Rear sub frame urethane bushing
 

97 318ti with 200k miles

Looking for brand recommendations for a non-squeaking urethane bushing with a softer (daily driving use) vibration (75A?). Also, since labor is up to 90% the cost of this service what else should I look to take care of while the differential, etc, is out? In other words, is it worth it to do the differential mount and rear trailing arms as well even if they are in decent condition.

My plan is to keep the car for five years and I bought it 18 months ago.

I've been running Powerflex street bushings in my subframe for a few years now and have been happy with them. No squeaking, just make sure to apply a liberal amount of the grease they supply. I'd do the RTABs as well while they're out. Diff, maybe. I did, but it seems easy enough to get to at some other point if it's in decent shape now.

STOCK!

Yeah, I'll do the RTABs and the diff probably too as I don't know it's condition, it will be an upgrade, it will be cost effective, and I can forget about it.

Thanks for the feedback on Powerflex.

Anybody out there use Revshift? They're almost half the cost but the low profile is a concern.

I'm about to put some AKG Motorsports Street/ Race bushings in with an LSD swap. I'll let you know my initial thoughts

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Thanks

Unless you are seriously tracking your car, OE bushings are just fine. If you want to upgrade, get OE bushings for an M-coupe.

Unless you are seriously tracking your car, OE bushings are just fine. If you want to upgrade, get OE bushings for an M-coupe.

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The problem with OE's is that I'll be kicking myself down the road if I throw another $1K plus for a manufacturer's planned obsolescence when I could've resolved it for posterity while improving the handling.

Are the M-coupe's comparably priced?

Last week did subframe and RTAB with Ireland Engineering urethane. Did without any of the proper tools and left trailing arms on car. Was a complete pita but did it. What tools do you have? Get the AKG bushing removal tool, it's $35 or make your own. There is a noticeable increase in noise and handling. If you want quiet get stock. Only reason I changed to urethane is for motor swap.

Yes, the m-coupe bushings are very reasonable. I've been tracking for 2 years with those and they are fine...

A serious point to make is that if you are going to upgrade the bushings on one of the rear suspension components, you should do them all with comparable bushings... i.e., don't just do the subframe bushings, do the RTABS and Diff with something similar... Otherwise you end up putting undue stress on other components..

I did a 1988 325iX rear-suspension rebuild last winter: it is absolutely identical to the 318ti rear suspension. I went with PowerFlex subframe bushings, Trailing Arm Bushings, and a Rear Diff Bushing. I dropped the entire rear subframe, rolled it out, and then cleaned painted everything and replaced the bushings.

I do not believe that the noise/vibration/harshness has deteriorated at all, but I do realize that can be very subjective with some people having a more sensitive ear than others.

The biggest challenge we had was that the OEM subframe bushings were absolutely corroded into the body due to 27 years and 150,000 miles of driving in salty environments (first Chicago and then Pittsburgh). On the E30 forums, the general conclusion is that with cars that have never seen salt, are relatively easy to do, while any significant salt exposure can lead to one HORRIBLE job. We fiddled around for nearly 3 days before figuring out how to get them out. I can provide more details if anyone is interested. The fundamental issue is a bad design by BMW: the inner "sleeve" of the bushing is aluminum, while the cavity in the body that the bushing sleeve presses into is steel. When these cars were built, no grease was used when pressing the bushings into the body. Steel + Aluminum+ Salt led to serious galvanic corrosion, where essentially the bushing is "welded" to the body.

ptbowman, I know this is an old post, but can you share how you got the original aluminum sleeve off the steel stud on the rear subframe?

Did you have to spray a lot of PB Blaster to get it unstuck? Did you heat it up with a propane torch?
Let me know if you don't mind.

Heat and air hammer worked for mine. Not as stuck but worked

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It was a PAIN!!!! I have worked on cars for decades- biggest pig of a job I have ever seen. I tried do many different things that just didn't work. Lots of penetrating oil (even stuff better than PB Blaster) did not work. There is just no good way to get the fluid in thst aluminum/steel interface. Finally I went crazy with a drill. First I drilled multiple holes around the circumference of the rubber bushing in order to separate that from the inner aluminum sleeve. I then carefully cut away the rubber bits from the aluminum sleeve. I was hoping to grab the aluminum sleeve with a giant visegrip hoping that torque would break the corrosion. Nope! So finally I bought a series of drill bits and very carefully enlarged the center hole in the aluminum sleeve until it was thin enough that it literally fell out of the body. My sons and I were whooping and hollering and high-fiving because we had been fighting this for days- my wife came running to the garage thinking someone was hurt! We did not use a torch because I was really concerned about the gas tank being so close to everything and the last thing I wanted was a gasoline explosion especially in a garage integral to the house. We could have probably rigged some heat shields but I just didn't want a hot flame within inches of a gas tank And fuel lines in adfition, a flame will definitely set the rubber bushing on fire creating a hortible smoky mess. In hindsight I could gave done this in an hour by just drilling out the aluminum sleeve and not messing around with everything else I tried. 20/20 hindsight. BUT be incredibly careful NOT to damage the bushing locating point in the body (the steel sleeve that locates the aluminum sleeve). If you mess up the steel sleeve you'retotally screwed! It wasn't that hard though- the aluminum is soft and the drlll bits cut easily through it. Run a slow drill speed and go slowly, frequently stopping to check your work. No problem on first few bits but that last where you have thinned the aluminum sleeve enough that it loses all strength- BE CAREFUL