8 3/4 Rear End Noise
#2209286
12/07/16 01:06 PM
12/07/16 01:06 PM
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Joined: Jan 2004
Posts: 755 Tempe, AZ
loco340cuda
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 755
Tempe, AZ
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Now that I have gotten my Cuda back on the road (after being restored) and have put a few hundred miles on it I am now noticing a noise coming from the rear end.
The noise only happens when I make a right hand turn and it seems to happen only when the car seems to be swaying to the drivers side. It does not make the noise when I make a left hand turn and it does not always make the noise when I turn right (only sometimes).
The noise sounds like it is coming either from the 3rd member or the drivers side axel near the driver side rear wheel, hard to tell. The noise sounds like a clunking sound that seems to repeat while making the right hand turn but once the car straightens out it goes away. Again it only does it every so often.
Some background on the rear end. It is an 8 3/4 with 3.91 gears, sure grip. I had a rebuilt 3rd member (3rd member by Dr. Diff) put in the car 8 years ago and never had any issues or noise. This year the rear end was dis-assembled, cleaned, and painted as part of the restoration. The only things changed to it where the old original style bearings where replaced because the where worn and all the gaskets and seals were replaced. The other thing to note is that the bearings were replaced with a set of Dr. Diff green bearings.
I'm not sure what is causing this noise but I suspect either something was not re-assembed correctly or something is now out of adjustment. I'm kinda bummed because I suspect whatever it is the rearend will have to come apart to address this and after a full year of restoring this car I am flat out sick of working on it. Nevertheless it is what it is and I need to suck it up and get it fixed.
I know some of you folks here on the board know what this issue is so I need some advise on what to do to trouble shoot and fix this.
-Thanks
70 Cuda 340 4 speed - now stroked to 416ci (SOLD) 2017 Mustang Shelby GT350
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Re: 8 3/4 Rear End Noise
[Re: loco340cuda]
#2209314
12/07/16 01:50 PM
12/07/16 01:50 PM
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Joined: Jun 2005
Posts: 5,102 Western Md.
skicker
"The Champ"
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"The Champ"
Joined: Jun 2005
Posts: 5,102
Western Md.
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There is a very (very) small amount of play in and out with the green bearings on my Satellite. Check for wear marks and make sure there's no contact between the drum and backing plate. Only other thing I can think of is does it have a posi additive in it???
...FAFO...
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Re: 8 3/4 Rear End Noise
[Re: loco340cuda]
#2209331
12/07/16 02:25 PM
12/07/16 02:25 PM
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Joined: Apr 2003
Posts: 348 Texas Hill Country
Centerline
enthusiast
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enthusiast
Joined: Apr 2003
Posts: 348
Texas Hill Country
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Agree. When the diff was reassembled and the gear lube replaced, did you use the special limited slip additive? If not this could easily cause the noise.
Last edited by Centerline; 12/07/16 02:27 PM.
Centerline 64 Dodge Polara 426 Street Wedge - For when I want to go fast 99 Corvette Z-06 - For when I want to turn corners
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Re: 8 3/4 Rear End Noise
[Re: Centerline]
#2209349
12/07/16 02:52 PM
12/07/16 02:52 PM
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Joined: Jan 2004
Posts: 755 Tempe, AZ
loco340cuda
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 755
Tempe, AZ
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Thanks for the feedback guys.
I embarrassed to say i did not know I needed to use any kind of limited slip additive. I just added gear oil to the rear end.
Is their a particular kind/brand of limited slip additive that I need?
70 Cuda 340 4 speed - now stroked to 416ci (SOLD) 2017 Mustang Shelby GT350
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Re: 8 3/4 Rear End Noise
[Re: loco340cuda]
#2209442
12/07/16 05:41 PM
12/07/16 05:41 PM
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Joined: Jan 2003
Posts: 75,004 U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,004
U.S.S.A.
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If it is only happening on 1 side I would check the axle bearing on that side. If the rear was run after it was built and the only change since then were greenies then I think it's pretty easy to figure out what is making he noise. The bearing might have been damaged when it was being installed ?
What kind of sure grip does it have ?
running up my post count some more .
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Re: 8 3/4 Rear End Noise
[Re: JohnRR]
#2209448
12/07/16 05:53 PM
12/07/16 05:53 PM
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Joined: Jan 2004
Posts: 755 Tempe, AZ
loco340cuda
OP
super stock
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OP
super stock
Joined: Jan 2004
Posts: 755
Tempe, AZ
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It is a 489 case with 3.91 gears that I purchased from Dr. Diff. Unfortunately I don't know what type of sure grip it is.
Also, do I need to drain the gear oil out of the 3rd member and then put in the friction additive and then put new gear oil back in?
70 Cuda 340 4 speed - now stroked to 416ci (SOLD) 2017 Mustang Shelby GT350
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Re: 8 3/4 Rear End Noise
[Re: loco340cuda]
#2209483
12/07/16 06:42 PM
12/07/16 06:42 PM
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Joined: Dec 2004
Posts: 2,368 Wheatfield, NY
Cuda340
top fuel
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top fuel
Joined: Dec 2004
Posts: 2,368
Wheatfield, NY
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Another question; did you put the axle seals in the rear end tubes?
You do not have to remove the 3rd member. You only need to remove about 5-6 ounces of gear oil. You can do that a few different ways.
Last edited by Cuda340; 12/07/16 06:54 PM.
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Re: 8 3/4 Rear End Noise
[Re: ben-dart]
#2209741
12/08/16 12:16 AM
12/08/16 12:16 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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is it neccessary to drain out several ounces? I wouldn't think several more would cause an issue (foaming)
live every 24 hour block of time like it's your last day on earth
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Re: 8 3/4 Rear End Noise
[Re: RapidRobert]
#2209745
12/08/16 12:21 AM
12/08/16 12:21 AM
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Joined: Nov 2007
Posts: 21,822 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
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is it neccessary to drain out several ounces? I wouldn't think several more would cause an issue (foaming) No, it's not. As long as the additive will fit. In the case of the Ford additve, we're only talking 4 ounces.
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Re: 8 3/4 Rear End Noise
[Re: loco340cuda]
#2210873
12/09/16 08:39 PM
12/09/16 08:39 PM
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Joined: Jan 2003
Posts: 20,176 Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,176
Park Forest, IL
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Did they take the center spacer out of the diff when they switched to green bearings?
"Everybody funny, now you funny too."
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