rear differential fluid
Thread Starter
Melting Slicks
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From: Construction Sucks! MI
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St. Jude Contributor '03 & '05
rear differential fluid
i just unscrewed the drain plug and nothing came out.
to make sure that it wasn't empty i started putting fluid into the fill hole and it overflowed back out.
is it possible that the fluid is so gummed up that it won't drain out, or is it possible that something is blocking the drain hole? i tried sticking a screw driver in the drain hole, but no residue was on the end of it.
this is the first time that i've changed the oil, so i don't know when it's last been done.
thanks,
joe
to make sure that it wasn't empty i started putting fluid into the fill hole and it overflowed back out.
is it possible that the fluid is so gummed up that it won't drain out, or is it possible that something is blocking the drain hole? i tried sticking a screw driver in the drain hole, but no residue was on the end of it.
this is the first time that i've changed the oil, so i don't know when it's last been done.
thanks,
joe
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From: Lake Havasu City, AZ
Joe,
I have an '88 but I'm confused.... I was under the impression that there is not factory drain hole on the diff and that you need to suck the fluid out with a suction gun....
Perhaps someone drilled a drain hole and tapped it to fit a plug...
But then it should drain especially is the top is open at the same time..
One thought what temperature is it? The 80/90 gear oil is very viscous and it gets like molasses if it's cold out. It might be possible that it is too thick to drain...... Did you run the car for several miles to build up heat in the differential?
I have an '88 but I'm confused.... I was under the impression that there is not factory drain hole on the diff and that you need to suck the fluid out with a suction gun....
Perhaps someone drilled a drain hole and tapped it to fit a plug...
But then it should drain especially is the top is open at the same time..
One thought what temperature is it? The 80/90 gear oil is very viscous and it gets like molasses if it's cold out. It might be possible that it is too thick to drain...... Did you run the car for several miles to build up heat in the differential?
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Unless somebody has installed a differential drain plug, there is no separate factory "drain plug". The hole you see on the right side of the differential is used to suck the gear oil out and then refill.
Use a good grade of SAE 80W for 80W-90GL5 and 4 ounces of GM Limited Slip Additive. Once you suck out all of the old oil, add the additive and enough gear oil until the new oil just beging to flow back out of the hole.
Use a good grade of SAE 80W for 80W-90GL5 and 4 ounces of GM Limited Slip Additive. Once you suck out all of the old oil, add the additive and enough gear oil until the new oil just beging to flow back out of the hole.
Thread Starter
Melting Slicks
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From: Construction Sucks! MI
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well that's weird, chiltons shows a picture of a drain plug (which i unscrewed and nothing came out).
that makes sense on what you guys said then. here's a scan of what is says. I really need to get a real service manual.
that makes sense on what you guys said then. here's a scan of what is says. I really need to get a real service manual.
Team Owner
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Fig 190 in the pic doesn't make any sense at all to me. It looks like just one of the differential carrier bolts that holds the housing in place.
I don't recall any threads on the Forum regarding draining differential lube through a "factory" drain plug. There are aftermarket plugs available that requires drilling a hole at the bottom of the case and threading it and istalling a plug.
I don't recall any threads on the Forum regarding draining differential lube through a "factory" drain plug. There are aftermarket plugs available that requires drilling a hole at the bottom of the case and threading it and istalling a plug.
Thread Starter
Melting Slicks
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From: Construction Sucks! MI
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St. Jude Contributor '03 & '05
Originally Posted by bogus
same here... where do those instructions come from?
i've been pumping it out (giving my shoulders a rest). the fluid is pretty nasty. almost a green color with a nice metallic shine.
what a pain in the rear end...literally.
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
I have a C4 Haynes manual that somebody gave to me and it has a pic very similar to 190/191 but without the hand and the section description says it's a carrier bolt. There is no mention in the Haynes book of a specific drain plug on the differential.
The GM service manual and the maintenance schedule in the owner's manual shows differential fluid replacement at 7500 miles along with a new bottle of limited slip additive, but there is no other service recommendation for the differential fluid after that point for "normal driving".
If you drive the car real hard or do track days or lots of autocross, you might want to do a fluid change every season. It's a PITA to do but at least the materials cost is not a lot.
The GM service manual and the maintenance schedule in the owner's manual shows differential fluid replacement at 7500 miles along with a new bottle of limited slip additive, but there is no other service recommendation for the differential fluid after that point for "normal driving".
If you drive the car real hard or do track days or lots of autocross, you might want to do a fluid change every season. It's a PITA to do but at least the materials cost is not a lot.
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Melting Slicks
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From: Construction Sucks! MI
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Originally Posted by c4cruiser
I have a C4 Haynes manual that somebody gave to me and it has a pic very similar to 190/191 but without the hand and the section description says it's a carrier bolt. There is no mention in the Haynes book of a specific drain plug on the differential.
The GM service manual and the maintenance schedule in the owner's manual shows differential fluid replacement at 7500 miles along with a new bottle of limited slip additive, but there is no other service recommendation for the differential fluid after that point for "normal driving".
If you drive the car real hard or do track days or lots of autocross, you might want to do a fluid change every season. It's a PITA to do but at least the materials cost is not a lot.
The GM service manual and the maintenance schedule in the owner's manual shows differential fluid replacement at 7500 miles along with a new bottle of limited slip additive, but there is no other service recommendation for the differential fluid after that point for "normal driving".
If you drive the car real hard or do track days or lots of autocross, you might want to do a fluid change every season. It's a PITA to do but at least the materials cost is not a lot.
i thought this part was going to be easier then changing the filter and fluid on the 4+3 overdrive.
that actually went pretty smooth.thanks everyone for your help.
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From: Lake Havasu City, AZ
As in my earlier post, part of the problemis the high viscosity of the 80W90 gear oil in Northern climates..... wait until it is over 60 degress, drive the car for at least 20 minutes to let the friction heat the gear oil... it will suck out a lot easier...
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Those Chiltons guys are wishful thinkers. They must have gotten ahold of a modded car.
The diff fluid should come out dark green, the additive does that. Metallic is bad though!
That 7500 mile change is to be after the breakin period. After that, it should last a long damn time if it doesn't leak out. Most cars NEVER get the rear end or manual trans oil changed during their lifetimes. I wonder if Jiffy Lube even has it on their price list.
The diff fluid should come out dark green, the additive does that. Metallic is bad though!
That 7500 mile change is to be after the breakin period. After that, it should last a long damn time if it doesn't leak out. Most cars NEVER get the rear end or manual trans oil changed during their lifetimes. I wonder if Jiffy Lube even has it on their price list.
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From: San Pedro CA
Originally Posted by SHINOBI-X
seems like that books a little mis-leading huh?
This is a simple DIY project. Go to Pepboys and pickup a cheap little hand pump - the Mighty-Mite - it's about $10.00. Also get some 75-90wt gear oil whilst there.
At your GM dealer, get 2 - yes 2 - bottles of diff additive. Gordon Killebrew recommends 2 bottles.
Jack it up, remove the fill bolt (17mm allen, if I remember rightly) use the pump to remove the oil, reverse the flow and pump in the additive bottles, then the gear oil.
Done.
Takes longer to jack the car up.
