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Pelican Technical Article:

Driveshaft Removal

Tom Morr

Time:

3 hours3 hrs

Tab:

$71.00-$118.00 (per flex disc, if needed)

Talent:

**

Tools:

Floor jack, torque wrench, ratchet, sockets, wrenches, extensions, 10mm hex bit, T50 Torx bit, pry bar(s)

Applicable Models:

Mercedes-Benz SLK230 (1998-04)

Parts Required:

Replacement flex disc coupling

Hot Tip:

Lower the exhaust as far as it can safely go.

Performance Gain:

Corrects driveline clunks and vibration.

Complementary Modification:

Replace rear flex coupling disc, inspect the transmission mount, exhaust, and driveshaft, repair or replace components as necessary.

Driveshaft (aka propeller shaft) vibrations make motoring annoying. Vibrations that transmit into the interior: especially at the rear console section: and hard shifting between gears are prominent symptoms of a driveshaft problem. The R170 SLK has a two-piece driveshaft that couples to the transmission and rear axle with rubber flex discs. These discs crack and wear. They're the most-likely sources of driveline vibration and noise.

A separate article details the process for rear flex-disc replacement. The flex discs can be replaced with the driveshaft in the car: The shaft collapses far enough at its slip joint for the flex discs to be removed and replaced on the car. The rear flex disc is exposed and easy to inspect visually. The front disc is obscured by the transmission crossmember and mount, which must be removed in order to inspect the disc.

The intermediate bearing is another vital driveshaft part that eventually wears out. The grease of the sealed bearing eventually breaks down, causing the bearing to squeal and eventually seize if ignored. The bearing is suspended in a rubber bushing, which also has a limited service life -- the rubber dries out, cracks, and no longer adequately supports the intermediate bearing.

One possible diagnostic tool is mounting an action camera under the car, clear of moving parts. Focusing it on the intermediate bearing and filming while driving can generate footage that either exonerates or convicts the bearing. For additional information, see the article dedicated to bearing replacement:

http://www.peachparts.com/Wikka/W123DriveShaftSupportBearing

The driveshaft's U-joint is also sealed. It will eventually dry out and need to be replaced. The driveshaft's centering sleeves can also wear at their sealing lips. Replacement sleeves are available.

The bulk of the wear parts are in the rear half of the driveshaft. If the front flex disc is still good, time can be saved by removing only the rear half of the driveshaft. Three or four bolts (depending on model) secure the driveshaft and rear flex disc to the rear differential; two 13mm-headed bolts mount the intermediate bearing on the car. On some cars, a 41mm open-end wrench is required to loosen a nut on the driveshaft's slip joint. Our project car, a 2000 SLK 230, didn't have this nut.

Some SLK owners might opt to save troubleshooting/servicing time by replacing the entire driveshaft with a rebuilt one. (A troubleshooting overview is provided here.) The R&R job can be done at home, with the car raised and secured on jack stands or ramps. A few components must be removed and others must be lowered, but it is a viable one-person job. Time-wise, setting aside a day provides some margin of error.

Separate articles cover transmission mount removal and rear flex disc replacement. Leaving the flex discs on the driveshaft saves time. Also, the left rear cross-brace must be removed with a T50 Torx bit. This creates clearance so the exhaust can be lowered far enough for the driveshaft to be removed from the rear axle end.

Tips

Accumulate the specialized tools ahead of time to make your job easier. The flex discs might have bolts with 10mm or 12mm internal hex heads. Check the driveshaft for a 41mm clamping nut just upstream of the intermediate bearing. The MB part numbers for the special open-end wrenches are 126 589 00 01 00 and 201 589 00 01 00.

To help separate the flex discs from the driveshaft (see the Rear Flex Disc replacement article for details), we used a pry bar and a large screwdriver.

New flex disc kits typically come with new hardware, which is good since the flex disc hardware is one-use-only and should be replaced whenever removed.

The driveshaft is balanced to minimize vibration as it spins. Either make reference marks before removing the driveshaft or run a piece of tape the length of the tube so that the halves can be reassembled in the exact same position.

Torque Specs:

Flex disc, 10mm internal hex head: 40 Nm / 30 ft-lb

Flex disc, 12mm internal head: 60 Nm / 44 ft-lb

Intermediate bearing to car: 25 Nm / 18 ft-lb (with washer), 30 Nm / 22 ft-lb (with collar)

Transmission crossmember: 60 Nm / 44 ft-lb

Front reinforcement brace: 20 Nm / 15 ft-lb

Rear transverse bridge: 20 Nm / 15 ft-lb

With the car raised and secured with jackstands, the transmission needs to be supported.
Figure 1

With the car raised and secured with jackstands, the transmission needs to be supported. The bellhousing is a good spot to put a jack. Less ideal on cars with automatic transmissions is the transmission pan, with the load spread by a piece of wood. The transmission crossmember comes off with six 17mm-headed bolts (green arrows). Two 13mm bolt (purple arrows) mate the crossmember to the transmission mount.

Next, the exhaust must be loosened.
Figure 2

Next, the exhaust must be loosened. Unhook the hanger in front of the rear axle (green arrow) and unbolt the ground strap (purple arrow).

