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Grinding/knocking from diff under deceleration
#1221284
04/23/12 06:00 PM
04/23/12 06:00 PM
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Joined: Jan 2003
Posts: 3,719
Space Station #5
471Magnum
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I suspect the pinion depth is messed up on my 8.75 rear, but I figured I’ll solicit some opinions as I get ready to pull it.
Road Runner has a ‘489 case 3.55 sure grip in it. It makes an occasional knocking noise while coasting/ decelerating. It doesn’t always do it, but it’s quite frequent, and it definitely emanates from the rear. It also has a vehicle speed dependent harmonic vibration.
I figure if it were a bearing issue that I’d have issues under acceleration or cruise as well.
It's done this pretty much from the day I got the car two years ago. I’ve had so many other issues with which to contend that I’ve just let it go up to this point.
Now I’ll be swapping out the center section for my trusty set of 2.76’s later this week in preparation for the Power Tour, so any visually obvious issue will be revealed. I half-expect to find chunks of pinion teeth in the housing.
Needless to say, before those 3.55s go back in, I want to get them straightened out.
-Jim
I can fix it... my old man is a television repairman.
He's got the ultimate set of tools... I can fix it.
Currently Mopar-less
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Re: Grinding/knocking from diff under deceleration
[Re: Pacnorthcuda]
#1221287
04/23/12 06:15 PM
04/23/12 06:15 PM
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Joined: Sep 2011
Posts: 369
California, USA!!!
WheelsUp73
enthusiast
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enthusiast
Joined: Sep 2011
Posts: 369
California, USA!!!
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Quote:
Your 489's crush sleeve may have lost its preload, allowing pinion slop.
Exactly. Any way you look at it it needs to be taken apart and inspected.
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Re: Grinding/knocking from diff under deceleration
[Re: 268RTs4ME]
#1221289
04/23/12 06:49 PM
04/23/12 06:49 PM
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Joined: Jan 2004
Posts: 27,347
Today? Who Knows?
1_WILD_RT
Management Trainee
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Management Trainee
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Posts: 27,347
Today? Who Knows?
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When you accelerate the pinion is trying to push out the front of the housing & the load is carried by the large inner pinion bearing.... When you decelerate the pinion is being sucked into the ring gear... The small bearing is trying to keep it in position.... If the preload backs off the pinion rides to deep & can actually chew on the carrier.... When you pull it apart you'll likely see gear marks on the carrier....
"The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."
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Re: Grinding/knocking from diff under deceleration
[Re: 1_WILD_RT]
#1221290
04/23/12 08:07 PM
04/23/12 08:07 PM
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Joined: Jan 2003
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Space Station #5
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I'll pulling it tomorrow night, so we'll know soon enough.
-Jim
I can fix it... my old man is a television repairman.
He's got the ultimate set of tools... I can fix it.
Currently Mopar-less
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Re: Grinding/knocking from diff under deceleration
[Re: 268RTs4ME]
#1221291
04/23/12 08:23 PM
04/23/12 08:23 PM
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Joined: Jan 2003
Posts: 75,066
U.S.S.A.
JohnRR
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Quote:
Possibly the shaft that slides through your spider gears is sliding out every now and then and hitting your pinion,had that happen to me one time, no noise until i decelerated, check it out, the little bolt could have snapped that holds the shaft in.
Just an FYI , the spider gear shaft is heald in place by a short dowel pin in the cone type sure grip ... assuming that is what this one has.
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Re: Grinding/knocking from diff under deceleration
[Re: JohnRR]
#1221292
04/23/12 08:44 PM
04/23/12 08:44 PM
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Joined: Jan 2003
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No idea what SG is in there, but it's working and locks pretty aggressively. Hopefully what ever it is still useable or re-buildable.
-Jim
I can fix it... my old man is a television repairman.
He's got the ultimate set of tools... I can fix it.
Currently Mopar-less
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Re: Grinding/knocking from diff under deceleration
[Re: 268RTs4ME]
#1221293
04/23/12 09:05 PM
04/23/12 09:05 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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Grand Haven, MI
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Quote:
Possibly the shaft that slides through your spider gears is sliding out every now and then and hitting your pinion,had that happen to me one time, no noise until i decelerated, check it out, the little bolt could have snapped that holds the shaft in.
that happened to me on my old 489 case...the spider cross shaft walked out on me
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Re: Grinding/knocking from diff under deceleration
[Re: patrick]
#1221294
04/23/12 09:07 PM
04/23/12 09:07 PM
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Joined: Jan 2003
Posts: 75,066
U.S.S.A.
JohnRR
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I Win
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Quote:
Quote:
Possibly the shaft that slides through your spider gears is sliding out every now and then and hitting your pinion,had that happen to me one time, no noise until i decelerated, check it out, the little bolt could have snapped that holds the shaft in.
that happened to me on my old 489 case...the spider cross shaft walked out on me
I had a cone with a broken dowel once, but what kept it from walking out was the fact that the spider gear WELDED itself to the shaft 
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Re: Grinding/knocking from diff under deceleration
[Re: 268RTs4ME]
#1221298
04/24/12 02:44 PM
04/24/12 02:44 PM
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Joined: Jan 2003
Posts: 75,066
U.S.S.A.
JohnRR
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I Win
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Quote:
Thats just what I said. The shaft is probably sliding out. Because dow pin or bolt is broke.
I was just letting you know that it's a DOWEL PIN , the factory Borg Warner cone type in an 8.75 does not have a death bolt .
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Re: Grinding/knocking from diff under deceleration
[Re: 471Magnum]
#1221300
04/25/12 10:44 PM
04/25/12 10:44 PM
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Joined: Jan 2003
Posts: 3,719
Space Station #5
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Got the 3.55s out tonight. No obvious carnage, but I'm not done inspecting them.
-Jim
I can fix it... my old man is a television repairman.
He's got the ultimate set of tools... I can fix it.
Currently Mopar-less
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Re: Grinding/knocking from diff under deceleration
[Re: 471Magnum]
#1221301
04/26/12 10:28 AM
04/26/12 10:28 AM
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Joined: Jan 2003
Posts: 75,066
U.S.S.A.
JohnRR
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I Win
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Quote:
Got the 3.55s out tonight. No obvious carnage, but I'm not done inspecting them.
Cone or clutch type suregrip ?
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Re: Grinding/knocking from diff under deceleration
[Re: 471Magnum]
#1221303
04/26/12 11:11 AM
04/26/12 11:11 AM
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Joined: Jan 2003
Posts: 75,066
U.S.S.A.
JohnRR
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Quote:
Cone.
If you can't see anything visual you will probably have to disassemble it to see if something is broken inside , same would hold true for a clutch type.
How did the oil look ?
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