Howling noise when under acceleration at 45mph+
 

As the title says, I fitted a number of parts to the car and now when I press the accelerator when above 45 there is a howl from the rear. Also the car now has more road noise and is stiff and crash over bumps.

The parts I installed included:
steeda upper control arm mount (UCA set to factory position.)
Steeda upper control arm(length matched to factory)
Steeda/energy suspension polyurethane bushings in diff housing
rear steeda swaybar and endlinks
Whiteline LCA and relocation brackets
Steeda adjustable front sway bar
diff fluid change with 2.5 quarts of fluid and friction modifer.

Any ideas what the problem could be?

NVH, You removed all the soft rubber parts so now you are hearing resonance.
I also don't know if the pinion angle changed when you put the Relocation brackets and different LCA on.

Did you grease the poly bushings before you installed them? The poly bushings MUST be coated will silicon grease before they are installed or they will be very noisy. As far as the howl in the rear diff goes you may have changed the pinion angle when you installed the Whiteline LCA and relocation brackets so they must be adjusted to bring you pinion angle back to spec. The brackets lowered the mounting point for your LCA so setting it the same as your stock piece may incorrect, it must be adjusted to to get the pinion angle back to spec.

Yes I used the supplied grease on all the contact points of the bushings. I'm not an expert by any means, I didn't think the LCA and the relocation brackets change the pinion angle, I thought it was just the UCA that did that. What shops/garages and bring the pinion angle back to factory spec. Would a Ford dealer do it?

I did a lot of similar mods, I did notice an increase in NVH but nothing like a howl. Do you have 3:73 rear gears? They have more whine than my 3:31 gears, maybe that is what is going on? I'm just guessing here...

Yes I have 3.73 gears but it didn't howl before.

I would be thinking about the same things as already suggested:

1) Was the noise always there, and you are just hearing it now? The harder bushings will transmit more NVH but I wouldn't expect this to be extreme.

2) Did the pinion angle change? It sounds like there were enough changes in the rear that it could have easily changed. I think this is worth checking, ASAP before the gears develop a bad wear pattern . . . and I think the only way to do it is with a gage; very difficult to do without a lift so probably worth a visit to a local shop that is familiar with this.

That's the nasty 3.73's making their presence known. It's possible you just never noticed before, but now because of the new parts you are more keen to any noises your stang is making. My rear-end makes the same howling noise and I haven't taken it in to the dealership, but I'm wondering if I should. :dunno: