Powerflex diff bush problem

[KVF]

I recently installed the powerflex rear differential bushing during a complete suspension/bushing overhaul. I started to get some slight crackling/grinding noise sometimes when I was accelerating or decelerating; most frequently when I was cornering from a stop or if I backed off the gas hard after a corner. Sliding underneath the car to check things out everything seemed in order, other than the external washer on the powerflex rear diff bush. The most rearward washer had moved outside of the recessed portion of the bushing. It seemed that I didn’t torque the mounting bolt/nut sufficiently. I slid the washer out and it was slightly bent. I rectified the bend, slid it back in and made sure to get it seated within the recessed portion of the bushing, and applied a crap ton of torque to the mounting bolt. All seemed well on the test drive and throughout Sunday. However, 36 hours later on my way in to work, the noise has returned. Now as I sit and ponder WTF, I’m wondering if those large washers should be installed at all... Was I a total noob by installing them, and they are just supposed to be used to press the bushing into place? The box didn’t come with any instructions, and the installation seemed pretty straight forward to me. Any thoughts?

Thanks in advance for any insight.
K

[KVF]

No one else has had this issue with the powerflex bushing?? I jumped underneath after work yesterday and sure enough the washers had worked their way outside of the recessed portion of the bushing. The inner washer actually made a slit through the top of the bushing, so I'm really thinking I noobed it up and somehow installed these wrong. From the picture you'd assume that the washers mount inside the recess, but the more I think about it, it doesn't make sense as they obviously provide 0 flex. I have a message in to BW, so I hope to get some insight.

[Doughnut]

Excuse my ignorance, but ive never seen this style of diff bush before.

Looking at the picture I can only agree that it looks as though the large washers fit inside the recess's on the bush to hold the bush inside the diff cover.

Maybe the washers supplied are too flimsy for the job? I can't see how you could install that bush any other way.

Possible fix is to machine thicker washers for the same application?

This is just my opinion, Ive had no experience with this particular style of bush before. GL!

[KVF]

Thanks for the reply and insight. I just now received a response from BW, who confirmed that I had installed it correctly (just as you explained as well).

The issue is supposedly with the amount of torque applied. Just a bit too much and it doesn't allow the washers to properly slide up and down the bushing under acceleration/deceleration. However, I don't like the thought of the bush moving between the washers. As you can see from the picture, the washer has less than an 8th an inch of travel before it's trying to push through the little recessed lip. It's as if the diff shouldn't move at all. Once I bolt the bushing up and remove the jack from the diff, it immediately drops a bit and the washers are already pressing up trying to go through the lip... I apparently didn't do my homework well enough before this purchase. What's a good differential bushing for a street driven car?

[E30Gus]

I have the same bushing and the washers didn't really fit inside the poly very well at all. The washers ended up chewing up the outside lip of the poly. I believe that the washers are there to keep the poly bushing in place as without this the 2 pieces could possible come apart? I have had bad experiences with Power flex bushings and their quality. I will not buy their brand again.

[rav320uk]

I've had the same Poly bush on my diff for over 24mths now and no issuse.
One question I would ask is did you apply any lubricant to the bush before you fitted it?

[KVF]

I have the same bushing and the washers didn't really fit inside the poly very well at all. The washers ended up chewing up the outside lip of the poly. I believe that the washers are there to keep the poly bushing in place as without this the 2 pieces could possible come apart? I have had bad experiences with Power flex bushings and their quality. I will not buy their brand again.

Exactly. I don't think it's a huge issue, as the outerlip doesn't have anything to do with the bushings performance. However, it was pretty lame to see, and once it rips the washer can scrape the diff every now and again.

I've had the same Poly bush on my diff for over 24mths now and no issuse.
One question I would ask is did you apply any lubricant to the bush before you fitted it?

