Subframe mounts:
The front rear drivers side subframe mount on the S6 was totally shot and the rest of them were ancient so complete replacement of all mounts was necessary. Rather than replace them with new stock mounts we put in custom solid aluminum units.
Front mounts
Machined / welded solid aluminum. These things aren't ever going to move and will never need replacing. Subframe mounts are for weenies, most manufacturers simply bolt the subframe directly to the chassis.
The front side front mounts either slipped right in or needed some serious hammering to slide into the subframe. They always located perfectly to the bolt holes on the body, which was very nice. The old mounts had to be pressed out.
The front side rear mounts were quite difficult to line up properly. The next time we put them in we just bolted them to the subframe while it was still out of the car and used the three small bolts to bolt the it into the car. One hitch with these mounts, you need to use longer bolts to replace the six small bolts around those mounts. Be sure to order the four stretch bolts for the front four mounts from the dealer, they are impossible to find anywhere else. We put some steel nylock-nuts on the far side of the bolt coming out of the top of the mount for added insurance at 150mph.
The bolt through the shot front side rear mount on the drivers side was seized into the mount. We took the subframe out with the three bolts holding the mount to the chassis. Then we hacksawed through part of the mount to cut a relief for the threads. With vice grips, some PB blaster, and the proper socket we finally got the bolt out. Unfortunately we needed to reuse this single use bolt or we would have just cut it out. New bolts should be grade 10.9 minimum
Front rear subframe/control arm bolts(need two):
- N 904 563 02 M12x1.5x150x60 (150 long, 60 of it threaded)
Front front subframe bolts(need two):
- N 905 834 01 M12x1.5x105
Rear subframe mounts:
We took the subframe out, got off as much rust as was realistic, painted it, put in the mounts and stuck it back in.
New paint, new solid mounts, new nuts. We didn't have the rear differential mount or that would have been replaced at the same time. If your subframe was like ours I'd recommend cleaning, blasting, and repainting it. We did a hack paint job because of time constraints.
The old mounts were pretty shot. The slack in the rear drivetrain is noticeably reduced especially getting on and off of the throttle. I imagine with a new suspension and new differential mounts the difference would be even greater. The rear subframe is the attachment point for the rear differential mount, the rear outer control arm pickups, the rear upper suspension links and some misc. hard lines. Having the rear subframe solid in its place is vital to proper suspension geometry and drivetrain location/throttle execution.
other things to inspect/replace with this job
- differential mount
- rear camber links if the ball joint or bushing looks bad
- any rusty bolts etc.
- nuts holding the subframe onto the studs on the chassis.
