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Discussion Starter #1
A grinding noise has developed in my 73 Cougar XR 7. Can't tell from sound if it is the throw out bearing or differential. Running a 351c with FMX tranny and 9 inch rear end. It only grinds when I am accelerating. Clutch (throw out bearing)?
 

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A throw-out bearing shouldn't be spinning unless the clutch pedal is depressed. It is at REST the rest of the time, at least that's the way all the throw-out bearings I have used worked. Maybe you could have someone ride in the back seat and listen with their head near the floor. You need to determine whether it is engine or rear end related, and go from there.

Dale in Indy
 

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Put the rear end up on stands and at first you can put it it neutral and start rotating things by hand. Should be able to narrow it down, if not, start er up and put it in gear and then see if you can do it under no load condition....probably a rear diff bearing...? Watch the driveshaft for wobble
 

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Am I the only one that noticed he said FMX and throw out bearing, automatics do not have throw out bearings, so that is eliminated.Check rear end!
 

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Yeah, I was gonna say. If you have a FMX, I seriously doubt it would be a noisy throwout bearing.
 

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Discussion Starter #6
Hey, thanks to everyone for replying. My bad on the throw out bearing. I did put it up on jacks stands and it is coming from the rear end. Bearing going out. Timing is good, I'm ready to upgrade to an AOD and change rear end ratio to 3:50 or 3:73 from stock 2:75. Anyone with rear end ratio experiences that care to share?
 

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You don't want to say you have a lot of rearend experience --- ESPECIALLY around these guys! LOL But (only one "T") I am running an AOD with a 3.50 rear and it made it so much more drivable it's pathetic I didn't do it sooner.
 

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If you are going with a AOD, I would not go any higher than a 3.73. I am running a 3.78 and love it, at 65MPH it is tacking 2 grand, and in town it has plenty of spunk. MHO
 

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Discussion Starter #11
Thanks for the comments. I'm scheduled to put my Cat in the shop next Tuesday for the AOD and rear, I'll post what rearend ratio I decided on. I am leaning heavily toward 3:73. Can't wait to feel the difference!
 
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