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Discussion Starter #1
Hi everyone,

Going to be getting my subframe reinforced in the spring and was wondering if anyone here is running poly diff bushings. If you are, what bushings are you running and hows the NVH?

Thanks in advance!
 

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Anything harder than stock OE rubber will have NVH when it comes to diff bushings. You will need to either accept it (for performance reasons) or stick with a stock bushing. If you accept the noise just get a solid bushing set instead to get zero play.
 

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Discussion Starter #3
Anything harder than stock OE rubber will have NVH when it comes to diff bushings. You will need to either accept it (for performance reasons) or stick with a stock bushing. If you accept the noise just get a solid bushing set instead to get zero play.
I've heard mixed reviews about this. Rogue Engineering and Revshift for example are claiming no NVH from their poly bushings. Was hoping to see if anyone had them installed and would chime in on their experiences.
 

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Yeah a race shop I was talking to recommended solid/poly for subframe as OEM is too soft and then stick with OEM for diff, so you don't get NVH from diff
 
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Hi everyone,

Going to be getting my subframe reinforced in the spring and was wondering if anyone here is running poly diff bushings. If you are, what bushings are you running and hows the NVH?

Thanks in advance!
I used the ECS tuning poly diff bushings, only difference i noticed was at idle my steering wheel has a very tiny vibration to it. Car does feel more responsive when putting the pedal down, like a more immediate reaction but who knows i get all excited with new parts and it’s probably all in my head. Either way i have nothing bad to say about them.
 

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I used the ECS tuning poly diff bushings, only difference i noticed was at idle my steering wheel has a very tiny vibration to it. Car does feel more responsive when putting the pedal down, like a more immediate reaction but who knows i get all excited with new parts and it’s probably all in my head. Either way i have nothing bad to say about them.
I know this was posted in the M3 section, but for a non-M I'd have to strongly disagree. Maybe I got one from a bad batch but the bushing kept slipping fowards, which pushed the bolt head to be basically touching the aluminium bracket that goes around driveshaft by the diff. So basically the bushing was doing nothing and I was getting what sounded like a loud scraping noise, when it was just the diff vibrations transferring directly to the chassis through that bolt.

My solution was to hammer a thick flathead to space it out, then squeeze seam sealer I had on hand which solved the issue.

 

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I know this was posted in the M3 section, but for a non-M I'd have to strongly disagree. Maybe I got one from a bad batch but the bushing kept slipping fowards, which pushed the bolt head to be basically touching the aluminium bracket that goes around driveshaft by the diff. So basically the bushing was doing nothing and I was getting what sounded like a loud scraping noise, when it was just the diff vibrations transferring directly to the chassis through that bolt.

My solution was to hammer a thick flathead to space it out, then squeeze seam sealer I had on hand which solved the issue.

Hm, i’m not sure. I’ve put ~1000 miles on mine and they haven’t moved
 

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I wished for stiffer bushings but because of the weak floor it didn't make sense to me, wouldn't you want more amortization for the forces that tore the floor the first time?
 

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I wished for stiffer bushings but because of the weak floor it didn't make sense to me, wouldn't you want more amortization for the forces that tore the floor the first time?
I believe OEM bushings cause too much flex in the rear subframe putting force on the mounting points, where as stiffer bushings reduce that flex. But as they wear out, they cause more damage to the subframe. I Could be wrong.
 

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Are we thinking poly didn’t exist when BMW designed the car and that’s why they didn’t use it? Did it exist but cost too much? Are they just wrong? Or did they make a decision for longevity or comfort over stiffness? It seems to me how you think about those questions determines which direction you go with this. You might prefer stiffness and recognize it comes at the expense of both comfort and longevity, for instance. But at least it’s a knowing decision.

I recently got new diff bushings, and told my guys to go with poly, to which they responded “absolutely not, you’ll hate it.” Then I told them about the E36 bushings working in this car. I forget where we ended up but they didn’t want to get a whole diff cover. Seems people always conclude poly gives too much NVH for questionable benefit, which is probably the same thing BMW M decided originally.

My $.02

maw

PS I ended up with an E46M front bushing and E36 rear bushings
 

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Hi everyone,

Going to be getting my subframe reinforced in the spring and was wondering if anyone here is running poly diff bushings. If you are, what bushings are you running and hows the NVH?

Thanks in advance!
I made an account just so I could I share my experience with you on this topic. Many other users have past experience with poly or solid diff bushings COMBINED with other poly or solid components such as also having solid subframe or motor/tranny mounts..

Recently after I bought my e46 m3 I notice a vibration at 2k rpm (and only at 2k rpm) along with a slight clunk/thud under hard acceleration. Very common in these models and some people will even tell you this is the "M Clunk". Anyway, my first thought was to change the Guibo or Flex disc along with center support bracket etc. I did this and it helped but did not completely solve the vibration and clunk..

