powerflex diff bushes -- black or purple?

[kolosy]

as part of what's turning into a complete rear end refresh, i'm swapping in poly bushes for the diff. car is track only, but i do drive it to the track (though that may change this season, we'll see i guess). is there a material difference between black and purple powerflex bushings, and any downside to going with the black ones? just more NVH? what do you guys run?

[amg6975]

Same use case and I have black diff bushings and solid subframe bushings with no rear interior and the diff is barely noticeable. I would not swap to purple if given the opportunity

[tsk94]

Track-only car? Solid.
The diff whine isn't that bad at low RPM. If you have the interior still and drive to the track it would be bearable, imo.

[kolosy]

Originally Posted by tsk94

Track-only car? Solid.
The diff whine isn't that bad at low RPM. If you have the interior still and drive to the track it would be bearable, imo.

2 hours to road america, and i'm at 3200 RPM for most of it. that's gonna be rough. the super sprint catless drone is bad enough

[tsk94]

Originally Posted by kolosy

2 hours to road america, and i'm at 3200 RPM for most of it. that's gonna be rough. the super sprint catless drone is bad enough

Fair enough. To each their own. I never found the diff whine (w/ solid bushings) to bug me on the highway at ~3500rpm in my gutted race car. The exhaust was always the loudest part.

The way I approach bushings is I want to do it only once. Which typically means going as stiff as you think you can tolerate/want the first time around. Nothing worse than a year later going through all the effort of upgrading to a stiffer bushing...

[MaximusB]

I just installed front monoball, solid aluminum subframe bushings, AKG 95A (black) diff bushings and powerflex black everywhere else. Diff whine the loudest at 110km/hr, and it does whine a bit between 50km/hr to 60ish km/hr. But nothing that bothers me and I can still have a normal conversation in the car. Personally the diff whine just becomes white noise and you probably won't even pay attention to it after a few drives.

NVH wise, the car definitely felt stiffer going over bumps and etc. But it is not jarring or bouncy. I would say it feels like I dialed up the stiffest on my coilovers by a few click. Overall, really happy with the upgrade.

[kolosy]

thanks all. ended up sticking with black. so now, i'm doing
- BW solid subframe bushings
- monoballs for the trailing arms (FCP's kit, I think they're Meyle), PO did front monoballs already
- powerflex black for the diff and spring arms
- gc rear arms

+ $500 in bolts because bolts. sigh. part of me wants to not replace the non-single-use bolts because $500 on metal, and part of me says "150k miles on a car that's now only living on track".

all that's going on top of 3DM's dedicated track kit + H&R sway bars. I think that completes this episode of "not strictly necessary but i want it" suspension upgrades for the car.

[MaximusB]

Originally Posted by kolosy

thanks all. ended up sticking with black. so now, i'm doing
- BW solid subframe bushings
- monoballs for the trailing arms (FCP's kit, I think they're Meyle), PO did front monoballs already
- powerflex black for the diff and spring arms
- gc rear arms

+ $500 in bolts because bolts. sigh. part of me wants to not replace the non-single-use bolts because $500 on metal, and part of me says "150k miles on a car that's now only living on track".

all that's going on top of 3DM's dedicated track kit + H&R sway bars. I think that completes this episode of "not strictly necessary but i want it" suspension upgrades for the car.

I was the exact same situation as you a couple months ago when I was putting together a list of all the nuts and bolts. But look at it this way, FCP/Turner/ECS all have life time replacement now. If you ever have to replace any bolts again it’ll be free.

Also how bad would you feel if you break a bolt at the track, and knowing that could be prevented if you had spent the $5 for a new bolt

[kolosy]

Originally Posted by MaximusB

I was the exact same situation as you a couple months ago when I was putting together a list of all the nuts and bolts. But look at it this way, FCP/Turner/ECS all have life time replacement now. If you ever have to replace any bolts again it’ll be free.

Also how bad would you feel if you break a bolt at the track, and knowing that could be prevented if you had spent the $5 for a new bolt

:groan: . i know, i know. but $500 on nuts and bolts?! stupid ///M tax lol.

(and i did buy all new hardware, just complaining for the sake of complaining at this point)

[Redd]

Originally Posted by kolosy

thanks all. ended up sticking with black. so now, i'm doing
- BW solid subframe bushings
- monoballs for the trailing arms (FCP's kit, I think they're Meyle), PO did front monoballs already
- powerflex black for the diff and spring arms
- gc rear arms

+ $500 in bolts because bolts. sigh. part of me wants to not replace the non-single-use bolts because $500 on metal, and part of me says "150k miles on a car that's now only living on track".

all that's going on top of 3DM's dedicated track kit + H&R sway bars. I think that completes this episode of "not strictly necessary but i want it" suspension upgrades for the car.

The only thing I'd do different is Bimmerworld rear camber arm bearing kit instead of Powerflex for the spring arms.

[MaximusB]

Originally Posted by Redd

The only thing I'd do different is Bimmerworld rear camber arm bearing kit instead of Powerflex for the spring arms.

their kit requires welding. Not something most can do at home. I reached out to BW when I was buying all the bushings and they confirmed that the Powerflex one doesn't require tack weld.