Help with resonance/noise after diff switch

zanGTA · Dec 16, 2017

Hi all,

Recently I swapped my 3.15 diff for a 3.55. At the same time i put on the steeda subrfame bushing kit and red diff inserts.

At the drive noticed a strong resonance exaclty at 30mph. It was present only on slight or strong acceleration.

The shop changed the motorcraft diff oil for a bardhal and the resonance got 50% better.

Got to a road race track for some hours and coming to home the resonance get even worse and present up to 60mph. Raising the speed it becomes more acute. I searched on youtube something and I can say it is not a exactly a gear whine, but behind the reconance there is something “metallic”.

Help me!! :frusty:

pro 5.0 · Dec 16, 2017

zanGTA said:
Hi all,

Recently I swapped my 3.15 diff for a 3.55. At the same time i put on the steeda subrfame bushing kit and red diff inserts.

At the drive noticed a strong resonance exaclty at 30mph. It was present only on slight or strong acceleration.

The shop changed the motorcraft diff oil for a bardhal and the resonance got 50% better.

Got to a road race track for some hours and coming to home the resonance get even worse and present up to 60mph. Raising the speed it becomes more acute. I searched on youtube something and I can say it is not a exactly a gear whine, but behind the reconance there is something “metallic”.

Help me!! :frusty:

Is the diff you installed new or used ? Let's assume that the diff is in good working condition then what you are describing sounds like you are getting NVH from those red diff inserts, take those out and your problem will be solved. Remember anytime you put those subframe bushing kits in you are essentially solid mounting everything and it will transmit diff noise, but the diff bushings will transfer more.

zanGTA · Dec 16, 2017

The diff is the ford racing loaded with 3.55. Brand new and it has now less than 10k miles.

What sounds me strange is that an oil changes the resonance and few hours on track made it permanently worse.

I had set an appointment to get out these bushings but to do this I’ll need a full subframe realignment and I hope the driveline vibe will not come back again.

But the new noise after the track doesnt sound so much like a resonance. Ah, forgot to mention. Togheter with diff i swapped the halfshafts with the gt350 ones.

BmacIL · Dec 16, 2017

Take out the diff bushing inserts. Try BG 75W140 diff oil from [MENTION=22413]Optimum Performance[/MENTION], opmustang.com

pro 5.0 · Dec 16, 2017

Not sure what you have going on with that vibration but you changed a lot of things at once. I have all the parts in my sig and the car has no vibration or noise it drives as smooth as the day I bought it. You may want to look over your install maybe there is a visible sign of a problem like an axle nut loose, or driveshaft not tight.

zanGTA · Dec 16, 2017

BmacIL said:
Take out the diff bushing inserts. Try BG 75W140 diff oil from [MENTION=22413]Optimum Performance[/MENTION], opmustang.com

Do you recommend any additive or I can go straight with that oil? Actually the shop added something to the oil.

JohnD · Dec 16, 2017

zanGTA said:
Do you recommend any additive or I can go straight with that oil? Actually the shop added something to the oil.

They probably added friction modifier which clutch pack limited slips need. But if you bought a Torsen diff it doesn't need it. I have the BG 75W-140 oil in my Torsen and it works well.

I'm assuming you know whether you bought a Torsen diff or a regular clutch pack one?

zanGTA · Dec 16, 2017

No, it isn’t torsen.

Jeff_oddo · Dec 23, 2017

It’s the diff bushings... I have the same NVH after I installed mine.

Help with resonance/noise after diff switch

zanGTA

Well-Known Member

pro 5.0

Well-Known Member

zanGTA

Well-Known Member

BmacIL

Enginerd

pro 5.0

Well-Known Member

zanGTA

Well-Known Member

JohnD

Legend in his own mind

zanGTA

Well-Known Member

Jeff_oddo

Well-Known Member