Ringing Sound? Any help?!

Hey everyone, so I just swapped out my rear end and drive shaft and put the stock rear gears and a brand new drive shaft. (71RR 727 Auto, 7290). The car runs great put when I hit around 75 mph, I hear this faint then strong ringing sound. Nearly identical to the sound a finger makes when traced around a rim of a glass. When I lift the gas, it stops. I can't figure out where the noise is coming from. I'm thinking the rear. Any help would be appreciated.

Used gears? Tough to set back up to the original pattern they were before... Very well could be that.

Did you set up a new chunk or just swap it out?

Check the pinion seal shield. If it has one it can get bent easily and rub the housing which will cause the drive shaft to amplify a ringing sound.

I'm thinking classic ring/pinion issue.

I think it might be the ring/pinion.

Is this something that is serious in nature if left not cared for?

Its sounds dumb now, but I literally swapped out the drag end that was on the car and put the stock one that I had in a crate back on the car.

It sounds like you just swapped the center section, am I correct? Do you remember if the rear end made any noise when it was in the car before? I'm only asking because if you're like me, memory has a way of forgetting things! Is there any noise at all at lower speeds or is it only at freeway speed?

So the car had low end Richmond gears. All I did was swap out that rear for the stock gear. The drag gears never made a noise when it was in the car before. I put in a brand new 7290 axel yoke kit and a brand new drive shaft that went right into the transmission. Everything installed perfectly. Around 30-40 mph you start to hear a whine that disappears around 70mph. That's when the ringing sound happens. It will go away and come again every 30 seconds or so. Once I back off the gas a bit, it goes away.

If you swapped the pinion yoke did you retorque it and check the back lash.

No I didn't

You didn't swap pinions or you didn't check it?

You are NOT providing enough info. Nobody knows what you actually did to the car.

Did you take apart the center section? Meaning did you separate the ring gear FROM the pinion gear?

What rearend is it? 8 3/4? Dana 60? something else. Did you change the WHOLE thing? brake drum to brake drum? Or remove ONLY the ring gear and pinion gear, and reinstall the stock 2 gears? Sounds like you removed the RING GEAR and PINION GEAR and didn't re-set the backlash, and didn't re-torque the pinion nut.

8 3/4 rear end. I changed the whole thing. Brake drum to brake drum.

Did you do anything with/to the pinion gear nut on the rearend that you put it? Anything to the ring gear? Did you take out the pig at all?

It's like trying to pull teeth with some people, they want help but won't give out any useful info.

I'm sorry, I'm not an expert with rear ends. No need to be like that. I sincerely appreciate the help from everybody here.

No, I didn't touch the anything in the stock rear end. Didn't touch the ring gear. I literally bought a new 7290 axle yoke kit from Year One and a drive shaft and took the original rear end that came with the car when I bought it, the stock gears and assembled. I probably sound like an idiot, but I'm just trying to learn.

That's how you learn, by doing it, and asking about it. So you installed the yoke kit, but didn't torque the pinion nut when you installed it. How tight did you get the pinion nut? Very tight, VERY tight, or sorta tight?

And that axle yoke kit, is that a yoke and u-joint, or just the two sized u-joint?

Thanks for your patience and information. I tightened the pinion nut very tight. The drive shaft I ordered came with greased ujoints. They fit perfectly in the axle yoke kit. Like I said, everything I installed fit perfectly. No resistance.

Now we're getting somewhere...do NOT drive the car. As Tom is asking above, we need to know your method of torque on that yoke/pinion nut. Unless you match marked the nut's position relative to the pinion shaft I am afraid you are looking at more education. We also need to know what rear it is..489? 742? 741?

I believe it is a 742, but am not 100% sure. I've driven it twice now with no issue, but am I looking at a catastrophic failure in the near future with those noises? I initially used an air wrench and then tightened it with a wrench

Well, a 742 is MUCH more forgiving given your scenario than a 489... But it still takes a LOT of torque..240lbs if I recall correctly. Not easy to do, but the difference between an undertorqued 742 and a 489 is massive in terms of potential howl/whine. Meaning I don't think your torque on the pinion nut is the issue.

If it's truly a 742 or 741

Chances are the air wrench tightened it to about 50 foot pounds, depending on the air wrench of course, and how big it is. The proper torque is about 200 to 250 if I remember correctly, but I'd have to look it up, been a few years.

Gotchya. How do you differentiate between the 489, 742 and 741. Casting numbers?

Yup, the last 3 digits of the numbers on the side of the case.

A 741 or 742 you can torque.A 489 with the crush collar and a new yoke would be tough to get back to the same spec it was.The noise while coasting,but gone when accelerating I'm thinking pinion bearing.It may be frome the yoke torque being off, but the bearings could also have rust or pitting from sitting a length of time dry.
RT

Stop using the word literally, you don't know what it means.

Well, I just looked and its a 489! (2881489) Now I'm worried from what you said.

Everyone else on here is being helpful with information. I'm trying to learn from the car vets on here. You are absolutely no help being the grammar police or making rude comments.

Thanks to RTSrunner, Pacnorthcuda and amxautox. You guys have been incredibly helpful. Thanks for your patience.

Well, being a 489 means you have a "crush sleeve" on the pinion that determines bearing preload on the pinion. You certainly did not replicate this on the yoke replacement. That's not easy to do even if you know what you are doing.

Do not drive it. Your looking at a pig removal, pinion removal, new sleeve or spacer upgrade and reassembly. A fair amount of work.

I suppose as a last ditch, you could try checking for pinion slop (for/aft) and torquing till that's gone, but that's a pretty shade tree approach!

Thank you so much for your input, advice and information. I sincerely appreciate the time and patience.

Or buy a kit and replace the crush sleeve with a solid sleeve and thin spacers, but that is a lot of work also. Measuring, taking it back apart, putting in another spacer and assembling, and measuring, and doing it again, and again until you get the back lash proper. It's one of those things I'd probably have a shop do. I guess they still have those solid spacer kits for that pumpkin/pig.

or simply call Dr. Diff, bite the bullet, and get one of his ready to bolt in nodular pigs and be done with it.DO NOT SHOP AROUND OR CALL ANYONE ELSE. you will be so much happier!

THANKS GUYS!

I remember the first time I did a rear gear assembly. Reset the ring and pinion on my '67 Mustang after blowing the spider gears. I had to take it all apart in the winter in Illinois. Got it back together and talk about HOWLING!!!

Broke the side gears again, and did a better job the second time.

LITERALLY LITERALLY LITERALLY LITERALLY LITERALLY LITERALLY LITERALLY LITERALLY LITERALLY ......Ooooohhhh......I can't stop.....LITERALLY.....Aargh