Hey All,
I'm getting my diff bushings changed out because they are worn out. I saw on AKG website that they recommend that the material matches the subframe bushings. Is there anything terrible that could happen if I left the subframe bushings as OEM?
Thanks!
If you increase the stiffness of one bushing it’ll have more affect on any weaker bushing thus prematurely wearing out your OEM bushings most likely.
98 M3 sedan
I would go much stiffer on the subframe and slightly stiffer in the diff. Like 75D subframe and 95A diff or 95A subframe and 80A diff.
I have 95A on both and I get some mild diff whine at certain RPM ranges. If I dropped one or the other down to 80A it would probably eliminate it. I think you can actually go as stiff as you want on one of them as long as the other is relatively soft like 80A or something, if you're still concerned with NVH. I'd also recommend the subframe be the stiffer of the two in order to minimize excess movement of the rear suspension, though it probably doesn't make a huge difference either way.
As to mixing OEM rubber and hard poly or solid mounts, I wouldn't suggest that for the reasons outlined above. If you want to go stiff poly or solid in one location, then other location should be softer poly and not left with OEM rubber.
Last edited by TostitoBandito; 05-14-2019 at 01:10 AM.
1999 M3/2/5 - Titanium Silver - Track/Weekend Toy
I have been researching it for awhile as I'm in the process of re-doing the whole rear ends. I personally think that OEM or similar duromoter for the diff bushings and slightly stiffer for sub frame (or OE) is better for street use or slightly stiffer all around (80A), which is what I'm going to do with mine. You need a little bit of shock/impact isolation somewhere especially for street use.
Last edited by Genes1s; 05-14-2019 at 03:44 PM.
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The subframe is not such a big deal since all the suspension bushings provide isolation. I think the F80 M3 rear subframe is solid mounted and some E9xM3 owners have done solid mounting with no complaints. It’s the diff that will whine if mounted too stiffly and the singing at certain rpm is obnoxious.
The ideal setup is a stiffer subframe mount, something poly most likely, and new OE diff mounts.
Either way, you'll hear some diff whine.
Last edited by Hova; 05-15-2019 at 04:04 PM.
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I went with akg 95a for the subframe and OEM for the diff. I have been very happy with the setup for my street driven E36 m3. No noticable nvh increase.
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