8 3/4 Rear Axle Noise Question

Rusty34

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Hello Everyone,

With a rekindled interest I just purchased a restored 71 Charger after being away from the hobby a long time. Good to be back. The car was very nicely rotisserie restored by Restore a Muscle Car in Lincoln, NE. The only problem I have with it right now is a loud singing ring and pinion noise on the coast side which will need to be fixed. The car is now in a good friend's shop and we have it up on a lift with both axles out. The differential is mounted in a vise to check backlash and run a gear pattern test to look at the pinion depth setting. The case is a 489, gears are 3.23 and it has Sure-Grip. Everything about the rear axle assembly including brakes and wheels, is brand new. It looks like they might have purchased the entire rear axle assembly from one of the vendors.

My first question is: The axles are both aftermarket (Moser?) and we noticed right away that there was no axle end-play adjuster on the RS. Perhaps they have engineered a ball bearing set-up to replace the OEM tapered roller bearings and adjuster? It's been a long time since I've worked on these cars and availability of parts seems different now and improved 1000%.

Also, we noticed a lot of metallic particles in the gear oil we drained out which was also new. This car has about 60 miles on it since restoration. Is it possible this is just normal wear particles coming from the new Sure-Grip?

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Cranky

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Whine on coast down usually means the pinion is too deep. Generally, noise on accel means it's not deep enough. Your SG unit looks to be an aftermarket unit and having metal particles usually isn't a good sign for just having 60 miles on it. Also will need to see a more close up pic to see if you have ball bearings (Green Bearings) on the axles. Ball bearing place the axles so you don't need an adjuster. How much back lash does it have?
 

pnora

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Looks like an O-ring on the bearing which would mean aftermarket green/ball bearing style. Noise is not good. Clean it and get a pattern on both drive and coast sides. Load the ring gear in both directions. That should tell you the story. Can you change it and make the noise go away is a big IF. Most of the time when gears are run in its almost impossible to correct them noise wise.
 

Cranky

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Looks like an O-ring on the bearing which would mean aftermarket green/ball bearing style. Noise is not good. Clean it and get a pattern on both drive and coast sides. Load the ring gear in both directions. That should tell you the story. Can you change it and make the noise go away is a big IF. Most of the time when gears are run in its almost impossible to correct them noise wise.
You must have a much better screen resolution than I do if you can see an o-ring there lol
 

Rusty34

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So far all we have done is check ring gear run out and backlash. Backlash was checked in 4 places and was .002 to .006. We have not done the pattern test yet as we will have to get some white lead. There was only retainer plates on both sides with no adjuster and with only a quick visual check of the bearings we noticed snap rings in place where an oem setup does not have them. I didn't take a close look at them when we pulled the axles but I do think they might have been ball bearing type. I also noticed the aftermarket retainer plates looked to be bent as if something might have been forced upon tightening the nuts on each side l'm away from the car right now doing some research on this trying to learn more about how it is supposed to be. From what I see while looking through Year One and Classic Industry catalogs. I'm starting to think the restorer purchased an entire 8 3/4 axle assembly from a vendor. I would have to confirm that to be sure but everything in it is new. The car is about a mile up the road from me but when I go back over I will take a closer look at the axles and get more pictures.
 

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.006 is what I use for a minimum and .002 is way too tight. And I hope a vendor wouldn't let a rear end go out of the door with bent retaining plates but bent ones is pretty common from people who do not know what they are doing.
 

R/T Boy 67

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If there is a thrust block in the diff, then you need to remove it. That should clear up your axle issues. I think a complete tear down and inspection is necessary to cure your backlash, noise and shrapnel issues.
 

Rusty34

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@Cranky, thanks for your reply. We were surprised too when we saw that .002 pop up at one of the check points. What to do about that?

@R/T Boy 67:
There IS a thrust block in there! Wow! That explains why the wheels were so difficult to rotate in neutral up in the air. I wonder if the metal particles came from the bound up ball bearings? We have some serious decision making to do now. If it was a purchased complete 8 3/4 axle assembly those run $4250!
 

pnora

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You must have a much better screen resolution than I do if you can see an o-ring there lol
It is blurred as I expand it but I do see a dark line. Must be the snap ring as the poster said he noticed.
 

