Put in 8 3/4 and now I have a howl...

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LivewireBlanco

LivewireBlanco

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I got an 8 3/4, 741 case, 3.23 open rear from a 68 GTS. I put plenty of grease in the bearings and set the preload after cleaning it out. It looks to have sat for a long time. The teeth on the gears looked really good but that's the only inspection I could do.

When I I'm driving it above 40 I can hear it howl a bit. The only time it didn't is when im keeping my speed steady. It makes noise on acceleration and when I let off the gas.

Does this sound like the axel bearings, pinion bearing, gears...? I have new green bearings but I haven't installed them yet. How could I test to figure it out and if it's the gears could I just live with it? I have no idea how long it's been like this or if it's cause it sat a while. I even changed the fluid from 80-90 to 85-140 and it stayed the same.
 
Does the pitch change accelerating vs decelerating
 
Pinion gear depth is incorrect. Whether it can be corrected depends on how long it was run that way. If it's already set up a wear pattern being run incorrectly, forget it. It's done.
 
RustyRatRod said:
Pinion gear depth is incorrect. Whether it can be corrected depends on how long it was run that way. If it's already set up a wear pattern being run incorrectly, forget it. It's done.
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I have no clue since I just got it and it came from a car that sat for many years. Should I just run it as is?
 
LivewireBlanco said:
I have no clue since I just got it and it came from a car that sat for many years. Should I just run it as is?
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What "I" would do is drop the drive shaft out and check the pinion nut torque. They are notorious for backing off. If you find it loose, if it's not destroyed the seal (or anything else) yet, you can retighten it and stake the pinion shaft end to the nut to keep it from backing off again.
 
take it out and check everything again with marking compound. 741 is easier to adjust than a 489 as it has shims instead of a one and done crush sleeve. Could just be Rob's loose nut.
 
I have a similar howl between 41 and 45 mph, decel or accel. Had the chunk out 2x to reset everything, still howls. Strange gears.
 
LivewireBlanco said:
I got an 8 3/4, 741 case, 3.23 open rear from a 68 GTS. I put plenty of grease in the bearings and set the preload after cleaning it out. It looks to have sat for a long time. The teeth on the gears looked really good but that's the only inspection I could do.

When I I'm driving it above 40 I can hear it howl a bit. The only time it didn't is when im keeping my speed steady. It makes noise on acceleration and when I let off the gas.

Does this sound like the axel bearings, pinion bearing, gears...? I have new green bearings but I haven't installed them yet. How could I test to figure it out and if it's the gears could I just live with it? I have no idea how long it's been like this or if it's cause it sat a while. I even changed the fluid from 80-90 to 85-140 and it stayed the same.
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please explain what you ment by ''setting the preload''
 
Years ago when I worked for car dealers in the 80’s.
When we heard a whine or noise the car manager would give us a banana peel to ad to the diff. It would grind it up and the fibers would quiet the noise for sometimes years.... lol! I know not the proper way to fix BUT your post brought back a memory from the past. Lol!
Honestly it is hard for us to determine what noise you have just by a single post. gears could had some rust or bearing are bad. So many issues to work around. The only way to properly diagnose and fix is take it apart and figure it out.
Syleng1
 
Syleng1 said:
Years ago when I worked for car dealers in the 80’s.
When we heard a whine or noise the car manager would give us a banana peel to ad to the diff. It would grind it up and the fibers would quiet the noise for sometimes years.... lol! I know not the proper way to fix BUT your post brought back a memory from the past. Lol!
Honestly it is hard for us to determine what noise you have just by a single post. gears could had some rust or bearing are bad. So many issues to work around. The only way to properly diagnose and fix is take it apart and figure it out.
Syleng1
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Any way to listen for it and rule out the axle bearings for sure? Put it on Jack stands and listen to where it comes from?
 
Syleng1 said:
Years ago when I worked for car dealers in the 80’s.
When we heard a whine or noise the car manager would give us a banana peel to ad to the diff. It would grind it up and the fibers would quiet the noise for sometimes years.... lol! I know not the proper way to fix BUT your post brought back a memory from the past. Lol!
Honestly it is hard for us to determine what noise you have just by a single post. gears could had some rust or bearing are bad. So many issues to work around. The only way to properly diagnose and fix is take it apart and figure it out.
Syleng1
Click to expand...
Yep, you just brought up a old memory for me. They used to throw saw dust. It would quiet it down, but eventually ruin the pig.lol.:realcrazy:
 
LivewireBlanco said:
The axle adjuster was set to .008" of play.
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Gears whine, bearings roar.
A mismatch of the pinion to ring gear is what causes whine.
Could be a loose pinion like RRR says, or it could be a pinion depth issue.

The best way to find out is to use the pinion depth tool to get it right.
THEN set the backlash.
The tool tells you exactly where the pinion should be, and that number is usually stamped into the end of the pinion gear.
 
Im going to assume this rear has been set up wrong from the factory and lived its life like this. Im going to attempt what rusty said and tighten the hell out of it and see what happens. When guessing everyone is agreeing it's not the axle bearings.

I put it on Jack stands and got the car up to 40 and it was quiet. Im guessing cause no load.
 
LivewireBlanco said:
Im going to assume this rear has been set up wrong from the factory and lived its life like this. Im going to attempt what rusty said and tighten the hell out of it and see what happens. When guessing everyone is agreeing it's not the axle bearings.

I put it on Jack stands and got the car up to 40 and it was quiet. Im guessing cause no load.
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Not saying it never happened but I never saw one from the factory howl. Don't go crazy tightening that nut or you may strip the threads. It's supposed to be torqued to 150 ft. lbs if I remember right
 
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