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Three new differential gear sets, two mechanics shops, 5 set ups and I still have noise.

Yeah, kind of hate to give up my DynoMax mufflers but may have to go to some glass packs like I had in the 60s and 70s.
Both mine have gear noise.
one is 741 case 8-3/4 with unknown manufacturer 3.91s
other one is Dana 3.54 OEM gear set

BOTH howl,,,,, although slightly different speeds and conditions.

I've decided to live with it
I had a friend, since passed, who owned a rearend shop. He told me that if initial setup isn't right, and gears howl, they will ALWAYS howl from then on, no matter what is done to setup. Only solution is new gears.
Cass told me that once. I tried readjusting them, but he was right....
Just wanted to chime in, my brand new Strange S60 with spool and 4.56 gears has a whine on decel that sounds like an ambulance coming up behind me. Kinda reminds me of my moms Rambler wagon when I was a kid.
Can’t hear it with open headers though.
I have a new Strange 60 with 3.54's and it is perfect. Have another Strange 60 with 3.23's and it has a whine from 2100-2400 rpm. Been that way from new and hasn't changed a bit. It's just a crap shoot with all these gears nowadays imo.
My deceased friend set up my 3.91 8 3/4, and also two different sets of used gears for my nine inch (his specialty), 5.14s and 4.57s. All of them are quiet, but I don't remember the gear brands.
Pretty sure I couldn't get that done today, even with new gears.
Well, I took the shop owner for a ride and he said it was definitely gear noise. It does make a bit of noise on coast down too - just not as loud as the Richmond’s. He and his mechanic said they were factory lapped gears and set up real easily - both are standing by that the position the pattern looked as good as you can get. They replaced one pinion bearing and I asked if maybe the other was bad. They said all the other bearings were fine. They mentioned all the same things about gear harmonics, sad state of aftermarket gears, etc. He said they are seeing it in new vehicles too and 40 to 50 seems to be a common speed for noise. He checked on the gears he normally uses (Revolution) but they stopped carrying 8-3/4 gears several years ago. He said a used, OEM gear set might be my best bet. I wish now I had kept the old 3.23 set.

He said they would be glad to take another look at the pattern if I wanted to pull it again just to double check it. He said they might be able to play with the pattern a little to get it better but it’s just trial and error and might get worse and might take several attempts with no promise of success. I told him that after pulling and replacing it 4 times already I might as well do it again and we can just look at it and we can then decide then whether to mess with it. He seemed willing to help.

After that he recommended some noise insulation under the seat and at the trunk divider. He didn’t mention louder pipes though.:rolleyes:

I think you'll find the consensus is once installed and ran you'll never get them quite by readjusting.

Doug had a good point about the housing being out of square can cause this but your previous/original set was quite.

It takes a good eye and many rears, setting them up to get a good pattern. I've seen videos where a guy will set one up without any tools except an impact gun and swear they're done right. And he might get by with doing it his way. I've learned in the past how to do it right and still had to consult with an expert because it wasn't working out the way I wanted. I had to settle for the best pattern on the last rear I did and it wasn't perfect by any means. I still say it's what we're dealing with now days with all of these overseas manufacturers. I don't care if it's a TV, refrigerator, or car parts.
I’ve only put a few easy miles (maybe 15) with 90-140 oil in it so I doubt I’ve set much of a pattern - probably no more than the factory lapping. I have the car on stands on my lift, tires off, everything loose, axles out, driveshaft out, differential unbolted and draining in an hour. Jack it down tomorrow. Practice makes for speed. I told him ill bring it down and we’ll look at the pattern and decide then whether to try anything further on it or just go with insulation.
Maybe its the gear oil...Have you tried some good 80 w 90, non synthetic? Just a thought.
Are you speaking of the pinion bearings?
yes preload on the pinion. I don't have the spec for you but the preload is different depending on wether or not you are reusing the old bearings or installing new bearings. There may be information from the gear company you used or it may be in a Mopar service manual for your year vehicle. To give you an idea the preload for used bearings is probably around 10 inch/lbs and for new bearings maybe 18 inch/lbs but look it up because that's just a guess to give you an idea
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Both shops I’ve used recommended 90/140. Seems a little heavier than necessary - tough to even roll the car on a cold morning but that’s what they recommended. I believe it is synthetic.

edit: No it isn’t synthetic. It’s Lucas Dino formula.

I bought a crush sleeve eliminator kit that they used and they set the Pinion torque for used bearings although they did replace one of them due to some superficial damage.
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I looked all over for straight 140 gear oil and had to buy it on line.
My Tru-Trac helical gear limited slip was noisy from the begining at slow speed turns.
Tru-Trac said not to use synthetic or limited slip additive gear oil..Straight 140 did the trick.
I know we are talking about ring and pinion noise. I just wanted to pass that along.
Here is my brand new Power-lok for a D60 sitting in a lathe, the gear side flange is out of spec and corrected. The gears can not set up properly if the carrier is out of spec.
With todays lousy quality kontroll you must measure all parts..... Even parts from well known suppliers included.

Pulled the differential again and started new thread on tooth pattern - difficult to tell much however.