I went back to my local shop and asked them take photos of diff bushing for me, sure enough they were pretty worn! Still driveable but worn enough to cause the slight vibration and clunk but only under hard acceleration. NOW, onto the purpose of this background information: I ordered the Revshift 80a poly bushings which they describe as an OEM plus+ feel as they are slightly stiffer than OEM, but not as stiff as many of the other brands that use 95A or 75D.

the Revshift 80a bushing COMPLETELY got rid of the vibration and the slight clunk. Both are completely GONE. I have no diff whine whatsoever no vibrations no squeaking at all (I have now had the bushings in for a week). Everything in my drive line is completely stock besides the diff bushings. Maybe this is why I don't have any NVH? I dont know if you have any other poly or solid components in your driveline or suspension but just know that if you are completely stock down there and you add quality 80a diff bushings, you should see little to ZERO NVH considering your car is in good condition. Also this information is not outdated and no other weird variables playing into it - like is said my car was 100% stock and I added the 80a diff bushings and it was perfect. Couldn't be more happy with them. I could make in cabin video for you if you needed heck i would even let you drive my car for yourself if you are in the PNW.

Anyway, just wanted to make sure you had accurate information from someone that specifically has poly 80a diff bushing with no other driveline modifications.
 

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These people seem to cover the issue pretty well in the E30 space, and may even sell a kit for the E46M. See here... https://www.garagistic.com/collections/e46-performance-parts?sort_by=price-descending

Until this thread, I didn't know there were different stiffnesses of Poly, but of course it makes sense.

Cheers,

maw
 

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when my mechanic did the reinforcement weld he recommended Poly rear subframe bushing and OEM Diff bushing, sorry I forgot what Duro..I think is the lower one. not too much NVH in the cabin, just from my experience, I do not track the car.

I did have the 80A diff bushing in my WRX before I do feel more vibration thru the shifter and in the cabin
 

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Discussion Starter #15
I made an account just so I could I share my experience with you on this topic. Many other users have past experience with poly or solid diff bushings COMBINED with other poly or solid components such as also having solid subframe or motor/tranny mounts..

Recently after I bought my e46 m3 I notice a vibration at 2k rpm (and only at 2k rpm) along with a slight clunk/thud under hard acceleration. Very common in these models and some people will even tell you this is the "M Clunk". Anyway, my first thought was to change the Guibo or Flex disc along with center support bracket etc. I did this and it helped but did not completely solve the vibration and clunk..

I went back to my local shop and asked them take photos of diff bushing for me, sure enough they were pretty worn! Still driveable but worn enough to cause the slight vibration and clunk but only under hard acceleration. NOW, onto the purpose of this background information: I ordered the Revshift 80a poly bushings which they describe as an OEM plus+ feel as they are slightly stiffer than OEM, but not as stiff as many of the other brands that use 95A or 75D.

the Revshift 80a bushing COMPLETELY got rid of the vibration and the slight clunk. Both are completely GONE. I have no diff whine whatsoever no vibrations no squeaking at all (I have now had the bushings in for a week). Everything in my drive line is completely stock besides the diff bushings. Maybe this is why I don't have any NVH? I dont know if you have any other poly or solid components in your driveline or suspension but just know that if you are completely stock down there and you add quality 80a diff bushings, you should see little to ZERO NVH considering your car is in good condition. Also this information is not outdated and no other weird variables playing into it - like is said my car was 100% stock and I added the 80a diff bushings and it was perfect. Couldn't be more happy with them. I could make in cabin video for you if you needed heck i would even let you drive my car for yourself if you are in the PNW.

Anyway, just wanted to make sure you had accurate information from someone that specifically has poly 80a diff bushing with no other driveline modifications.
Thank you for this! This is what I was hoping to hear. I was really leaning toward the revshift 80A bushing, glad to hear it doesn't add any NVH.

From what I've been reading, subframe bushings (no matter poly or solid) won't add any significant NVH.
 

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Thank you for this! This is what I was hoping to hear. I was really leaning toward the revshift 80A bushing, glad to hear it doesn't add any NVH.

From what I've been reading, subframe bushings (no matter poly or solid) won't add any significant NVH.
No sweat haha trust me I was looking for same thing! I’m glad I could help. Feel free to message me with any questions

side note - to the OP above that mentioned the 80a diff mounts on their Subaru WRX (with all due respect). Adding that you felt increase in NVH in a completely different vehicle only adds to confusion for the ops question. The fact that they were used on an entirely different car is a huge variable as well as we don’t know what other mods were on that car. None the less, two separate Cars. Again, not trying to harp on you! Just helping the OP make the right choice with the most accurate information
919226
 

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Haha sorry my bad 😀
 
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