Bad gear whine! With big PICS!!!

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dromeda

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Apr 17, 2004

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Sep 13, 2005

#1

• Sep 13, 2005

• #1

Alright, I have a 98 cobra convertible with stock 3.27 gears, never replaced and I have a horrbile, loud, obnoxious whine. I'm talking deafening. It goes away with the clutch disengaged, and with the clutch engaged and off the gas pedal.

So I took the diff cover off and snapped a few pics. I'm hoping someone will see something out of the ordinary.

With the first two pics I can't tell if the contact pattern is the light part on the whole tooth or the dark part on the outer part...









Please someone help!

Thanks

 

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sgarlic

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Apr 21, 2001

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Sep 13, 2005

#2

• Sep 13, 2005

• #2

Ever changed the fluid back there?

 

slo65

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May 26, 2003

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Southern California

Sep 13, 2005

#3

• Sep 13, 2005

• #3

sgarlic said:

Ever changed the fluid back there?

Click to expand...

well the cover's off.... so now he has to change it

any metal shavings in the gear oil?

 

blackink00

I missed a shift & stole Curt's money.

Mar 30, 2005

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Tempe, AZ

Sep 14, 2005

#4

• Sep 14, 2005

• #4

my 98 was the same way with my stock gears.

 

csledd

Official Ovary Punching Member

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Sep 14, 2005

#5

• Sep 14, 2005

• #5

yeah, look for those metal shavings.. that's an easy tell tell sign that you've got problems

 

tomustang

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#6

• Sep 14, 2005

• #6

bearings

 

forpit2000gt

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Jun 30, 2002

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Columbia, SC

Sep 14, 2005

#7

• Sep 14, 2005

• #7

are you sure you are not hearing a TOB. does it do it while sitting still or only at certain speeds?

 

trinity_gt

10 Year Member

Jan 31, 2003

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Sep 14, 2005

#8

• Sep 14, 2005

• #8

dromeda said:

Alright, I have a 98 cobra convertible with stock 3.27 gears, never replaced and I have a horrbile, loud, obnoxious whine. I'm talking deafening. It goes away with the clutch disengaged, and with the clutch engaged and off the gas pedal.

Click to expand...

The contact pattern looks okay (I think...what are those dark features in the first pic?). If the noise is there under acceleration/load and goes away when the load is taken away and given that the gearset is factory I'd suspect an inner pinion bearing.

 

z1n

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Aug 18, 2004

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Sep 14, 2005

#9

• Sep 14, 2005

• #9

What is that dark pattern? Is that normal?

 

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soctty7676

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Apr 4, 2005

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Sep 14, 2005

#10

• Sep 14, 2005

• #10

I have this same exact problem with my '98 GT, the noise goes away when I let off the gas or push the clutch in. But the minute I'm back on the gas, I hear what sounds like a scraping sound or something from the rear end. BTW - I just had a brand new clutch kit installed, so that is out of the question.

I am going to try and change the fluid this weekend and see if that helps. Heck for all I know it might be dry as a bone in there, I bought it used and have not checked the fluid.

 

D

dromeda

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Apr 17, 2004

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Sep 14, 2005

#11

• Sep 14, 2005

• #11

I just changed the fluid (only 55,000 miles) and added friction modifier and that had 0 effect on it.

I didn't see any metal shavings when I drained it.

I am not sure that it isn't a TOB. It does however, sound like it is coming from the back. Most of the interior is out of the car which would obviously contribute to the whine, but not this bad.

trinity_gt said:

The contact pattern looks okay (I think...what are those dark features in the first pic?). If the noise is there under acceleration/load and goes away when the load is taken away and given that the gearset is factory I'd suspect an inner pinion bearing.

Click to expand...

That is opposite of what I'm hearing. With a lot of load it gets quieter. With 0 load it goes away completely. With little load it whines like a mother. It is at it's worst when I am driving a constant speed, say 60, giving it just enough gas to stay there, REALLY loud.

Doesn't matter which gear I'm in. Shift from 5th to 4th, same amount of whine, change 4th to 5th, same.

z1n said:

What is that dark pattern? Is that normal?

Click to expand...

I don't know what that is, but the pinion looks to have a similar mark where it contacts the ring at that spot too.

Thanks for all the suggestions!

 

1fast4by

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Sep 14, 2005

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Nashville, Franklin, Murfreesboro. All over really

Sep 14, 2005

#12

• Sep 14, 2005

• #12

How many miles?

The pattern on the outside of the ring gear tooth doesnt look right either, I can see where it is matching on the pinion. Is there a taper on the gear where the pattern is? It looks like it has been improperly set up, and if so may have caused some gear wear as well as bearing wear

 

D

dromeda

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Sep 14, 2005

#13

• Sep 14, 2005

• #13

1fast4by said:

How many miles?

The pattern on the outside of the ring gear tooth doesnt look right either, I can see where it is matching on the pinion. Is there a taper on the gear where the pattern is? It looks like it has been improperly set up, and if so may have caused some gear wear as well as bearing wear

Click to expand...

55,000 I just changed the fluid and took these pics this weekend.

 

1fast4by

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Sep 14, 2005

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Nashville, Franklin, Murfreesboro. All over really

Sep 14, 2005

#14

• Sep 14, 2005

• #14

Id say you probably have a bearing problem. But it looks like the rear is set up incorrectly. If your not gonna do it yourself, id suggest Putting the covor back on filling it up and putting it in the shop befor the gears get destroyed to...but then again that would be a good excuse for some nice motorsport 3.73s

 

D

dromeda

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#15

• Sep 14, 2005

• #15

A buddy of mine, who knows a thing or two about cars, said that the wear pattern looks a little deep and may cause the whine.

Also, everytime I shift out of gear, there's a clunk, along with everytime I shift into gear. Would that be incorrect backlash?

 

trinity_gt

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Sep 15, 2005

#16

• Sep 15, 2005

• #16

1fast4by said:

Id say you probably have a bearing problem. But it looks like the rear is set up incorrectly.

Click to expand...

Yeah, I take back what I said earlier about the contact pattern now that I've looked at the pics with a half decent monitor. It appears that the pattern is biased too far toward the heel of the ring gear teeth. Perhaps a tad more pinion depth is needed... Anyway, if they're truly factory, they've been like that for a good 7 years now. If the noise is a recent development and it's from the rear it'd certainly most likely be bearings. After 7 years, I wouldn't suggest changing the setup on gears...I'd just replace them with FRPP 4.10s (you've got a Cobra after all...)

While in there, have them check those pinion bearings

 

forpit2000gt

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Sep 15, 2005

#17

• Sep 15, 2005

• #17

1st off, the black part isn't important, from the pictures ,I would say it is fine. You should see the shiny part in the middle which is the contact patch, it should be middle to inner. I still don't think that is causing the problem. I believe now that it is a pinion bearing. Get some 4.10s or 4.30s, inner and outer pinion bearings, install new gears and be happy. You have to pull the carrier to replace the pinion bearing anyway. At least 4.10s......