Strange Rear End Noise

[Swarzkopf]

Never heard a noise like this on a car....

When I first fire up the Mustang, there is a fast, loud rattle from the rear end for a few seconds, which then goes away. Revving the motor doesn't create this noise again.

Then, during my first turn while driving, the noise comes back, just as intensely as before. As the car warms up, it usually goes away, but might come back later during another turn.

If the car is warm, it doesn't make the noise at startup.

The sound can best be described as a very fastly repeating, hollow sounding rattle. If you put a golf ball in a big empty plastic water jug and shook it real fast, you'd get this noise. It sounds similar to a blown strut, but faster.

I have no idea what it is. My differential seems fine, the rear shocks are A-okay, the exhaust system is as secure as it will ever be, and I don't think it's the U-joint because they usually sound differently when they're going.

Any suggestions?

 

[wytstang]

Man that's weird it really sound like your pipes are hitting the body but you say it's secure. Do you have any thing in the trunk that might cause this noise?

 

[Joes95GT]

Do both tires spin when the posi locks up?

Is the sound coming from the "pumpkin" section or from somewhere in the rear suspension area?

Joe

 

[Swarzkopf]

wytstang: My first thought was I had something in the trunk...cleared the trunk out and it's still happening.

The exhaust system is very secure.

Do both tires spin when the posi locks up?

Yes, though the car is starting to fishtail more when I get on it while straight. The rear kicks left pretty good now.

Is the sound coming from the "pumpkin" section or from somewhere in the rear suspension area?

It's hard to really pin it down...it sounds more like it's coming from the passenger side rear suspension area, but I can't say for sure.


Thanks for the feedback and fast responses.

 

[Joes95GT]

Yes, though the car is starting to fishtail more when I get on it while straight. The rear kicks left pretty good now.

When you say kick left, that may not necessarily be a good thing. Do you mean the car likes to take off in one direction? Does the car make the noise while sitting still or is it while it's in motion? Did the car ever start making the noise before the ring and pinion was installed? How long ago was it installed?

I may be getting somewhere...

Joe

 

[wytstang]

Open up the the "pumkin" and take a look inside check out everything ring&pinion spider gears good luck.

 

[Swarzkopf]

The 4.10 ring and pinion was installed back in August....the problems just coming up now.

Does the car make the noise while sitting still or is it while it's in motion?

Both- it makes the noise right at startup, then stops. It then makes the noise again while turning during driving.

When I say "kick left", I meant that if I jump on it from a stop, the rear of the car tends to swing to the right, causing the front of the car to point left. I couldn't remember which way it fishtails when I first posted. :lol

 

[Joes95GT]

Both- it makes the noise right at startup, then stops. It then makes the noise again while turning during driving.

OK. It's not your suspension. Is the car in gear when the noise occurs? I'm not guaranteeing you anything, but I can bet you something is wrong in the rear. Pull the diff cover and check all the obvious stuff. Check the ring and pinion gears for chipping or not being "straight". Check the posi and make sure the spider gears aren't thrashed. Check out the shims on each side and make sure nothing looks goofy. Check the torque on the main caps if you have access to a torque wrench. That's all I can think of for now...

Joe

 

[94TURBO5 O]

You've got a busted rear dude. Do you pop your clutch and drive aggressively?

I had the same symptoms and it was there for months and I pulled the rear and sure enough I had a broken tooth on my pinion and one piece was just clunking around in there. Pull the cover like Joe said and take a look inside.

 

[95snoozer]

my rear is trashed and grinds on slow turns.
My spider gears are fuxord.

I now have a horrible vibration above 80. I mean HORRIble. this has gradually gotten worse as the rear has been driven on its last leg.... about 15K miles hehe. I figured it was a misbalance in the diff but i am wondering if the ujoints might be bad too.

BTW i have a new rear to put in but am waiting for the 4.10s to come out of my friends car so i can do it both at once. I have been waiting forever but his car has been down with no motor.