loose rearends revisited...

[Robert K]

Thought I'd post a followup to my post a few weeks ago about why E34 rearends seem loose. As a refresher, I took the rear controls arms off of my 1991 535i with the intentions of replacing the control arm bushings, the differential bushings, and the rear subframe mount bushing. To make a long story short, I really didn't feel there was anything wrong with the original bushings, so I put it all back together with the original bushings.

Immediately after that, I ordered a set of Bruno's subframe bushing inserts. These are essentially hard nylon washers that fit between the subframe bushings and the small plate that bolts to the bottom of the bolt that goes through the subframe bushings. Installing the inserts made a BIG difference. The car now seemed to respond to steering inputs as a whole. The rear end no longer felt like it was about a half step behind the front. I just got done putting new tie rod ends on the front end and having it aligned. Between the new tie rod ends and Bruno's inserts, my car really feels renewed. But I think the biggest difference came from the inserts.

BMW designed the subframe bushings to isolate the rear suspension from the chassis to provide a smooth ride. But I think they overdid the size of the bushings. The result is that the subframe can squirm around TOO much. Bruno's inserts limit the amount of travel the subframe can squirm around, thereby greatly improving the responsiveness of the rear end. However, I did pick up a bit of extra noise when the rear wheels encounter bumps, so I think a hard rubber or urethane would probably be a better material than the nylon-type material that Bruno uses. Those materials would still limit the movement of the subframe but still provide some isolation. I am going to be on the lookout for these materials and will make a set for myself to compare against Bruno's nylon ones. I've also read on this forum of persons filling new subframe bushings with some type of hard plastic or urethane before installing their new bushings. I also think that might be an excellent solution towards restricting the movement of the subframe.

So, there's what I've learned from this journey towards tightening up the rear end of my E34. I am so much happier with the way the car handles now. I hope this helps others out there who have similar problems.

Grace and peace,

Robert K
1991 535i

[Qube]

Nice writeup, and welcome to the stiffer side

Short plug regarding the inserts: http://www.bimmer.info/forum/showthread.php?t=24256

On that note, how were your diff bushings?

[Robert K]

I put a pry bar between the subframe and diff and could barely get any deflection. I tried it a couple of times and the diff appeared to be mounted very solidly. That's why I decided to just forget replacing the diff bushings.

Grace and peace,

Robert K
1991 535i

[Fred/Houston]

I put a pry bar between the subframe and diff and could barely get any deflection. I tried it a couple of times and the diff appeared to be mounted very solidly. That's why I decided to just forget replacing the diff bushings.

Grace and peace,

Robert K
1991 535i

Great nfo, did you do the work yourself or take it to a shop and how much was the cost? I need to get my rear "unclunked" as well.
Thanks
Fred/Houston

[Guapo]

We ave exactly the same issue in the 300ZX world. Silicone filled subframe bushings that fail over time. A couple of the vendors in the community designed aluminum spacers similar to the nylon ones for the E34:

[Robert K]

It actually depends on what work you want to do. If you're going to install Bruno's subframe inserts, it's a fairly simple job that can be done without even jacking the car up. If you're going to remove the trailing arms, it's a LOT of work! I did that work myself too, but it took about 5-6 hours and required a garage, floor jack, jack stands and lots of metric tools.

If you want to learn more about doing the subframe bushing inserts, check the link at Qube's post above. He shows exactly how to do it.

Grace and peace,

Robert K
1991 535i

[Tiger]

I am wondering... Have you guys ever replace your sway bar links? I got new links and Bruno's insert waiting to be installed. I will put in the links first and see how car responds before I install the inserts.

I just did my Mercedes sways... 205,000 miles on original links and sway bushing in front... Swapped it out and whoa... tight all over... and good. Huge difference.

[repenttokyo]

I'm replacing my front swaybar links tomorrow.