Solid Subframe Bushing, OEM Diff - NVH

[Carbonvert]

Hi Guys-

I believe I know the answer to this but am hoping to get some final reassurance before pulling the trigger.
I'm about to place the parts order for a complete rear-end rebuild and RACP reinforcement.

Current plan is to use solid subframe bushings and OEM diff bushings. Can someone with this setup give me final confirmation that you are not getting diff whine?
I have monoball RTAB's - I noticed 0 additional NVH with them - I am hoping the subframe bushings will be the same.

Lastly - Is there any benefit of using "raising" bushings like CMP for a car that is on OEM springs? The Redish plates will lower the subframe, but the CMP product description seems to indicate that they are for cars with plates AND suspension lowering - that leads me to believe they will raise the subframe too much for just plates

Thank you

[bmwfnatic]

I think I remember someone on OEM suspension here ended up needing camber arms to manage running the CMP bushings.

But the real question is, why would you want to run OEM springs while being solid bushed…

[fattycharged]

I think I remember someone on OEM suspension here ended up needing camber arms to manage running the CMP bushings.

But the real question is, why would you want to run OEM springs while being solid bushed…

Why wouldn't you? Solid subframe bushings don't add any NVH


Sent from my iPhone using Tapatalk

[Carbonvert]

I think I remember someone on OEM suspension here ended up needing camber arms to manage running the CMP bushings.

But the real question is, why would you want to run OEM springs while being solid bushed…

so it sounds like it’s too much raising then.

I run OEM springs with Bilstein B6 shocks. It’s a great setup for northeast garbage roads.

[dreamdrivedrift]

I'm running CMP subframe bushing + OE diff mounts
There is still the tiniest amount of diff whine. Noticeable only when radio off and much quieter compared to rest of road noise from tires wind etc. 1000000% better than with solid diff bushings.
I do think the rear end does "snap" more over joints and with hard shifts compared to rubber bushings
So I wouldn't say ZERO increase but I think it's very very tolerable.

[Obioban]

Solid subframe bushings add shockingly little NHV. Not zero, but about as close to zero as could be hoped for.

[Carbonvert]

Excellent. Thank you all.

Bimmerworld solid mounts it is.

[discoelk]

Why wouldn't you? Solid subframe bushings don't add any NVH


Sent from my iPhone using Tapatalk

This continues to be parroted. They definitely add NVH. Far less than the diff and tolerable for a street car but noticable with a stock exhaust.

FWIW, I am not a NVH weenie. Ran poly/poly on my zhp with a 30+ mile commute for 3+ years.

[fattycharged]

This continues to be parroted. They definitely add NVH. Far less than the diff and tolerable for a street car but noticable with a stock exhaust.

FWIW, I am not a NVH weenie. Ran poly/poly on my zhp with a 30+ mile commute for 3+ years.

Is it less than the creaking and popping sound of sheet metal?


Sent from my iPhone using Tapatalk

[bavarian3]

Also running CMP subframe bushings, stock diff bushings, mono rtabs. I overhauled all at once and didn't notice a difference before and after tbh.

[Obioban]

This continues to be parroted. They definitely add NVH. Far less than the diff and tolerable for a street car but noticable with a stock exhaust.

FWIW, I am not a NVH weenie. Ran poly/poly on my zhp with a 30+ mile commute for 3+ years.

I am a NHV weenie, and find the solid subframe bushings completely acceptable. Did you ever try running them with stock diff bushings?

[discoelk]

Yeah. It's what's in my car now. I like it a lot. It's just not stock. The same incremental change was noticed with spherical RTABs.

[Carbonvert]

Yeah. It's what's in my car now. I like it a lot. It's just not stock. The same incremental change was noticed with spherical RTABs.

If its the same incremental change as spherical RTABs then this is perfectly acceptable.

My major concern is the diff whine - The worst thing I did to this car was poly diff mounts. I quickly switched the rear mounts back to OEM and will get the front one back to OEM during this job. I was worried about reintroducing that loud whine at 70mph with the subframe mounts.

[9kracing]

CMP solid raising bushings here with OEM diff bushings.... I don't hear anything, but I have an exhaust.

If there's a diff wine, it's really really quiet. I hear nada.

[Keith_MN]

I wonder if those with diff whine have refreshed the diff fluid lately.

May be coincidence, but I noticed a very small amount of whine at highways speeds after I put in poly mounts on the subframe and diff.
A few months later I did a fluid change on the diff.
Now it is noticeably quieter with parking lot clutch noise and I'm not hearing any whine at all. I also have an exhaust, but it's not loud.