blackmustangv6

Just like the title says, I'm hearing a whining coming from the rear of the car starting at about 45 - 50 mph getting louder as I go faster. My opinion is it's coming from the center rear, so the differential. My Mustang is an 05 V6 with a 5-spd and just over 90,000 miles. I had a t-lok and Ford 3.73 gears installed just over 3 years ago, haven't had any issues until now. Any ideas or pointing me in the right direction is appreciated, Thanks.

timmbo

Most likely the gears. Pull the cover and check the backlash with a dial indicator. Should be between .008 and .015 thousandths.

blackmustangv6

I'm hoping it's not a backlash problem. I called the shop that installed the gears and t-lok 3 years ago and they said I should start by replacing the fluids in the differential and check the wheel bearings. I believe the manual calls for 75W oil in the rear. Is there a particular brand I should get? I'm sure some will say Royal Purple, but is it worth it for my V6? And is there a particular brand of friction modifier I should use?

ODDYSEY

If your wife/girlfriend isn't sitting in the backseat, it is probably the gears

timmbo

I use Valvoline SynPower 75-140 full synthetic. Got my oil at NAPA. Grab a 4 oz bottle of Motorcraft friction modifier at the dealer.

Bearings usually make a growling noise when going out, not a high pitch whine. So chances are what your hearing is gear noise. You have to pull the rear cover to change the oil anyway so check the backlash with a good dial indicator. It's probably excessive.

blackmustangv6

I really appreciate your help timmbo. A couple of more questions though. Is it normal for the backlash to go bad after 3 years and about 45,000 miles or maybe just bad luck? And do you know where I can pick up a good dial indicator?

blackmustangv6

And oddysey, that whining comes from the passenger seat. I'm pretty sure I can't fix it either.

timmbo

It can over time yes. You can get a decent magnetic base type dial indicator either at Harbor Freight or Northern Tool.

Nuke

The whinning comes from the front end anytime I try to stick in her rear...

xylandme

My car is doing the same thing. I start to hear it around 45 and up. As far as I know, its the original rear end. Im going to try changing the fluid and add the friction mod and see what happens. Its not very loud and cant be heard with the radio on. I still dont like it though...