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Discussion Starter #1
Hello all,

Recently came across subframe mount inserts on the Powerflex website and was wondering if anyone has tried these out?

BMW E39 540, M5 (96 - 04) Rear Subframe Mount Front Insert



I am trying to trace down and issue with my car and believe it is either the rear differential bushings / subframe bushings causing inconsistent shift quality. I can almost feel the drive line wind up and bounce/jerk on the 1-2 shift - makes the car very difficult to drive. I have to tread lightly when getting on the throttle in first gear and occasionally in higher gears.

I have replaced the front differential bushing (torn) with an OEM unit, Guibo, CSB, trans mounts (Rogue), and engine mounts and that did help but the issue is not fixed. Drive line feels extremely sensitive and lashy.

Was thinking of replacing all differential bushings with poly and then doing the inserts for the subframe as I find it hard to believe bushings of that size go bad at 70K miles..
 

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It is doubtful that those bushings are in bad shape, let alone damaged enough to be causing the problem you are having - the subframe would have to be almost disconnected from the car for it to be causing this problem.
 

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Agreed. I would be first looking at the driveshaft guibo/center support bearing and/or front diff bushing.
Those have all been replaced - read the first post.

Is this a throttle/tune issue or mechanical? Struts? video?

Don't believe its any of the items listed, although I have suspected the US throttle mapping. It has been much colder here lately, 47 degrees in the AM, on my 15 minute drive to work the drive train feels really solid for the first half leading me to believe it is the differential bushings. When they are colder they are essentially stiffer, as I drive the car I can start the feel the flex come back gradually. At least that is my current rationale.
 

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It is doubtful that those bushings are in bad shape, let alone damaged enough to be causing the problem you are having - the subframe would have to be almost disconnected from the car for it to be causing this problem.
Subframe bushings are probably fine. The diff bushings can and do fail. I had to replace mine at 90k miles. So far, no signs of failure with a fresh set of stock bushings.
 

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Bring this post back to get feedback on the subframe inserts...has anyone tried or have some knowledge on their application? Is this a simple pop-in with no need for bushing removal...do you recommend installing with existing/old bushings or should they be installed with new OEM bushings, etc.? If I have to remove the old bushings, I will probably go with the full bushings instead of the inserts...not scared of a harsh ride but I can't do vibration or noise.

Don't like the rear wheel steering feel I have been getting ever since ownership. I have replaced the rear ball joints and installed new shocks and springs (Koni w/DINAN)...helped a little but no where close to my old 530i sport. Car currently has 211k miles.

Thanks in advance for your insights.

Ken
 

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It looks like a band-aid to me. I would never try to reinforce an old bushing, I'd simply replace them. Now the inserts may make a difference on top of new bushings but I don't know.

We used to fill the empty spaces on M535i diff mount to shore it up a bit. I think it was a 60 or 70 durometer compound that you mix, pour, and let set for a day or two before installing. This would be much cheaper and more effective and you can select whatever durometer you choose. Check with McMaster or Grainger.

Good luck with your quest and keep us(me) updated. I'm always interested in the new paths owners forge.
 

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I just installed these with new subframe bushings and I'm loving them so far. They pop right in as you describe. If you look at a picture of the OEM bushing you can see that the open sections in the design only really allow for flex in one direction. The rubber is solid in the other. With the way the bushings go in the car, these inserts help to minimize the subframe movement from front to back. I find the car feels more stable under acceleration and braking. Overall there is no increase in NVH at all. The difference is very subtle. It's only once your really on it that you can tell it's stiffer. But that's ideal IMO.

That being said, if your subframe bushings are original with 211k miles on them they most definitely in need of replacement. Not only is the mileage high, the rubber is very old too. After debating between poly and OEM bushings myself, I'm glad I went the way I did. I think that these inserts or filling new bushings up like djazz suggested is an ideal approach for a car that's primarily driven on the street.
 

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Ok, great...that's kind of what I was thinking. Quick update on my rear wheel steer, I just picked up my car after getting new tires and an alignment and it now feels rock solid over bumps and cutting across lanes...no longer feels like the rear wheels are steering the back end. My rear tires were badly worn in the middle, almost bald but the outer and inner edges looked good with plant of tread. My tires were all at 36 psi so the pressure was not too high. I believe a bad alignment from the last NTB a few months ago may have been the culprit all along.

I will drop the subframe and install all new OEM bushings this summer...in the mean time I'll installed the inserts considering it is a simple pop in...can only help the old bushings for now. Thank you both for the feedback.
 

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I'm interested in how that works out without changing the bushings. I have the same rear wheel steering issue you have and although new tires and alignment masked the issue, the rear tires wore out very fast, within 10k miles on 45k mile tires. Alignment was good too, now that rear steering issue is back. I've changed all the bushings and new suspension. Only bushings I haven't touched are the subframes as everyone says they don't wear out. I have new ones on the shelf just no time to get them in atm.
 

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I'm interested in how that works out without changing the bushings. I have the same rear wheel steering issue you have and although new tires and alignment masked the issue, the rear tires wore out very fast, within 10k miles on 45k mile tires. Alignment was good too, now that rear steering issue is back. I've changed all the bushings and new suspension. Only bushings I haven't touched are the subframes as everyone says they don't wear out. I have new ones on the shelf just no time to get them in atm.

Sounds like you still have an alignment issue. I went through 3 alignments at 2 different shops before I was happy with the drive and tire wear. Ended up finding a shop that was willing to take the time to get it right. I also printed off the DINAN specs for them so that they could set-up their machine to those rather than what their machine was telling them to use for the E39 M5. Result is that the car drives great and tire wear is minimal.
 

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Nah, no alignment is going to keep your subframe from moving, cause that's what's happening. It's almost like a shudder. When hitting a bump I can feel the rear end pull in whichever side the bump was on. Essentially pulling in one direction and only the rear.
 

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Also, hope its not too off topic, but also interested in hearing from those who tried the Powerflex Subframe Bushings... not the inserts.

I heard several of my friends w/ E9x M3 are running solid subframe bushings (billet) w/o any negative results, and even heard some of the modern BMW's have solid too, no more bushings.

My Z3 had worn subframe bushings and felt like a snake going through turns... (rear wheels steering feel).
Threw on Ireland Engineering poly bushings and feels great now. nothing negative so far.

Normal driving on my M5 is fine, but taking corners faster, I can feel the rear being a little loose (sloppy).
 

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Don't know if this info will help, but if the sway bar bracket(s) is broken, the rear could feel wobbly.
 
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Did a rear end refresh end of last year with 3.62 gears and replaced the subframe and diff bushings at the same time. I did new Lemforder subframe bushings with Powerflex yellow (street) inserts. When I put the Lems in, I was surprised at how loose they still felt in the subframe when I stuck a big screwdriver through the mounting hole and wiggled it around. Dropped the poly inserts in and it stiffened up the movement a good 30-50%.

While the car tracks great and still rides relatively smooth, I can very slightly hear some diff whine now. At the same time, I installed 2 OEM rear diff bushings and solid aluminum (unicorn egg!) front mount. Jed says the mount shouldn't cause any whine to be noticeable, but I think I remember coming across a thread where someone was convinced it was the inserts.

All that said, I'm definitely happy with them and leaving them on. Luckily pulling them off (or installing) is easy and doesn't require removal of the subframe.
 

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I was very surprised at how easily the stock subframe bushings will flex. You can easily deflect them with one finger. Seems like a very bizarre choice of bushing for securing the entire rear suspension to the body of the car.

I'm going to give the inserts a shot. Since I'll be doing them with no other changes, I should be able to address whether or not they add any NVH

Thanks!
 
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