace the flex discs and 1 of my axles. I know that the drive shaft can be problematic to take apart when replacing the flex discs. Do I have to remove the drive axles completely, or can I just have it loose on both ends and sneak the discs in there.

[W124 E300D]

1/ chock both front wheels

2/ jack up one rear wheel so with the diff you can spin the whole thing and get to the nuts easier.

3/ rear donut is dead easy

4/ front donut pull the rear gbox mount and brace, you need to access to stop yourself damaging linkage or reverse cable etc.



The W124 has one at the front of the prop-​shaft just aft of the gearbox, and one at the rear, just forward of the diff, and also a centre bearing in the middle of the prop-​shaft with the UJ’s.

The first photo was taken by reaching under the car with a digital camera, because lacking a ramp and a work-​light you can’t see much under a car.

The photo confirms that the front flexi-​coupling is shot, note that the bolts are not centred in the rubber, and also note the broken rubber around the bolt.

To do this job you need to jack the front of the car up, I used a couple of car ramps, and then I used a 5 ton ratchet strap to secure the front wheels to the ramps… why will become obvious shortly.

First you have to drop the rear underbody plastic shroud, 8 mm socket will do the job.

Now the dog can see the rabbit, you will find that the flexi-​coupling is directly above the gearbox mount.

You need to remove this mount, two bolts 17 mm either side of the tunnel, and the two 13 mm bolts securing the mount bracket to the rubber mount itself.

Before you do this, use a scissor jack and a block of wood to support the rear of the gearbox. DO NOT JACK THE BOX SUMP, aft of the gearbox sump is the bracket that holds the exhaust, support the gearbox HERE only.

Once you have dropped this bracket you need a 19 mm ring spanner to undo the single bolt on top of the rubber mount, the rubber mount will then come away, exposing the coupling properly.

About 30 cm aft of the gearbox mount there is a piece of steel bridging the transmission tunnel, this is to stop the prop-​shaft dropping to the road if the front coupling separates, four 13 mm bolts remove this piece.

Now you can see what is going on, note very well the wire going into the rear of the gearbox on the left hand side, and the linkage on the right. If you didn’t remove the gearbox mount you couldn’t see this, and risk damaging it with a spanner, and causing yourself big problems.

Now, get an axle stand and jack up one rear wheel so that it is off the ground, place the axle stand under the rear jack point.

Now thanks to the diff you can rotate the prop-​shaft by hand to bring all 6 bolts in the flexi coupling around for access.

Naturally enough this means the transmission in neutral, and the parking brake released.

THIS is why you secure the front wheels to the ramps with 5 ton straps, you need to be absolutely CERTAIN that the car cannot roll, your life depends on it.

Now you undo all six flexi-​coupling bolts, 15 mm socket on the rear bolt head, 17 mm ring spanner on the nut at the front of the car.

Now you lever the prop-​shaft back along its splines until it is clear to drop. You may find that the steel inserts from the old flexi-​coupling remain stuck in either the gearbox or prop-​shaft, just use a ring spanner to pry them out.

You will want a sturdy flat blade screwdriver to separate the flexi-​coupling from the gearbox, and from the prop-​shaft.

The second photo shows the new part (£44 from GSF) on the left and the old part on the right. What you can’t tell from the photo is the new one is flexible, and the old one is a hard as wood.

Note well, the part numbers and writing which you can see here go towards the rear of the car.

Note also, the bolts all fit from the rear, and all the nuts go on the front.

If you look at the new one you will see that three of the holes in the new one have slightly proud sleeves, and the other three have slightly proud sleeves on the other side of the coupling.

It is most important that you mate these proud sleeves with the small recesses in the prop-​shaft, and gearbox respectively.

Then re-​assemble everything else in order, and job’s a good un.

[ImBroke]

Originally Posted by kolnerspieler

Hi,

I need to replace the flex discs and 1 of my axles. I know that the drive shaft can be problematic to take apart when replacing the flex discs. Do I have to remove the drive axles completely, or can I just have it loose on both ends and sneak the discs in there.

No need to remove the drive axles at all. As has been said, it helps to lower the trans some to better access the bolts for the front disc. The driveshaft will slide all the way out the back of the car. Make sure you mark the driveshaft when you separate the two halves if you're replacing the center support bearing. It just slides apart. The center bearing is probably shot as well. While I was at it, I'd do the trans mount also. I've done about 6 of these. Seems as if every 123 I buy needs both flex discs, center support bearing, and trans mount replaced.