It is an edited mirror of http://www.ottawa-vdubbing.com/forums/phpBB2/viewtopic.php?t=13397&start=0&postdays=0&postorder=asc&highlight=&sid=bba30212b7e6532f500c909c5c99dc40 . This writeup summarizes/rewrites/adds to the notes and edits the pictures.
The engine weight rests on 2 engine mounts. One is on the transmission and the other is under the power steering reservoir. The 3rd engine mount, the pendulum mount, aka, dogbone mount, lets the engine rotate a little bit while holding it steady. You may want to replace the dogbone mount for a variety of reasons. The most common ones are: you just installed a downpipe, and you're hearing a metal grinding/rubbing noise. You want to reduce wheelhop. A stiffer dogbone mount will reduce engine movement and will help reduce downpipe rubbing (the new bushings keep the engine from rotating as much) and reduce the possibility of wheelhop. The downside is that siffer engine mounts transmit more vibration and noise to the cabin.
You could buy an aftermarket dogbone bushing kit which includes only replacement bushings or a replacement OEM-stiffness dogbone. These are normally poly mounts which are harder than rubber mounts. Another option is the 034 motorsports mount sold by 034 motorsports. The blue mounts the author originally had were about 90 durometer, the yellow Forge ones are about 70 durometer, the 034 motorsports rubber dogbone is about 50 durometer. The stock dogbone mounts are about 40 durometer and all other mounts will cause some more noticeable vibration.
hydraulic jack and jack stands rated for your car
always replace bolts:
n 102 683 02 , n 905 970 05? or n 905 970 01? (long alignment plate bolt), n 102 466 03, available as a kit from ecstuning
Raise the car, make sure it's secure on the jack stands, apply the parking brake and chock the wheels, and make sure it's safe before getting underneath the car.
Use a hydraulic jack to support the transmission. This helps with alignment and reinstallation. Make sure it's not carrying the weight of the car since the jack stands should be supporting the car.
Remove the black alignment plate first (2x 16mm bolts), then remove the
dogbone mount (2x 13mm bolts).
If you are using a replacement dogbone then put the new dogbone on and see
the last picture for torque specs. If you are installing a bushing kit then remove
the 1x 16mm bolt compressing the bushings onto the dogbone.
The author used blue poly and yellow Forge bushings. Here is a comparison with the black stock bushings. The aftermarket ones are slightly taller than the black stock ones so you'll need to squeeze things together when you reassemble the mount. The author's comments on the blue bushings "The blue poly ones are stiffer than you could possibly imagine, and I wasn't even able to compress the 2 blue pieces into the dogbone mount. I ended up using the bigger blue bushing, and the smaller black stock bushing. This worked, but the car definitely gained some nasty interior vibrations." Yellow bushings "I ordered the Forge dogbone mount. They are softer than the poly ones (70 durometer rating) but definitely firmer than stock. The ride is beautiful! With my idle at 800rpm (more like 790), you can hardly tell a difference. You feel the engine a bit more, but it's definitely not intrusive. Plus, my wheelhop is almost completely gone (it's still there a wee little bit, but tonnes better than it was stock!). Also, my downpipe doesn't rub at all. If anything, I might loosen up the compression bolt to 10ft-lbs, just to smooth it out a little bit more."
On a diesel, I suspect that the idle roughness would be worse than on a
gasoline engine. In other words, I would choose a stock dogbone or 034
motorsports rubber dogbone mount. Even the 034 motorsports rubber mount
has been reported to give some additional vibration over stock since it's
harder. In addition, you shouldn't drive in a
manner to cause wheelhop. Wheelhop is when the tires quickly grip then let
go, in a bouncing motion. It's caused by a combination of suspension, tire
grip, and power. You can never power your way out of wheelhop so if you
feel the wheels bouncing up and down rapidly, get off the throttle since
wheelhop destroys drivetrains.
If they come with grease then lube up the bushing-metal contact areas. Put the smaller piece in first, and line up the 'grooves' in it with the ridges in the metal (the grooves go downwards).
There is a lopsided nut that goes into the end of the compression bolt. The lip on the edge of the head goes on the outside. If you put this nut in the other way, the compression bolt won't line up with the threads and it's not going to go in.
The compression bolt doesn't quite reach the little nut so you must squish the entire dogbone mount
and then turn the compression bolt to get the threads to catch. This might work better in a
vice but the author just used his body weight.
Torque the compression nut to 12ft-lbs, some blue loctite would help keep it
in place. Pictured below is the replacement with torque specs (they are
single use stretch bolts).
If you have any questions about the dogbone mount or would like opinions on aftermarket stiffer dogbone mounts, please ask in the forums here: myturbodiesel.com forums