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Send PMWest Bend, WI - USA
Joined: 3/18/2010
Posts: 46
Vette(s): 1985 silver coupe & 1975 red coupe
I've got a question for you guys. I bought a 1981 Vette recently and have changed all the fluids except for the rear end. I have read that it's just about impossible to get all the old gear oil out of the thing by the suctioning. I saw a article in a Vette magazine where they drilled a hole in the bottom and tapped it for a pipe plug. There is NO way I'm trying that so What should I do. Thanks, Darrell
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Well I really don't think you want to remove the differential and split the case to drain the fluid. 
So I'd say your going to have to suction it out.
|UPDATED|6/23/2013 7:28:09 PM (AZT)|/UPDATED|
So I'd say your going to have to suction it out. My differential on the '81 was drilled and tapped for a drain plug. It's really not hard to do. The aluminum is soft so tapping threads into the hole isn't a major deal. Just use a brass plug wrapped with some teflon tape and it shouldn't leak.
|UPDATED|6/23/2013 7:28:09 PM (AZT)|/UPDATED|
GEN III 5.7L "LS6" Engine swap
TKO500 5 spd.
3.54 Dana 44
'69 "N11" Sidepipes
Borgeson Steering Box
Born 8/1981
Sequence #3975
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Lifetime Member #26
Borgeson Steering Box
Born 8/1981
Sequence #3975
Click here to see more pics of my Vette on CarDomain.
Lifetime Member #26
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Buy a suction pump (we called them vampire pumps in the Navy). A little hand operated job with a rubber hose. Pull out all you can with it and refill it. It'll be fine.
Isn't the rear end cover cast iron? Don't think I'd try drilling and tapping it. Cast iron doesn't always cooperate...
Don't forget to add the posi-lube additive to the rear gear oil. It'll make noise if you don't add it.
Darryl
Isn't the rear end cover cast iron? Don't think I'd try drilling and tapping it. Cast iron doesn't always cooperate...
Don't forget to add the posi-lube additive to the rear gear oil. It'll make noise if you don't add it.
Darryl
"Let them that don't want none have memories of not gettin' any."
- Brother Dave Gardner
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Former Member
Send PMManteca, CA - USA
Joined: 11/20/2005
Posts: 3623
Vette(s): 1978,two tone,Metalic Rootbeer & gold
1975 L48 4 speed
dyoes said: Buy a suction pump (we called them vampire pumps in the Navy). A little hand operated job with a rubber hose. Pull out all you can with it and refill it. It'll be fine.
Isn't the rear end cover cast iron? Don't think I'd try drilling and tapping it. Cast iron doesn't always cooperate...
Don't forget to add the posi-lube additive to the rear gear oil. It'll make noise if you don't add it.
Darryl
Isn't the rear end cover cast iron? Don't think I'd try drilling and tapping it. Cast iron doesn't always cooperate...
Don't forget to add the posi-lube additive to the rear gear oil. It'll make noise if you don't add it.
Darryl
The 80'-82' batwing carrier is cast aluminum.
Jimmy B.
Just can't wait to get on the road again. 
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22715
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Even with a draining plug, you won't get ALL of the old gear lube out. You'll get more than a suction gun, of course, but still, there won't be enough old stuff left in it to really cause a problem. The trick is to drive the car around for a while and get the gear lube nice and hot, so it will be thin(er), and it'll be a lot easier to suction(or drain) out.
And absolutely do not forget to add the posi additive!
(dam spel-chek :<()
|UPDATED|6/24/2013 10:04:33 AM (AZT)|/UPDATED|
And absolutely do not forget to add the posi additive!
(dam spel-chek :<()
|UPDATED|6/24/2013 10:04:33 AM (AZT)|/UPDATED|
Joel Adams
C3VR Lifetime Member #56 
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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dyoes said: Buy a suction pump (we called them vampire pumps in the Navy). A little hand operated job with a rubber hose. Pull out all you can with it. It'll be fine.
Don't forget to add the posi-lube additive. It'll make noise if you don't add it.
Darryl
Don't forget to add the posi-lube additive. It'll make noise if you don't add it.
Darryl
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Starting re-assembly of rear drive line. Bought fluids for the diff and received 2 bottles of additive. Looking at other posts I see some say add two botlles (4oz) and others say one is fine. What say you VetteExperts? Thanks. (I already have two bottles so I'm inclined to throw them both in - any harm in that?)
Mario
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22715
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Dump them both in. Won't hurt a thing...
Or you can save one for later....either way is fine.
Or you can save one for later....either way is fine.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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What's the verdict on using only the real (GM) thing in regards to posi fluid? Is that a requirement or is additive from the parts house acceptable? (I've always used GM, but just thought I'd ask for future ref)
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22715
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
The GM additive is good, but there are others that are just as good.....and they ALL smell bad. I uses either the GM stuff in the black bottle, or the Lubegard stuff.
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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