The muffler's weight needs to be supported after its two rubber hangers are slid off the mounting ears (purple arrows).
Figure 3

The muffler's weight needs to be supported after its two rubber hangers are slid off the mounting ears (purple arrows). Another ground strap must also be unbolted (green arrow).

The heat shield comes off next.
Figure 4

The heat shield comes off next. Four 8mm nuts hold it on body studs. The shield is flexible and can be bent to slide out sideways between the exhaust and body.

Unplug the after-cat oxygen sensor.
Figure 5

Unplug the after-cat oxygen sensor.

Next off is the rear transverse bridge, located aft of the driveshaft's intermediate bearing.
Figure 6

Next off is the rear transverse bridge, located aft of the driveshaft's intermediate bearing. One of its four 13mm-head bolts also mounts the O2 sensor bracket (arrow). Also visible is a piece of masking tape used to index the driveshaft so its halves can be re-aligned later. You should be able to see the bottom edge of the masking tape along the right side of the driveshaft.

The reinforcement brace is removed next.
Figure 7

The reinforcement brace is removed next. It's above the catalytic converters, held on by four 13mm bolts.

Make sure that the muffler is supported, then remove the two 13mm-head bolts (purple arrows) that secure the exhaust to the car upstream of the cats.
Figure 8

Make sure that the muffler is supported, then remove the two 13mm-head bolts (purple arrows) that secure the exhaust to the car upstream of the cats. The transmission mount removes by taking out two 16mm bolts (green arrows).

If the driveshaft has a clamping nut between the rubber boot and intermediate bearing, back it off a turn.
Figure 9

If the driveshaft has a clamping nut between the rubber boot and intermediate bearing, back it off a turn. Then loosen the two 13mm bolts that secure the intermediate bearing to the car (arrows).

If the front flex disc passes visual inspection, it can be left on the transmission.
Figure 10

If the front flex disc passes visual inspection, it can be left on the transmission. Otherwise, the flex disc can remain attached to the driveshaft. On this 2000 SLK with an automatic transmission, the flex disc bolts to the transmission with three bolts that have internal 10mm hex heads. The driveshaft is mated to the flex disc with three 19mm-head bolts. All six nuts, on the transmission side, are 19mm.

Unbolt the driveshaft from the rear axle.
Figure 11

Unbolt the driveshaft from the rear axle. Pry the flex disc away from the axle if necessary. Removing the intermediate bearing's bolts allows the driveshaft's rear half to be slid out past the axle and set aside.

Clearance is tight, but the driveshaft's front half can be shimmied out between the reinforcement brace's mounting bracket and the exhaust.
Figure 12

Clearance is tight, but the driveshaft's front half can be shimmied out between the reinforcement brace's mounting bracket and the exhaust.

The exhaust might need to be lowered carefully at the muffler until the driveshaft can be passed out the back.
Figure 13

The exhaust might need to be lowered carefully at the muffler until the driveshaft can be passed out the back.

The rubber boot slides onto the front half's tail end.
Figure 14

The rubber boot slides onto the front half's tail end. It protects the grease on the splines and should be replaced if the rubber is cracked.

The front flex disc can be changed with the driveshaft still in the car, but it's more accessible if the driveshaft has to come out anyway.
Figure 15

The front flex disc can be changed with the driveshaft still in the car, but it's more accessible if the driveshaft has to come out anyway.

This front flex disc has longer sleeves on the side that couples to the driveshaft.
Figure 16

This front flex disc has longer sleeves on the side that couples to the driveshaft. It might need to be pried out of the vibration damper.

The flex disc side gets a flat washer, whether it's on a bolt or a nut.
Figure 17

The flex disc side gets a flat washer, whether it's on a bolt or a nut.

The intermediate bearing should spin freely.
Figure 18

The intermediate bearing should spin freely. If it binds, squeaks, or grinds, its grease is probably dead -- the bearing should be replaced.

The rubber bushing around the intermediate bearing eventually gets old and cracks.
Figure 19

The rubber bushing around the intermediate bearing eventually gets old and cracks. A two-jaw puller is the cleanest way to remove the bushing and intermediate bearing.

Like the OEM M-B intermediate bearing, the driveshaft U-joint is sealed (non-greasable).
Figure 20

Like the OEM M-B intermediate bearing, the driveshaft U-joint is sealed (non-greasable). Cycle it through its range of motion to check for clicking, binding, or any other signs of non-smooth operation.

The driveshaft's centering sleeves also wear out over time.
Figure 21

The driveshaft's centering sleeves also wear out over time. The old sleeves can be pried out. The new sleeves are inserted to the same depth as the old ones.

Use M-B's long-life Molykote grease, or similar grease meeting NLGI Grade 2 spec, for the slip joint's splines.
Figure 22

Use M-B's long-life Molykote grease, or similar grease meeting NLGI Grade 2 spec, for the slip joint's splines. The splines should be reassembled in their original grooves so the driveshaft won't be out of balance.

For reinstallation, pack the driveshaft's centering sleeves with multi-purpose grease or coat the axle and transmission nubs, technically known as the
Figure 23

For reinstallation, pack the driveshaft's centering sleeves with multi-purpose grease or coat the axle and transmission nubs, technically known as the "centering spigots."

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