Yes, I did use the supplied lubricant. I think the issue lies in the subframe bushings. Are you running poly bushes within your subframe? I think that firmer subframe bushes will not allow as much flex to the diff bushings, thus keeping the washers movement just minimal enough to keep from ripping the outer ring. I'm personally running new rubber bushings in the subframe, so I think it's best that I look for some sort of solid rubber mount for the diff... Anyone have anything tried and true they'd like to suggest?

Thanks again for the replies.

[rav320uk]

Exactly. I don't think it's a huge issue, as the outerlip doesn't have anything to do with the bushings performance. However, it was pretty lame to see, and once it rips the washer can scrape the diff every now and again.



Yes, I did use the supplied lubricant. I think the issue lies in the subframe bushings. Are you running poly bushes within your subframe? I think that firmer subframe bushes will not allow as much flex to the diff bushings, thus keeping the washers movement just minimal enough to keep from ripping the outer ring. I'm personally running new rubber bushings in the subframe, so I think it's best that I look for some sort of solid rubber mount for the diff... Anyone have anything tried and true they'd like to suggest?

Thanks again for the replies.

There's your problem on the Diff mount, lubricant, get rid of any residue on the bush and the diff cover itself and refit the bush dry.
I have replaced every rubber mount on the car, rear sub, arbs, lollipops etc, these need to be lubricated.

Rav

[Doughnut]

What's a good differential bushing for a street driven car?

IMHO, stock is the best bushing for a street driven car.

If your poly bush is damaged already, order and install a stock rubber BMW bush.

There's your problem on the Diff mount, lubricant, get rid of any residue on the bush and the diff cover itself and refit the bush dry.

Rav

Interesting concept. OP, if you choose to do this go slow on reinstallation or risk further damage to the poly bush.

[KVF]

Thanks again for the replies & insight.

I will most likely go with a stock bushing, but it was my intial thought to have something a bit firmer than the webbed design. Maybe it's the case that all of the newly made bushings are indeed firmer than the older design.

I was going to try the grease free install, but everything BM has told me, along with my own observations of "this particular issue", tell me that a grease free install wouldn't help. In fact BM explained that the bushing is expected to move up/down between the washers. They explained that applying too little grease and/or applying too much torque (to the retaining bolt) will make the washer bind, bend, and create issues. I didn't use any grease on the face of the bushing, and I'm fairly certain I went over the 59 ft lbs of torque. I'll properly torque a new bolt/nut tonight and everntually get a new bushing in the upcoming week.

[36brua]

Good option to poly.
http://www.turnermotorsport.com/html...ID=33171134802

real OEM: 13 Rubber Mounting SOLID E30 325IX 33171134802

Be careful when pressing new bushing into the cover. It is a tight fit. the cast ing can break.

[KVF]

I searched around and couldn't find anyone else offering a "completely solid" rubber mount like the one Turner advertised. I didn't like the price, but decided to just bite the bullet and go for it. I had confirmed on the phone with them that it was completely solid (like it's pictured). However, what showed up to my house was the same exact bushing bav auto sells for half the price. I'll be on the phone to turner in a bit to rectify the situation. I've had good experiences with them in the past, so I hope this isn't going to be an issue. Pictured below is what showed up... Definitely NOT solid.

[36brua]

I searched around and couldn't find anyone else offering a "completely solid" rubber mount like the one Turner advertised. I didn't like the price, but decided to just bite the bullet and go for it. I had confirmed on the phone with them that it was completely solid (like it's pictured). However, what showed up to my house was the same exact bushing bav auto sells for half the price. I'll be on the phone to turner in a bit to rectify the situation. I've had good experiences with them in the past, so I hope this isn't going to be an issue. Pictured below is what showed up... Definitely NOT solid.

Ha I didn't like the price either but I bought it . what you received is not the 'solid' bushing. I've had it installed for a few months no problems, xtra noise, vibrations etc. GL

[KVF]

They sent me the correct one today. I forgot to snag a diff gasket though, so I may have to wait to do the install. Maybe I can get it down far enough to do it on the car...

BTW, the bush does install arrow facing upward correct?