True.
thoughts on differential drain plug
Thread Starter
Le Mans Master
Joined: Oct 2010
Posts: 6,921
Likes: 838
From: melbourne florida
2023 C3 of the Year Finalist - Modified
thoughts on differential drain plug
i know some have done it and i think it may be a good way to get more garbage out . any suggestions on how or why not?
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Yes. I had the bottom of the diff drilled and tapped 1/4'' NPT for a drain plug many years ago, with no problems. My car is a street driven small block. I needed to put a bit larger hole in the strut bracket to access the plug. I just had the shop make the hole dead center while the diff was apart, but I've seen a paper pattern with drill bits and a tap for sale recently (at Corvette Central, look at 582267) that offsets it a bit.
Instructor
Joined: Jul 2011
Posts: 138
Likes: 0
From: Hayward SD
I have read several threads where its recommended to change gear lube and add the posi additive.
So, what gives??? lube change or no change?
Race Director
Joined: Apr 1999
Posts: 11,520
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From: CORVETTE 77 385 C.I. TEXAS
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I use 85W-140 Valvoline syn power. I can't say that I swear by it because you would have to do back to back testing under the same conditions with a Dino gear oil. I do know that my 20 year old 4.11 richmond ring and pinion were still looking brand new. My custom hardened yokes looked brand new. My Tom's Stage 8 posi unit was so physically warn out that it went in the garbage. It was only 4-5 years old. I rebuilt my rear end with 3.55 gears and drilled for a drain plug.
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Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
I might have abused mine a little though.
Drifting
Joined: Aug 2005
Posts: 1,372
Likes: 4
From: Springfield VA
Yea the only reason I would do that is if I was racing or the diff was known to have issues. I have never heard of any factory issues with the Diffs in C3's. That and even the basic dino stuff was good for 100k in most let alone the Syn options out there now.
Now my Nissan Titan diff has a drain plug but titan trucks are known to have bad diffs. So in that case a drain was a good thing.
Now my Nissan Titan diff has a drain plug but titan trucks are known to have bad diffs. So in that case a drain was a good thing.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
I for one don't agree with this statement. The problem is with the soft metal stock Yokes. I bought my 79 Vette new and in less than $50K miles on the OD the yokes ends had worn down past the snap rings. It filled the gear oil full of metal flake and destroyed the rear end. Our Rear ends are a POS right from the factory built with substandard parts.
I might have abused mine a little though.
I might have abused mine a little though.
With George. These have metal disc clutch packs and the side yokes wear on the center pin. They are full of metal shavings if they have never been serviced and these shavings are death to the roller bearings in there. I would recommend a fluid change at least every 30,000 miles or 5 years. Pretty cheap to change the fluid and yes, it really is a PITA to draw the fluid out through the fill hole. I would worry about drilling and tapping the case with a high HP application though.
Burning Brakes
Joined: Aug 2008
Posts: 878
Likes: 55
From: Deep South Denmark
I for one don't agree with this statement. The problem is with the soft metal stock Yokes. I bought my 79 Vette new and in less than $50K miles on the OD the yokes ends had worn down past the snap rings. It filled the gear oil full of metal flake and destroyed the rear end. Our Rear ends are a POS right from the factory built with substandard parts.
I might have abused mine a little though.
I might have abused mine a little though.
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
If you decide to install a drain, it is not very difficult. If you have any miles on it, the bottom of the case will have plenty of crud on it. I'd recommend pulling the cover and cleaning well before adding fresh lube and doing this.
Back a few years, GTR1999 posted a differential rebuild procedure in which he described installing a drain. I followed suit and placed this one. Don't go all the way with the NPT tap, ideally, you want the collar to be flush on the inside. This will allow most of the lubricant to drain when you remove the plug. Locate the hole where there will not be interference from any brackets.
[IMG]
[/IMG]
Back a few years, GTR1999 posted a differential rebuild procedure in which he described installing a drain. I followed suit and placed this one. Don't go all the way with the NPT tap, ideally, you want the collar to be flush on the inside. This will allow most of the lubricant to drain when you remove the plug. Locate the hole where there will not be interference from any brackets.
[IMG]
[/IMG]
Melting Slicks
Joined: Apr 2008
Posts: 2,621
Likes: 242
From: Russell Ontario
St. Jude Donor '09
WOW "red" you need to take that car out and get a little dust on it! It's so clean
I cleaned my diff only cause I took it out ,it was leacking fron the side yoks, but the inside was nice and clean 65k on it .Ron
I cleaned my diff only cause I took it out ,it was leacking fron the side yoks, but the inside was nice and clean 65k on it .Ron
Racer
Joined: Feb 2009
Posts: 495
Likes: 5
From: Lexington KY
While I had the diff out I drained, repainted, put a new gasket, and put new fluid in. While I was there I decided to put the drain plug in as well. No longer need to remove the cover to change fluid...
Instructor
Joined: Oct 2011
Posts: 153
Likes: 0
From: Des moines Iowa
79 L82 rear end gear oil fill hole
I wanted to make sure my 79L82 has enough gear oil in the rear end
can anyone please tell me where the fill hole is? I looked and didnt see
a place to pour some in. thanks
can anyone please tell me where the fill hole is? I looked and didnt see
a place to pour some in. thanks
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
If you are going to drain and refill, and you have a limited slip diff, don't forget the posi additive. They were all posi, starting in maybe 72.
If all you are doing is topping it off, not important. Just start out with the diff cold. Hot diff fluid expands, and if the used fluid spills, and gets on your clothing, the only thing that will remove the oil stain is scissors!
If all you are doing is topping it off, not important. Just start out with the diff cold. Hot diff fluid expands, and if the used fluid spills, and gets on your clothing, the only thing that will remove the oil stain is scissors!
Last edited by gcusmano74; Dec 22, 2011 at 05:26 PM.