Strange noise

[jscott]

On my way home yesterday, after driving the car for 2+ hours I started to hear a noise. It sounded like if you were driving past a saw mill, a high speed metal noise that would come and go. When I would take my foot off the gas it would stop immediately, Revving the engine in neutral (fmx auto) revealed it was not coming from the engine. To me (poor hearing) it sounded like it was coming from the rear, but it was not constant, would start then after a few seconds fade (thus the driving past a saw mill thought) It would happen mostly at 44mph-60mph but also heard it lower once or twice. I have been waiting to get her into the shop for a diffy seal replacement (slow drip leak) as well as an output shaft seal replacement (slow tranny fluid drip). If not the engine what could it be that would stop when not in gear?? Thanks for your thoughts.

 

[Sheriff41]

Check your u-joints.

 

[Tnfastbk]

sounds to me like a bearing trying to seize up somewhere. I know an alternator will do that only when it is charging at time. But could be many things. Let the hunt begin. Keep us posted. Just check the simple things first.

 

[jscott]

My first thought was a bearing but why would it stop as soon as I take my foot off of the gas?

 

[Tnfastbk]

like previously mentioned, check your u joints and could be something in the rear axle/pinion which would unload whenever you let off the gas. Not in gear would also remove the load from the rear axle, be it the pinion, u joints or whatever the case may be.

 

[Sheriff41]

My first thought was a bearing but why would it stop as soon as I take my foot off of the gas?

When you take your foot off the gas, you are changing the load on the drivetrain.

 

[Don C]

One of the main causes of a differential seal leak is a problem in the differential, usually the pinion bearing going out or loose.

 

[Hemikiller]

Grease your u-joints, If it still makes the same noise, then you'll need to look at the differential. You might have a pinion bearing on the way out. Those bearings see a tremendous amount of load, which changes on throttle position.

 

[rcadd1ct]

Check fluid level in the rear end, too

 

[69 Rustang]

When you take your foot off the gas, you are changing the load on the drivetrain.

Agreed, it could be something in the engine, but without load it may not manifest the symptoms.

 

[basstrix]

As has been implied or stated, it sounds like a pinion bearing. Get that checked ASAP as it will destroy the ring & pinion if it hasn't damaged already (assuming that's what it is).

 

[jscott]

I was finally able to get under the car today, I wanted to check the fluid level in the differential. I guess the only way to do that is the racket size plug in the driver side, correct? I pulled it and fluid started to run out so I put the plug back in. Would that say I have enough fluid in the diffy then?

 

[Sheriff41]

Sounds like you diff is filled.

 

[rcadd1ct]

I was finally able to get under the car today, I wanted to check the fluid level in the differential. I guess the only way to do that is the racket size plug in the driver side, correct? I pulled it and fluid started to run out so I put the plug back in. Would that say I have enough fluid in the diffy then?

Check it with the car in level ground. Axles not drooping.

I drive up on ramps in the front then jack the back up and set the tires on a second set of ramps

Yes the fill plug is also the check hole.

 

[jscott]

Check it with the car in level ground. Axles not drooping.

well I don't have ramps. If I put the front on jackstands then use a floor jacks to jack up each rear tire to normal hight would that work the same? After the axle is on jack stands of course.