Diff chatter/grinding
Thread Starter
Instructor
Joined: Nov 2020
Posts: 140
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From: Colorado Springs
Diff chatter/grinding
Searched a bunch of threads but not exactly my problem. For background—I was having an odd noise at cruise/turns that sounded like it was coming from the diff. At first i thought the diff was self destructing but then for no reason stopped on its own. A year ago i had changed diff fluid 75/90 and 1 bottle AC delco additive. Was perfect for the year until just recently. Jacked the car up and added a second bottle of additive. Now i still have the noise at low or high speed when cold whether driving straight or turning. As things warm it seems to subside. Definitely a metal on metal chatter/grind that reminded me of a deteriorating harmonic balancer hitting the timing cover but never happens when stopped.
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2025 C3 of the Year Finalist - Modified
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At any rate, yes we can all sit here and guess.
But it sounds like it's a good time to remove that diff from the car and go through it.
But it sounds like it's a good time to remove that diff from the car and go through it.
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From: Connecticut, USA
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Advanced
Joined: Oct 2024
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From: Michigan
At one time GM recommended replacing diff fluid including the special additive. Then find an area big enough to perform figure eights to clean the posi plates that were slicking while driving especially when turning. No specific number of figure eights, just perform until noise diminishes..
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Thread Starter
Instructor
Joined: Nov 2020
Posts: 140
Likes: 27
From: Colorado Springs
Pulled the diff and found a chip on the ring gear. Still searching for origin of the grind/chatter. So now what is the community’s experience with replacements for a 3.08 ratio? Yukon? Richmond? Other?
Tech Contributor
Joined: Aug 1999
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From: Connecticut, USA
There are no more USA made gears left today. Almost all - if not all, today are Chinese. Corvette gears are specific, meaning they are made only for the corvette, and as a result there are less offerings today. Some gear companies like Motive only offer 355 or 370 vette gears. Others offer the full range only today they charge by the ratio, whereas the USA made gears were sold at one price regardless of ratio. Price gouging in my opinion. Some gears have names that sound similar to now closed companies, but they are not USA made and in fact were reboxed gears that failed first run inspection. Price shoppers end up unknowingly with them thinking they found a deal.
Thread Starter
Instructor
Joined: Nov 2020
Posts: 140
Likes: 27
From: Colorado Springs
69L88—Not looking to change ratios. The case claimed it was 3.08 but the guts turned out to 3.37 or so. My diff guy has it now so I cannot comment on the chip severity or location
Thread Starter
Instructor
Joined: Nov 2020
Posts: 140
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From: Colorado Springs
Update—found a good used 3.08 gear set (thanks Howard) for my diff guy. He found a shattered clutch plate and 2 clips just floating around inside. All back together now and waiting for time to install.