96 Differential Fluid Change
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From: Maryville Tn
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The differential plug is in the right side of the case. There's no drain plug...It has to be suctioned out. I took my '85 and '93 to the local Valvoline quick lube to have the fluid swapped out. I supplied the GM 75w-90 lube and 2 bottles of limited slip additive. Took a couple of minutes. Any lube that's the right weight should do. 
Melting Slicks
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From: Delta B.C. Canada
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You can also buy gear lube that already has the additive in it.
Oh, and you'll need to pump the new fluid in with the same pump you used to suction it out.
Oh, and you'll need to pump the new fluid in with the same pump you used to suction it out.
Intermediate
Joined: Mar 2012
Posts: 35
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From: Stafford VA
I've seen in the past where mechs will remove the bottom few bolts from the diff cover and separate the cover from the diff housing just enough to let the fluid drain out.
What are everyone's thoughts on that method?
I know that it can lead to having to replace the gasket (assuming they used one on the corvette) but I always thought that if it was time to change the fluid the gasket could probably stand to be replaced as well.
What are everyone's thoughts on that method?
I know that it can lead to having to replace the gasket (assuming they used one on the corvette) but I always thought that if it was time to change the fluid the gasket could probably stand to be replaced as well.
Safety Car
Joined: Jun 2006
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From: FL
I've seen in the past where mechs will remove the bottom few bolts from the diff cover and separate the cover from the diff housing just enough to let the fluid drain out.
What are everyone's thoughts on that method?
I know that it can lead to having to replace the gasket (assuming they used one on the corvette) but I always thought that if it was time to change the fluid the gasket could probably stand to be replaced as well.
What are everyone's thoughts on that method?
I know that it can lead to having to replace the gasket (assuming they used one on the corvette) but I always thought that if it was time to change the fluid the gasket could probably stand to be replaced as well.
Race Director
Joined: Apr 2003
Posts: 17,700
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From: moraga ca
Not really practical on a C4, the diff cover is the batwing attached to the structure of the vehicle, there is no gasket the batwing is sealed with RTV. My preference is to install a drain plug, see my post #4 in this link http://forums.corvetteforum.com/c4-t...questions.html for an easy modification that will make service much easier.
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What cover?
Have you actually looked at it?
Go to the parts store and buy a big suction gun. Get the tubing and fittings to get down to a hose size small enough to fit well inside the fill hole. You MUST get the hose deep within to get fluid OUT.
Suck out as much as you can get. Fill with fresh...in fact if its never been serviced, over fill and suck out that fluid again. Do all this AFTER a drive to warm the fluid so it can be suctioned out.
While its low add your GM additive or fill with fluid that contains the additive. Fill, plug and forget.
OR
go to Iffy lube and take a chance that the zit-farmer kid there remembers to fill the thing after he sucks it dry...they often forget when they stop after 3 minutes of work for a smoke..
The Last time I went to one of these sh!thole places they lost my filler cap then argued with me about it when I returned 5 minutes later with oil all over my engine and no cap and the dipstick laying across the engine...
never again.
Thats why God gave us parts stores...so simple chores like this could be done right.
Have you actually looked at it?
Go to the parts store and buy a big suction gun. Get the tubing and fittings to get down to a hose size small enough to fit well inside the fill hole. You MUST get the hose deep within to get fluid OUT.
Suck out as much as you can get. Fill with fresh...in fact if its never been serviced, over fill and suck out that fluid again. Do all this AFTER a drive to warm the fluid so it can be suctioned out.
While its low add your GM additive or fill with fluid that contains the additive. Fill, plug and forget.
OR
go to Iffy lube and take a chance that the zit-farmer kid there remembers to fill the thing after he sucks it dry...they often forget when they stop after 3 minutes of work for a smoke..
The Last time I went to one of these sh!thole places they lost my filler cap then argued with me about it when I returned 5 minutes later with oil all over my engine and no cap and the dipstick laying across the engine...
never again.
Thats why God gave us parts stores...so simple chores like this could be done right.
Last edited by leesvet; Jul 2, 2012 at 12:12 PM.
Le Mans Master
Joined: Oct 2007
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From: Akron Ohio
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This is the oil I would recommend:
AMSOIL Severe Gear 75W-90
http://kahunamotorsports.com/svg-product-page.html
The AMSOIL has the posi additive in it so no need to add anything more. I use it in my race car and have no issues.
As for a drain, I drilled the bottom of my carrier and tapped it for a 1/4" NPT plug. Be sure to drill with it full of fluid that way as the fluid drains it will flush out the chips as well. Very simple job.
AMSOIL Severe Gear 75W-90
http://kahunamotorsports.com/svg-product-page.html
The AMSOIL has the posi additive in it so no need to add anything more. I use it in my race car and have no issues.
As for a drain, I drilled the bottom of my carrier and tapped it for a 1/4" NPT plug. Be sure to drill with it full of fluid that way as the fluid drains it will flush out the chips as well. Very simple job.
Race Director
Joined: Apr 2003
Posts: 17,700
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From: moraga ca
This is the oil I would recommend:
AMSOIL Severe Gear 75W-90
http://kahunamotorsports.com/svg-product-page.html
The AMSOIL has the posi additive in it so no need to add anything more. I use it in my race car and have no issues.
As for a drain, I drilled the bottom of my carrier and tapped it for a 1/4" NPT plug. Be sure to drill with it full of fluid that way as the fluid drains it will flush out the chips as well. Very simple job.
AMSOIL Severe Gear 75W-90
http://kahunamotorsports.com/svg-product-page.html
The AMSOIL has the posi additive in it so no need to add anything more. I use it in my race car and have no issues.
As for a drain, I drilled the bottom of my carrier and tapped it for a 1/4" NPT plug. Be sure to drill with it full of fluid that way as the fluid drains it will flush out the chips as well. Very simple job.
Thread Starter
Intermediate
Joined: Jun 2012
Posts: 49
Likes: 2
What were GM engineers thinking, tells us to change fluid and put no drain plug in! Oh wait... that is what Mister Goodwrench is for in their minds! guess they woke up when C5 came out, they have a drain. Anyways bought a suction/refill pump for $10.00, and i am going to put in Valvoline 80-90 G5 Limited slip gear lube in. I looked at Amzoil severe duty, but it has on the bottle "if there is gear chatter add Amzoil limited slip additive" Also ,And i'm sure this will cause a debate but on a Corvette article on how to rebuild a differential, they did not want synthetic gear oil in the case. If I find the article I will post it. I dont race, my Vette is a showcar and Sunday driver, so extreme situations dont apply for me, thats why i'm going with the Valvoline. Lots of great input on this issue, Thanks Guys!
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Burning Brakes
Joined: Dec 2008
Posts: 1,021
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From: Morgan Hill and Marina California
In http://forums.corvetteforum.com/c4-g...rans-diff.html
85MikeTPI was good enough to point out:
http://www.summitracing.com/parts/SPE-5971/
Unfortunately, no longer on $20 special and now back up to $50.
But I got mine. Will be using it tomorrow, maybe tonight, to pump
the 3 gallons of driveline lube in my DD Pathfinder.
Summit should sell just the pump for $20.
Chuck
85MikeTPI was good enough to point out:
http://www.summitracing.com/parts/SPE-5971/
Unfortunately, no longer on $20 special and now back up to $50.
But I got mine. Will be using it tomorrow, maybe tonight, to pump
the 3 gallons of driveline lube in my DD Pathfinder.
Summit should sell just the pump for $20.
Chuck