Adding some compliance & softness back in

[Burkey]

Gibbo, it's the diff inserts. I found the exact same thing when I fitted mine (red Steeda) Start there for sure! Cheers.

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[jbailer]

I haven't heard someone having problems with NVH using the red Steeda diff inserts unless they were also using the CB005. Maybe it's an either or thing. I'm using the red inserts and the Steeda subframe braces also and no NVH at all.

Regarding the harshness, I agree with the dampers. The Steeda adjustable Pro-Action offer a nice adjustment range that others have had a lot of success with. I know this one is going to sound dumb and real easy to dismiss but trust me worth looking into. What did you do with your bumpstops when you lowered it? I lowered mine when the S550 was new, at that time I was told no need to trim the bumpstops. The rear of mine was harsh. Talking with Steeda, they told me to trim my bumpstops. When I took them out, they were really tore up. After trimming, it was much better but still it would bang on bigger bumps. Then Steeda came out with their adjustable bumpstops. I put those in the rear and it made it even better. That combined with a little more fine tuning of my dampers is what was needed to make the rear more compliant.

 

[Norm Peterson]

Hi there


Clearly getting soft in my old age, current car is 2015 UK GT PP M6 with following suspension work:-
- FRPP dampers

Car handles and grips insanely well but for street use as a daily it's almost too sharp and the rear seems overly harsh.

FRPP dampers do have some reputation for harshness, I think at the rear in particular.

If it was me, I'd try a set of adjustable shocks & struts dialed down near full soft. Without changing the springs, at least at first.


Norm

 

[xXANCHORMONXx]

It's the diff and trans stuff, remove it and I guarantee you'll be happy.

 

[armykyle1 [HACKED ACCOUNT]

The diff inserts gave me the gear whine and some clunkiness. There's definitely some design flaws in ford's IRS on these cars. I'm gonna change fluid and see if that helps the whine. I have a few other ideas to try still.

 

[jabrax]

FRPP dampers do have some reputation for harshness, I think at the rear in particular.

If it was me, I'd try a set of adjustable shocks & struts dialed down near full soft. Without changing the springs, at least at first.


Norm

Im on frpp and steeda progressives at the moment, and yes it is a little rough on imperfect streets and roads.

About to order adjustable proactions, just need to make a decision on staying with progressives and trying out the combo or just switching to a linear spring. For me the the rear is more harsh.

 

[xXANCHORMONXx]

The diff inserts gave me the gear whine and some clunkiness. There's definitely some design flaws in ford's IRS on these cars. I'm gonna change fluid and see if that helps the whine. I have a few other ideas to try still.

Not a design flaw

I've put poly in Evos, m3s, audis, camaros and subarus, gear whine is what you get when you put poly in.

 

[jbailer]

Not a design flaw

I've put poly in Evos, m3s, audis, camaros and subarus, gear whine is what you get when you put poly in.

I have the Steeda red differential bushings and absolutely no gear whine at all.

 

[xXANCHORMONXx]

I have the Steeda red differential bushings and absolutely no gear whine at all.

Do you still have the oem cradle bushings?

 

[jbailer]

Do you still have the oem cradle bushings?

Yes, I keep all of my OEM parts so I can put them back when selling the car.

 

[MtnBiker]

One thing you might want to try is expanding foam insulation inside the rear subframe around where the sub-frame bolts to the chassis (essentially anything tubular shaped). Kelly at BMR turned me onto this. Used a product called "Great Stuff" for home insulation. I have the Delrin subframe bushings...can be a bit harsh. Always concerned about placebo effect but yes the NVH is noticeably reduced. Might be worth a try.

 

[Rebellion]

One thing you might want to try is expanding foam insulation inside the rear subframe around where the sub-frame bolts to the chassis (essentially anything tubular shaped). Kelly at BMR turned me onto this. Used a product called "Great Stuff" for home insulation. I have the Delrin subframe bushings...can be a bit harsh. Always concerned about placebo effect but yes the NVH is noticeably reduced. Might be worth a try.

I assume this helps on the noise part of NVH...do you have a pic on where to apply the foam?

 

[Rebellion]

Im on frpp and steeda progressives at the moment, and yes it is a little rough on imperfect streets and roads.

About to order adjustable proactions, just need to make a decision on staying with progressives and trying out the combo or just switching to a linear spring. For me the the rear is more harsh.

Why not try to swap back to PP shocks?

I'm guessing you need less damping, these FRPP are quite stiff, IMO. I'm using the BMR handling rears with the FRPP shocks...Steeda progressives should be way softer, I think it needs softer dampers. I'd suggest trying PP shocks before you spend lots on the proaction adjustables (I suspect you'll have to put them in full soft or half turn at most).

 

[xXANCHORMONXx]

Yes, I keep all of my OEM parts so I can put them back when selling the car.

That's why you are ok.

I've done both combos.

Poly diff mounts stock cradle as well as delrin cradle and stock diff.

Once I went delrin cradle with poly diff I had enough.

 

[GTPP]

Could be the 20" wheels with (I assume) lower profile tires than stock. I'm running FRPP track pack, CB005, steeda RLCA bearing, and PP 19" wheels w/stock size tires. The tire place recently put 255/40 - 19s on the rear by mistake and the ride immediately went to shit. The lower profile tires transmitted every road imperfection into the cabin. Once the correct size tires were put back on the car, the ride is silky smooth again.

Probably an unpopular suggestion, but going back to 19s could help the ride and preserve the handling by allowing you to keep all your other mods.

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