Didn't know where to post this. Car is an E36 Chassis with an E30 rear end. In preparation for an upcoming DE I was bleeding brake fluid and noticed this. My left rear sub frame bushing has a rubber piece torn on the bottom. My right rear sub frame bushing has that same bottom rubber portion cracked. I'm guessing this might be contributing to excessive inside tire wear (in addition to the car being lowered) How critical is this? I want to replace them but would rather wait until my first DE of the new year.
Steven, looking closely at your picture, I'm not sure I see what you're referring to, or some part looking torn. Re-post the pic with an arrow, perhaps? Or a little more specific written description? Are those stock subframe bushings? I'm seeing some green there, making them look like Ireland Engineering urethane street subframe bushings. I'm not sure you should be seeing that much of the bottom of the bushing, it looks like they might not be fully into the sleeve. If they're urethane, it's possible you may need to further tighten the nut on the long bolt. Stock bushings are difficult to fully get inserted back into the sleeves, one time I had a shop replacing them and with every means at their disposal, were unable to get them fully inserted. Ireland's urethane mounts apparently install much more easily, when I had those installed they told me they installed a good bit more easily than stock rubber ones. However, they also increased the interior noise level, the rubber is better at isolating drivetrain and particularly differential noise - if you don't have urethane and are considering that route, be prepared for trade-off in noise increase. Inside-edge tire wear is a fact of life for track cars, obviously the negative camber that improves cornering performance means the edges are taking more wear when driving straight. I monitor that and have a tire shop flip the tires on the rims to even out the wear. If you suspect there's a problem, track cars aren't the ideal candidates for delaying maintenance. The entire rear suspension is located to the body by only 3 points - where the subframe points mount to the body, and the differential mounts to the body. If you have a problem develop, the last place you want it to happen is at speed on a racetrack where you might even be over 100 mph. An unexpected or sudden self-steering rear suspension due to some sort of subframe bushing problem, or worse, would be a bad thing at anytime never mind while on track. I have my E30 up in the air, I'll look at the subframe mount later on when I get a chance and compare what I see to your picture.
I took a photo of the right side too which would have shown what section is missing. Those are IE bushings. I understand now that some were defective several years ago. Maybe that's the case? Maybe it's just wear and tear. Literally. I've never seen the green portion until this weekend. That's definitely not normal. The bottom section should look like the top black section. The lower portion of the right side has a crack in the rubber. They are getting replaced. Don't know whether back to IE or stock. Need to look at my RTABs too. I just have no time to deal with this right now. I took another look at them today. There is a small pile of crumbled green stuff underneath my left subframe bushing. It is totally deteriorating.
Crumbling... sheesh! Besides reducing the flex-factor of the stock rubber, the other appealing aspect for urethane bushings I've always thought should be a longer service life than stock. Call Ireland and see what they have to say - looks like you have to replace them regardless. You can drop the whole rear relatively quickly as a piece, some hands would be helpful. It's a bit of a challenge to balance the diff, subframe, and trailing arms on a 4x4 or at least 2x4 to lower it once everything's removed and keep it all under control without it getting away from you until you have stuff down to ground level. If your brake lines from the trailing arms to the body aren't frozen up, the rest is pretty straightforward - Unbolt the shocks, the U-joint flange to the diff, (4 bolts I think), the 2 subframe bolts, and the bolt for the diff mount, and it's free, unless I'm forgetting something. A big project though, definitely would take some time.
Seems to be a known problem with the batch made at that time. Since they are crumbling I'm told they will be easy to remove at least. My problem is I only have a few days to get them and git er done. I'm going to have my indy shop do it hopefully while I'm away. Might as well change my RTABs too. They are just as old.
Maybe not a bad time for some new Redline diff fluid too, perhaps. Have your shop check the welds on the mounting ears on the subframe for the trailing arms. Quite awhile ago now, but I had this odd rear-steer problem, turned out the welds on the mounting tabs had cracked, and the trailing arms were shifting one way under braking and the other under power. Easy to look at and do something about when the subframe is out, or at least see if all looks copascetic.
