- 01/19/2015
- 1 Min Read
- By: Bryan McPhail
Mercedes S/E/R-Class Driveshaft Flex Joint & Transmission Mount Replacement
I recently wrote about checking driveline mounts and flex joints and the problems they can cause on a BMW, often starting as vibrations. This time let's look at the practicalities of swapping them out on the Mercedes W220 S-Class chassis. The procedure for E-Class and R-Class models is very similar.
Distribute the load with wood
If replacing the front flex joint (giubo) it's worth replacing the transmission mount at the same as you have to remove the transmission mount in order to get good access to the flex joint bolts. The first step is to support the weight of the transmission using a floor jack or trans jack underneath it. The Mercedes transmission pan seems to be a relatively weak point, (at least compared to the strong BMW/ZF pans!) so it's vital to distribute the load over as much area as possible with some wooden blocks. 10 to 12 inches square is about right (size of an old vinyl record). Just jack it enough that the trans raises a couple of millimeters so you know pressure is removed from the mount.
The mount is bolted to a cross member which then bolts to the chassis - loosen the two inner bolts first (13mm), then the outer 6 (16mm). The cross member can then be removed to reveal the mount & front flex joint. Remove the two bolts (16mm) connecting to the mount to the trans and the mount can be removed.
These cars have an open differential
Now the flex joint bolts can be removed - older cars may have 19mm bolts and nuts, newer ones may have Torx T60 bolts and 18mm nuts. You should have access to the lower 3 bolts without a problem but the driveshaft will need rotated to access the other 3. Because the driveshaft is balanced we want to be sure to reconnect it to the transmission exactly as we removed it, so this is a good time to paint some markings on the shaft and trans. At this point, unless you have a 4 post lift or used jackstands at all corners, you probably have the rear wheels firmly planted on the ground or ramp, so how do you rotate the driveshaft without moving the car? Well, these cars have an open differential - so if you put the transmission into neutral and jack one rear wheel whilst keeping the other firmly planted - spinning the raised wheel will rotate the driveshaft whilst applying no force to the planted wheel!
Orient the new part correctly
With all 6 bolts removed gently pry the driveshaft back from the flex joint, it should have at least an inch of travel available. You can now replace the flex joint with new - pay attention to the metal sleeves which protrude on alternate sides - these fit into recesses on the shaft and trans ends. In addition, note that bolts always face forward, and the washer always touches with the non-protruding end of the bolt sleeve (so washers alternate as you go around the disc). The flex disc is usually supplied with brand new bolts & nuts - as the nuts are of a locking type, never re-use the old ones.
Torque flex joint bolts to 60Nm. Reassembly of mount & cross member is opposite of disassembly. Mount & cross member bolts are all listed at 40Nm.
