Differential-Related Issues:
* Worn or Damaged Ring and Pinion Gears: This is a common cause of grinding noises in differentials. The gears mesh together, and wear or damage can lead to a rough, grinding sound, especially under load (acceleration or deceleration). This is often accompanied by a whine or hum as well.
* Worn or Damaged Differential Bearings: These bearings support the ring and pinion gears. Worn bearings will create a grinding or rumbling sound, potentially worsening with speed or load.
* Low Differential Fluid: Insufficient fluid lubrication leads to increased friction and grinding between the gears. Check the fluid level and condition (it should be the correct type and not excessively dark or metallic).
* Broken or Damaged Differential Case: While less likely, a cracked or damaged differential case can allow parts to move improperly and generate grinding noises. This is usually accompanied by other symptoms like leaks.
* Loose Differential Bolts: Though less common, loose bolts can allow movement within the differential, creating noise.
Axle-Related Issues:
* Worn Axle Bearings: These support the axles and their rotation. Worn bearings produce a grinding or growling noise, often increasing with speed. You might also notice play in the axle if you try to move it by hand (though this should only be done with the car securely jacked up and supported).
* Damaged Axle Spline: This is the part where the axle connects to the differential. Damage here can lead to a grinding noise as the axle slips or binds.
* Worn or Damaged CV Joints (if equipped): While less likely on a 1997 GT (depending on if it has a limited slip diff), worn CV joints (constant velocity joints) can cause clicking or grinding noises, especially during turns.
Troubleshooting Steps:
1. Check the Differential Fluid: This is the easiest and most important first step. Low or contaminated fluid is a major culprit. Inspect its color and consistency.
2. Listen Carefully: Try to pinpoint the location of the noise more precisely. Does it change with speed, acceleration, deceleration, or turns? This will help narrow down the potential causes.
3. Inspect Visually: If you're comfortable working under the car (with proper safety precautions!), inspect the differential and axles for any obvious damage, leaks, or loose bolts.
4. Jack Up the Rear End (Safely!): With the car securely supported on jack stands, try to move the axles by hand to check for excessive play. This can indicate worn bearings.
5. Professional Inspection: If you cannot identify the problem yourself, take your Mustang to a qualified mechanic specializing in rear-end repair. They have the tools and experience to diagnose and repair the issue.
Important Note: Driving with a grinding noise from your rear end is risky. Continued operation can lead to further damage and potential catastrophic failure, possibly resulting in loss of control. Get it checked out as soon as possible.