RemCharger

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Reset it at .006 at the tightest point. Could try loosening one cap bolt opposite ring gear and tighten adjuster.
Metal not from wheel bearings, they aren't in the oil.
Thrust block removal should be done, not sure how on that style carrier.
@Cranky, thanks for your reply. We were surprised too when we saw that .002 pop up at one of the check points. What to do about that?

@R/T Boy 67:
There IS a thrust block in there! Wow! That explains why the wheels were so difficult to rotate in neutral up in the air. I wonder if the metal particles came from the bound up ball bearings? We have some serious decision making to do now. If it was a purchased complete 8 3/4 axle assembly those run $4250!
 

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@Cranky, thanks for your reply. We were surprised too when we saw that .002 pop up at one of the check points. What to do about that?
Well, you could try like what's been mentioned and reset the pinion depth (after checking to confirm where it is now) then set the backlash at the proper setting at the closest point. You might get lucky and it'll be ok or maybe it'll make less noise on coast. I would like to see what the gear pattern looks like now though....but kinda hard to see that unless your phone takes really good pics.
 

Rusty34

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Yes, I'll try to get a gear pattern check once the white lead arrives. Can you tell if these are Chrysler or Richmond gears by the numbers showing on the ring gear in the picture above?

OK on the bearings not receiving oil so metal likely not from them. I will carefully inspect them to see if re-usable. They will have to be removed anyway to replace the bent retainer plates. Another thing we found, there was no thin metal shim gasket behind the brake backing plates and no white foam gaskets in front under the retainer plates. I am attempting to make a list of parts I need to order. Should I pull it apart and disassemble the sure grip for a look inside? I guess everything really needs to be cleaned up now?
 

RemCharger

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Look like factory gears. If I were to guess, it was all original and they plopped in the auburn? differential.
 

R/T Boy 67

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I would replace the bearings. To remove the thrust block you have to remove the spider gear pin, which means removing the ring gear. Not a bad idea anyway as there could be a burr or a piece of crap between the gear and the carrier, causing the backlash variation. You could shorten the axles instead of removing the block, but it is not the way I would go in this case. ( pun intended)
 

Rusty34

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Many thanks guys for all the helpful suggestions! I don't want to short-cut this one so I will disassemble it to remove the thrust block. It needs to be cleaned anyway and being all apart will permit a more thorough cleaning.
 

Cranky

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Yes, I'll try to get a gear pattern check once the white lead arrives. Can you tell if these are Chrysler or Richmond gears by the numbers showing on the ring gear in the picture above?

OK on the bearings not receiving oil so metal likely not from them. I will carefully inspect them to see if re-usable. They will have to be removed anyway to replace the bent retainer plates. Another thing we found, there was no thin metal shim gasket behind the brake backing plates and no white foam gaskets in front under the retainer plates. I am attempting to make a list of parts I need to order. Should I pull it apart and disassemble the sure grip for a look inside? I guess everything really needs to be cleaned up now?
Been awhile since having a set of Richmond gears at my place but iirc, they had the name on the edge ring or at least their logo. The ratio will usually be 10-41 for a 4.10 but the factory gears will have a part number along with the ratio typed out as 4.10 and will usually have a date code too. Also, an after market gear will have the pinion depth etched into the face of the pinion head and will be something like a + number or a - number and the factory gears won't be marked. Btw, Green Bearings (ball bearings) are packed with grease and sealed by the manufacturer.
 

Rusty34

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I seem to recall seeing red grease around the sides of the wheel bearings. I'll get pictures to help ID what they are and I will check the pinion head for a + or - number when I go back over.
 

khryslerkid

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You don't need to remove the "block" when using Green Bearings. Just the Buttons. They look like these. They are held into the block with a rivet type pin. A lot of them are already loose from the pin being broke like in the picture. Look and see if they are still in there.
20170729_094529.jpg
 

Rusty34

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Ahh, thank you for that khryslerkid! I will look in there again.
 
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