awbreyjd

I just installed the complete Ford Racing SVT Rear Axle Assembly as we broke the axle tubes in my stock one. It came with the 3.73's. Unit comes assembled and full of oil already. After about 200 miles of driving and multiple warm up/cool down cycles I noticed it developed a pretty loud whine between 70-80mph. The first day I drove it 30 miles on 2 seperage occasions over a highway at 75mph and there was no whine. the second day I cruised a little before lunch then mid day decided to make the 30 mile trip again and at 75 when under acceleration or maintaining throttle it whines. under Decel it is much quieter.

tigercrazy718

could maybe be the type of gears ford is putting in their svt rears. some forms of the OEM gears whine, while others dont (can't remember which company's gears whine, been a while since i researched gears).

awbreyjd

yea thats what I am gathering in my research as well. that and having solid upr control arms not is making the resonance even louder than it would be otherwise.

PNYXPRESS

Did you check the fluid levels or just take Fords word that it was filled?

awbreyjd

We checked. How do you think we new it was filled. We thought for sure it was shipped dry but nope full.

PNYXPRESS

How about after it started making noise? what was the fluid level like? My rear axle was pushing fluid out due to high speeds and hard cornering and it started whining like a little girl. Extended the breater tube, refilled it and the whine went away.

Derf00

Check the expected pinion angle with the new rear and see if it's what ford recomends for the GT500 or Boss. I know they ride a little lower than a stock GT so that spec may be different than what you run stock. That's usually a common cause for differential whine.

moosestang

Did it come with the axle tubes welded?

IME, the higher you go numerical, the more noise it's going to make. If you have rod ends on your upper control arm, then you are going to hear even the slightest whine.

I bet I could go test drive a brand new 5.0 with 3.73's and it would have some whine at 70, but probably hard to hear with the stock drive shaft and stock bushings dampening every noise.

awbreyjd

It was welded. Fluid is still full but am going to change it out for some Royal Purple syn. and yes I knew I would hear it louder with the solid mounts I just kinda wanted to see if they are common to whining. The stock rear with 331's or 4.56's didnt whine at all.

VistaBlueFrank68

It's also probably been sitting in storage for a longtime, do you think that might effect the fluids? Of all my gear jobs the only one that ever whined was a 3.73 done by a person who I suspect eye-balled a job that takes 1/1000 of an inch precision, and it whined! My factory 3.73 with Torson is quiet at 70+. It's possible the factory worries more about quality control with a built unit going to a dealer who'll complain then a unit that's going to sit till ordered.