drain plug ?
Instructor
Joined: Jul 2006
Posts: 112
Likes: 0
From: vt
you're not missing anything. there is no drain plug. you either have to take the diff cover off, or use a pump to suck the oil out. i recommend pumping it out, as it is much easier than taking the cover off.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
There's another way. Tap a hole in the bottom of the assembly and install the proper sized plug (bolt). This will make future drains a breeze. See below:
http://i137.photobucket.com/albums/q.../VetteRear.jpg
http://i137.photobucket.com/albums/q.../VetteRear.jpg
Last edited by Jud Chapin; Jul 10, 2007 at 10:26 AM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
i just did this and used a suction pump from autozone that cost about $6....it worked great. be sure to use the posi additive when you go to fill it up
Race Director
Joined: Feb 1999
Posts: 19,659
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From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Nice job there Jud. The few times that I have seen this mod, never has it been done where you have put it. Nice work. Got any idea what size tap and plug you used to perform this job. This could be a nice little winter project for some one.
Drifting
Joined: Jul 2004
Posts: 1,695
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From: Kissimmee fl
Finalist 2021 C3 of the Year - Modified
2017 C3 of Year Finalist
Cruise-In VIII Veteran
St. Jude Donor '07
That could be a "R" size drill and a 1/8th pipe tap. Then a 1/8th pipe plug to close things up. With a battery drill, go right in with the oil still in the rear. The oil coming out will flush the chips out after you drill and tap it. 
Melting Slicks
Joined: Apr 2004
Posts: 2,008
Likes: 38
From: Space Coast Gator Territory
QUOTE=kanngaroo jack;1561008884]Went to change the diff oil ' but am i missing somthing. like a drain plug?
80 vette![/QUOTE]
You have some good advice in the posts above. Maybe I can add something useful. Gary, grt1999 has everything you need to know in his Differential Rebuild post. I can't recall all the details, but i have installed drain plugs in two of my differentials. Below is a pic of the first:
[IMG][IMG]
[/IMG][[/IMG]
All the parts were purchased from Lowe's and readily available. I think the sleeve was 3/8 and the removable drain plug was 1/8. Both pieces are in close proxmity bins, so you can check them for compatability. You will need to buy a NPT tap, as the 3/8 sleeve is on a taper. When you cut the threads, be careful you don't go too deep. Monitor the sleeve dept as you go, or the sleeve will rise above the differential floor and prevent all the oil from draining. After you buy the parts look for the correct NPT tap and it should tell you the correct drill bit diameter. The job is relatively easy after you assemble all the parts and tools.
80 vette![/QUOTE]You have some good advice in the posts above. Maybe I can add something useful. Gary, grt1999 has everything you need to know in his Differential Rebuild post. I can't recall all the details, but i have installed drain plugs in two of my differentials. Below is a pic of the first:
[IMG][IMG]
[/IMG][[/IMG]All the parts were purchased from Lowe's and readily available. I think the sleeve was 3/8 and the removable drain plug was 1/8. Both pieces are in close proxmity bins, so you can check them for compatability. You will need to buy a NPT tap, as the 3/8 sleeve is on a taper. When you cut the threads, be careful you don't go too deep. Monitor the sleeve dept as you go, or the sleeve will rise above the differential floor and prevent all the oil from draining. After you buy the parts look for the correct NPT tap and it should tell you the correct drill bit diameter. The job is relatively easy after you assemble all the parts and tools.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
I wish I could take credit for the job. Actually what happened, though, was I took my '76 in to a Vette shop for a rear fluid change back in the 70's and they said that is the way they did them all. I don't know the exact bolt size but I don't think it really matters...it's probably 1/4 inch or so. The mechanic just drilled a hole where you see it and of course all the fluid came out along with any metal residue from the bit. He then tapped it and installed the proper sized bolt. It really works great. I showed this once before here and some of the guys were talking about dropping the rear to do it, but I really think that's a waste of time and energy. Try it and I'm sure you'll like it.
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Pro
Joined: Apr 2006
Posts: 647
Likes: 22
From: Norwalk CT and Boynton Beach FL
I've been told that drilling a hole in the differential casing weakens it and then it is prone to crack. I don't think GM is that stupid and would have put one in if it didn't compromise the strength and integrity of the casing --- but I could be wrong. I will continue to vacuum the differential oil out when it needs to be changed--- which happens once every 10 or 15 years
Drifting
Joined: Mar 2006
Posts: 1,526
Likes: 2
From: Oak Ridge NC
I've been told that drilling a hole in the differential casing weakens it and then it is prone to crack. I don't think GM is that stupid and would have put one in if it didn't compromise the strength and integrity of the casing --- but I could be wrong. I will continue to vacuum the differential oil out when it needs to be changed--- which happens once every 10 or 15 years
I believe that using the vacuum pump gets a lot out of the diff., but leaves the heavy stuff, including any metal particles in the diff. Just my .02.
Last edited by SmokinBBC; Jul 10, 2007 at 11:19 PM.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
I've been told that drilling a hole in the differential casing weakens it and then it is prone to crack. I don't think GM is that stupid and would have put one in if it didn't compromise the strength and integrity of the casing --- but I could be wrong. I will continue to vacuum the differential oil out when it needs to be changed--- which happens once every 10 or 15 years
Mine was done over 30 years and 85k miles ago and is as good as when it was done.
Pro
Joined: Apr 2006
Posts: 647
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From: Norwalk CT and Boynton Beach FL
Thread Starter
Intermediate
Joined: May 2007
Posts: 35
Likes: 0
From: perth wa
[IMG][IMG]
[/IMG][[/IMG]All the parts were purchased from Lowe's and readily available. I think the sleeve was 3/8 and the removable drain plug was 1/8. Both pieces are in close proxmity bins, so you can check them for compatability. You will need to buy a NPT tap, as the 3/8 sleeve is on a taper. When you cut the threads, be careful you don't go too deep. Monitor the sleeve dept as you go, or the sleeve will rise above the differential floor and prevent all the oil from draining. After you buy the parts look for the correct NPT tap and it should tell you the correct drill bit diameter. The job is relatively easy after you assemble all the parts and tools.[/QUOTE]
Thread Starter
Intermediate
Joined: May 2007
Posts: 35
Likes: 0
From: perth wa
thanks to all of your replies. I reley on you guys for your help !
[IMG][IMG]
[/IMG][[/IMG]All the parts were purchased from Lowe's and readily available. I think the sleeve was 3/8 and the removable drain plug was 1/8. Both pieces are in close proxmity bins, so you can check them for compatability. You will need to buy a NPT tap, as the 3/8 sleeve is on a taper. When you cut the threads, be careful you don't go too deep. Monitor the sleeve dept as you go, or the sleeve will rise above the differential floor and prevent all the oil from draining. After you buy the parts look for the correct NPT tap and it should tell you the correct drill bit diameter. The job is relatively easy after you assemble all the parts and tools.[/QUOTE]
Advanced
Joined: May 2007
Posts: 64
Likes: 0
From: Knoxville Iowa
But, if it was easier to change the tranny fluid, most folks would do it oftener, and the filter wouldn't need to be changed as often since a good portion of the glop would get drained out, RIGHT?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
The drain plug in the transmisison pan is just an easy way to get the fluid out so dropping the pan isn't so messy. I do it to all of my transmission pans.
As far as the rear end plug, it's a good idea that even the good rear end rebuilders suggest. It will even allow for a flush to be used to get the thick sludge out before you fill with clean fluid.
I think I would drill and tap for a magnetic oil pan drain plug, to help keep any metal from floating around.