Diff Fluid
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
Diff Fluid
Got a whine coming from the rear end. Nothing bad, just barely noticable.
Going to change the rear end fluid this weekend.
Just curious as to how often everyone changes theirs. I'd bet that mine's original.
Going to change the rear end fluid this weekend.
Just curious as to how often everyone changes theirs. I'd bet that mine's original.
Racer
Joined: Jun 2005
Posts: 293
Likes: 1
From: Pace Florida
I'm starting to get a whine too. Let us know if that helps.
Thread Starter
Drifting
Joined: May 2007
Posts: 1,491
Likes: 2
From: North Royaton Ohio
I'm sure hoping that it fixes it. That's the one area of the car that I've neglected to address, so I'm sure it needs something. I really don't feeling like shelling out almost a grand for a new diff or to get mine rebuilt. We'll see what happens.
Race Director
Joined: Jun 2005
Posts: 10,189
Likes: 206
2018 Corvette of Year Finalist
2017 C3 of Year
Same here, had some noise coming from the rear. It's amazing what a little fluid can do. Try to remove all of the old fluid, I used a small hand pump. After filling the diff. take the car to an open parking lot and do several figure 8's at slow speed, this will bring the fluid up into the gears. Also don't forget to add the whale oil, or the newer synthetic additive! Good luck 
WB
WB
Advanced
Joined: Apr 2008
Posts: 59
Likes: 0
From: Drummonds TN
Don't forget special flui
I just chanced my diff fluid and it made a world of difference in the sound of the rear end. my 78 calls for a 4 OZ tube of special fluid that goes in the diff with the change. look at the specs and see if yours requires this. DON"T forget it as I think this is what makes the big difference. Then just fill with 80-90 diff fluid. I have no drain fluid and had to suction mine out...worked well.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
You may not have as much fluid in there as you expect....if it hasn't been changed/topped-off in 35 years. There is NO drain plug..only a fill plug. You have to syphon or suction out as much of the old fluid as you can (turkey baster with a length of hose, etc.). Then refill with GM differential gear lube and some posi-trac fluid. Put in half of the gear lube, then the posi-lube...then fill rest with gear lube until it starts to run out of the fill hole. Plug it up and go.
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Pro
Joined: Oct 2004
Posts: 624
Likes: 24
From: Shoreline WA
7T1vette: you make it sound simple. Archive search has one member using "Lucas 85-140 gear oil & GM posi additive." Would you recommend something else?
I agree with you that a change or topping off might be in order. Is it a short one-hour garage session plus a short test drive? Something I should probably do before summer.
I agree with you that a change or topping off might be in order. Is it a short one-hour garage session plus a short test drive? Something I should probably do before summer.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Once you have the new lube, posi additive and a way to suction out the old stuff, the job is a "piece of cake". You do need a square drive adapter for your ratchet to remove the plug; I think it's a 1/4" or 3/8" square recess in the plug. You can put some thread sealer on the plug when you reinstall, if you want; but don't overtorque it or you can crack the housing.
Race Director
Joined: Apr 2003
Posts: 19,352
Likes: 654
From: Tampa, Florida
Once you have the new lube, posi additive and a way to suction out the old stuff, the job is a "piece of cake". You do need a square drive adapter for your ratchet to remove the plug; I think it's a 1/4" or 3/8" square recess in the plug. You can put some thread sealer on the plug when you reinstall, if you want; but don't overtorque it or you can crack the housing.
Easy job. I used a big crescent wrench to get the plug out.
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
I've got a whine as well, but when I let off the gas it goes away, give it gas it's back. I also notice it seems to go away when cornering at speed. Don't have any clunking sounds. Think it's also just a fluid change I need?
Melting Slicks
Joined: Nov 2001
Posts: 2,668
Likes: 43
From: Eastern US XX
Nope! Probably a bearing or incorrect lash. How long has it been doing it?
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
If a bearing is the problem, one of the side bearings I would assume?
Le Mans Master
Joined: Sep 2002
Posts: 6,689
Likes: 0
From: Michigan
St. Jude Donor '15
I put Schaeffer's 267 Gear Lube in to quiet my diff. It helped.
http://www.schaefferoil.com/gear_oils/267.html
http://www.schaefferoil.com/gear_oils/267.html