[66sprint6]

I was considering changing the gear oil in the differential. And as with most jobs, I have to do it in my driveway. I have a new gasket and can drain no problem. But for filling, I’m wondering if I can get the bottle high enough to drain into the housing. I see that some of the gear oil containers are like a squeeze bottle, so I was thinking of putting a section of tubing on the end and squeezing the fluid into the hole.

[Sirrotica]

I've done it that way for years, it should work just fine for you too.

[66sprint6]

Good to know. Thanks for the input.

[geeteeohguy]

If you have the car on a lift, the rear end will drop down and you can put a tube on the bottle spout and the gear oil will go in easily with gravity helping. Also, set the bottles of lube out in the sun for awhile to thin the lube out so it goes in easier.

[Jeff Hamlin]

FWIW; I use one of those auto store handheld suction guns.
I use to extract and/or add oils on Diff and MT.
No need to pull cover. Unless you want to do a gear inspection this works well.
It's a little slow but minimal mess and works at any angle.

Cheers.

[PontiacJim1959]

I sometimes slip a short length of 3/8" or 5/16" rubber fuel line on the end so it gives you some flexibility and you can get the hose better placed into the fill hole.

When it begins to pour back out of the hole, its filled.

It has been a long time working on a 10-bolt, but I believe you should also find a breather cap on the axle tube, make sure it is clear and functioning as these can get plugged up and cause internal pressure to push oil out of seals.

https://www.ebay.com/itm/1962-81-GM-...-/263847558034

[66sprint6]

Yes, I need to find one of those suction pumps, they're not common around here from what I can find. I do have one of those drill pumps but I'm not sure that it can move anything as thick as gear oil. I do like the idea of not taking the cover off if I don't have to.
Last time I checked the breather cap it was good, but of course now's a good time to check it again. I do have a NOS one if I need it.

[Sirrotica]

I've been in the automotive repair business for over 50 years and have owned 2 suction gums, It's just as easy to put a piece of hose on the gear lube bottle as it is to use a suction gun, been there done that.

You can suck lube up through the hose, but it's easier to just unscrew the end off of the gun and just pour it in, gear oil just doesn't flow easy enough to suction it out of the gear lube bottle. I've actually rolled the rubber seal off of the piston inside of the suction gun trying to suck gear oil from the container.

FWIW, I don't even bother using them with gear oil any longer, I just do what I recommended you do, just use a hose on the end of nipple on the gear oil container, and squeeze the bottle.

[Greg Reid]

I bought one of these for less than 10 bucks total. Threads into a standard anti-freeze jug. I actually bought it to drain and fill a Muncie 4spd but I've used it a couple of times for differentials and it worked fine for me.

[lust4speed]

An additional reason to remove the rear cover besides getting the old fluid out is to see what is on the bottom of the housing and get it out of there. Otherwise most of the stuff on the bottom is going to get stirred back up and pollute the new oil. I like to take a spray bottle of mineral spirits and spray the inside down and get the residual powder and crap flowing out of there.

My track record for having the short length of hose stay on the tapered cap has never been good and the hose usually slips off at least once during the fill. I much prefer the pump that Greg posted. You can get a pump to either fit the smaller quart bottles or the larger pump to fit the gallon jugs. The pumps are cheap and you can store it in a plastic bag until the next fill.

Greg's pump is a little fancier - I never had the end piece and I just loop the hose end into the fill hole.

[66sprint6]

Looks like we’re going to pull the cover. My son wants to do it, so I’ll let him. The only thing I’m wondering now is if I should put a bead of RTV on it when I reinstall with a new gasket.

[propuckstopper]

Originally Posted by 66sprint6

I was considering changing the gear oil in the differential. And as with most jobs, I have to do it in my driveway. I have a new gasket and can drain no problem. But for filling, I’m wondering if I can get the bottle high enough to drain into the housing. I see that some of the gear oil containers are like a squeeze bottle, so I was thinking of putting a section of tubing on the end and squeezing the fluid into the hole.

Try this. Works great:

https://www.amsoil.com/p/severe-gear-75w-110-svt/

[geeteeohguy]

Originally Posted by 66sprint6

Looks like we’re going to pull the cover. My son wants to do it, so I’ll let him. The only thing I’m wondering now is if I should put a bead of RTV on it when I reinstall with a new gasket.

Pulling the cover is wise. Yes, use a sparing bead of RTV on both sides of the gasket. Permatex makes a specific sealer in a green tube for gear oil. I would use that. Also, after you tighten (but not TOO tight) the cover, let it sit overnight to cure before re-filling for best results.

[389]

You either have to open the cover or pull the center section out. Let everything drain and wipe the whole insides down with clean paper towels. Button everything up and put regular 90 weight gear oil. I like Lubriplate. If its a posi get two bottles of posi additive from the local GM dealer and mix that with the Lubriplate 90 weight. Do Not use any other additives..

[Greg Reid]

Just for clarification, I use the pump that I posted but I have never changed differential oil without removing the cover. I use the pump to fill.

[66sprint6]

I ended up finding one of those pumps at an auto supply store. Took the cover off, drained, cleaned the case out. It didn't look that bad, but the gear oil was definitely in need of a change A new gasket and thin bead of RTV, then a new fill. Good to go. There was a number visible on the ring gear.

[Jeff Hamlin]

3:23 Thats what I have behind my '66 with AC
Good ratio.

[66sprint6]

Thanks, Jeff. Still revs like stink on the highway. I couldn’t imagine a numerically higher gear, like 3:55’s.

[GT182]

Valvoline has gear oil for the posi unit with the additive already in it. I've used it in my Jeep GC rear and had no problems. And I'll be using it in the GTO when I change the gear ratio and add an Auburn Limited Slip unit to it. It's really thick and needs to be heated up to get it to "pour" in to the rear housing.

[ZeGermanHam]

If using Valvoline, just make sure you use whatever is needed for your application, since they make gear oil with and without friction modifiers for limited slip diffs.