[RRTEXGT]

Hi all,
I just bought a 2000 GT and was driving it home (about a 2 hour drive). About half way home I noticed a sound that I can can only describe as sounding like a fighter jet does when passing overhead coming from the rear of the car... not the typical whistling a bad rear end makes... it sounds like it's dry or something

I limped it home, checked the rear diff fluid and it is brand new looking and slap full. I don't have the mechanical knowledge to tear into it and inspect.

Has anyone ever experienced this? I'm pretty sure I got hosed by the seller, but wanted to get any other opinions as to what it could be.

You can get it up to speed, push in the clutch (or put in neutral) turn the car off and as long as it is moving you hear the noise... all speeds.

Thanks in advance!

[red02gt]

i know pretty little about rear ends but it sounds like youre gears are out of whack. if thats the case then swap some 3.73s or 4.10s in

[AzSonicSnake]

either its the lash adjustment, or you have a carrier bearing going out. i had this happen on my 98 gt that i owned a few years back.

[steve987fix]

Hello Noob,

It sounds like the seller heard this noise, changed the differential oil to try to fix the problem, and sold the car when that didn't work. I have a 2000 V6 Mustang that's making a similar noise from the rear. I figured out a couple ways to determine what the problem is:

1) If the sound periodically comes and goes a few times a second, drive at a constant speed and count the noises using a stopwatch. You don't have to look at the watch, just count up to 30 or 40 cycles of the noise and then stop the watch. Divide how many cycles of the noise you counted by the time to get the speed of the noise. The noise will most likely repeat at either the wheel rotation speed, or half of that. The Mustang rear wheels rotate about 13 times per second at 60 MPH, or about 9 times per second at 40 MPH, for stock tire sizes. So, it'll be easier (and safer) to count the noises at a pretty slow speed. Wheel speed (rotations / second) = vehicle speed (in MPH) / 4.6.

2) If the sound repeats at the wheel rotation speed, it can be coming from the brakes, the tires, or the ring gear in your differential. If it repeats at half the rotation speed, then it's a bearing. The bearings rotate at half of the wheel rotation speed.

3) If it's a bearing, you might be able to tell which one(s) by whether the noise goes with acceleration or not. In my case, the noise was much louder when I'm accelerating or decelerating, which indicated it was a carrier bearing. The carrier bearings are under load when you're pushing on the gas, but not much when you're coasting. If the noise is constant even when you're coasting, this indicates it's an axle bearing. These bearings are under load (the weight of the back of the car) even when you're coasting. The axle bearings are easier to replace than the carrier bearings. You do have to remove the differential cover and unclip and remove the axle shafts to replace them.

4) If the noise repeats very rapidly even at low speeds (at the wheel speed times the rear axle ratio), then it could be the pinion gear or a pinion bearing. These rotate at the engine speed, when you're in 4th gear (for a manual transmission). At normal road speeds, this would sound like a constant noise. I haven't had that problem yet.

I found a complete Mustang rear-end bearing kit for the 7.5" rear end on 50resto.com for $110. They also have one for the 8.8" rear end. I've ordered mine but haven't received it yet.

I learned these things the hard way, by replacing the wrong parts. I understand replacing the gears and the pinion / carrier bearings is tricky but I'm not afraid to get my hands greasy. I'll keep you posted on the results.

[mtucker]

i had the same noise when i got my car. it was the carrier bearing in mine.

[southernindianastang]

if your going to tear into it....take it to a pro and upgrade to 3:73's. I know you don't want to hear this but....take to someone smarter than you!!

[steve987fix]

The kit from 50resto.com had everything needed to repair this problem. Noise was coming from the left-side carrier bearing - about half of the rollers were badly scored. I put in a Traction-Lok differential along with the new bearings. This is a job I wouldn't recommend doing yourself unless you have a garage, a good set of tools, and lots of time and patience. If you've got the time and the gear, though, you can do this yourself and get really good results. I've put 1000 miles on mine since I rebuilt the rear end and it still sounds like a new car.

[97S281]

Have you checked your u joints?

[crossfire876]

Originally Posted by steve987fix Hello Noob, It sounds like the seller heard this noise, changed the differential oil to try to fix the problem, and sold the car when that didn't work. I have a 2000 V6 Mustang that's making a similar noise from the rear. I figured out a couple ways to determine what the problem is: 1) If the sound periodically comes and goes a few times a second, drive at a constant speed and count the noises using a stopwatch. You don't have to look at the watch, just count up to 30 or 40 cycles of the noise and then stop the watch. Divide how many cycles of the noise you counted by the time to get the speed of the noise. The noise will most likely repeat at either the wheel rotation speed, or half of that. The Mustang rear wheels rotate about 13 times per second at 60 MPH, or about 9 times per second at 40 MPH, for stock tire sizes. So, it'll be easier (and safer) to count the noises at a pretty slow speed. Wheel speed (rotations / second) = vehicle speed (in MPH) / 4.6. 2) If the sound repeats at the wheel rotation speed, it can be coming from the brakes, the tires, or the ring gear in your differential. If it repeats at half the rotation speed, then it's a bearing. The bearings rotate at half of the wheel rotation speed. 3) If it's a bearing, you might be able to tell which one(s) by whether the noise goes with acceleration or not. In my case, the noise was much louder when I'm accelerating or decelerating, which indicated it was a carrier bearing. The carrier bearings are under load when you're pushing on the gas, but not much when you're coasting. If the noise is constant even when you're coasting, this indicates it's an axle bearing. These bearings are under load (the weight of the back of the car) even when you're coasting. The axle bearings are easier to replace than the carrier bearings. You do have to remove the differential cover and unclip and remove the axle shafts to replace them. 4) If the noise repeats very rapidly even at low speeds (at the wheel speed times the rear axle ratio), then it could be the pinion gear or a pinion bearing. These rotate at the engine speed, when you're in 4th gear (for a manual transmission). At normal road speeds, this would sound like a constant noise. I haven't had that problem yet. I found a complete Mustang rear-end bearing kit for the 7.5" rear end on 50resto.com for $110. They also have one for the 8.8" rear end. I've ordered mine but haven't received it yet. I learned these things the hard way, by replacing the wrong parts. I understand replacing the gears and the pinion / carrier bearings is tricky but I'm not afraid to get my hands greasy. I'll keep you posted on the results.

This guy really knows his stuff. Wish you were around when I tried tackling my gear install. My nest advice is to pay to have it done right. Mine turned out to be the pinion bearing, needed to be fixed because the dude that had my cobra first really messed it up. I personally ruined a few crush sleeves and initially didnt set the backlash correctly. Took so much time and had to have a buddy come coach me through the redo.