Humming from rear of car

[t-top 87]

I recently have gotten 3.73s installed. I have about 50 miles on the rear. Today while driving I heard a humming noise comming from the rear of the car. I can't tell it it is the rebuilt rear or not. I need to be driving at about 2000 RPM in fifth before I hear the noise. If I rev it to 2000 RPMs, I don't hear it. I also installed a used D/S. This replaced the 4 banger D/S shaft with the hugh balancer I had before. Is it normal to hear noises from the rear during a break in period. The gears where installed by a reputable mustang performance shop. Thanks.

 

[5.0fox]

i would say it is from the gear install they probly didnt do a very good job shimming the gears now they have a wierd contact patch. take it into the shop as soon as possible and they might be able to fix it b4 the gears wear to much

 

[ninety15.0]

if you are hearing that whining noise mostly when u let off the gas then its likely that the backlash is not set properly, which is directly related to the shims as mentioned above. Mine whined a bit when i first had them put in then after a couple hundred miles they quited down considerably to where i have to turn down the radio and shut the windows to even hear it. good luck with em

 

[t-top 87]

It makes noise whether I'm on the gas or not, but I need to be cruising at a pretty good speed before I hear it. I also need the windows to be closed. I guess I'll be calling the shop that installed them. Thanks.

 

[t-top 87]

Forgot to mention, tonight when I went for a drive and got up to speed where I hear the noise. We heard the humming and felt a vibration through the floor. Will a noisy rear vibrate through out the car?

 

[maverick0716]

When I had my gears installed they hummed while lightly on the gas staying a steady speed. I watched the guy install it and he did everything perfectly. I've since then changed out the diff fluid to put in synthetic redline fluid and the wear on the ring and pinion is perfect, they also don't hum anymore. I guess they just had to break in a little bit. These weren't Ford Racing gears by the way, they were Motive gears.

 

[t-top 87]

Thanks Guys.

 

[ECU5.0]

the gears amplify the vibration from the rear end. an aluminum driveshaft will help out a lot and the humming is from the gears being too tight like mentioned before. the shims are not right and the backlash is off. get it checked out asap before you ruin the gears

 

[t-top 87]

I've just emailed the shop where I had the gears done. I will let you know the outcome.

 

[nick26]

u-joints on that used driveshaft maybe?