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I was planning on changing out the gear oil on my rear differential. Nothing wrong, just preventative maintenance since I have no idea when it was done last. The car is a totally stock 1963 Galaxie 500 Sedan with 352, Cruise-O-Matic, and 3.00 rear end. What gear oil weight should I use? The manual recommends straight 90 but that was obviously before synthetics existed. Car is a semi-daily driver. Thanks in advance.
 

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geoffunkle,
Didn't mean to be short. I think the oil they used 50 years ago will allow the your rear gear to go another 50 years.
 

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I sure hope synthetic oil has changed. Had an F150 rear end built for my '64 Gal. Asked the manager of Advance Auto, who is pretty informed, what he would suggest. He said Royal Purple synthetic 75w150 is what he would suggest in the rear end. In my engine, which will not see very many miles in a year, he suggested using Castrol Tection Extra, 15w40 which is the same as Castrol Deisel oil. Not to waste my money on synthetic oil in the engine.
 

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I have Royal Purple oil in my engine and rear end right now.

But I can certainly understand why one would not use it based on one company releasing a bad product over 20 years ago. Yeah, that totally makes sense.
 

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Discussion Starter #6
I'm not really too concerned with synthetics rusting out my system. I think they solved that problem a long time ago. I am really more concerned with getting the ideal performance and protection for my rear end.

I didn't see any straight 90 gear oil at the auto parts store. I only saw 80w90, 85w90, 75w140, etc. I would assume the 80w90 or 85w90 would be fine for my car.

So if I were to go with a synthetic gear oil, what oil weight would you recommend? Again, the original shop manual and owners manual (albeit written in 1962) call for straight 90.
 

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Discussion Starter #8
I decided to go with Royal Purple for my differential, but they only had the 75W-90 at the store. Is this weight okay to use?

I would think it would be fine. My thinking is that the 75W would still be thicker cold than a straight 90 would be when hot. And when it's warmed up, it will act the same as a 90 weight. So I will be within lubrication spec, and will get better lubrication when cold than with the straight 90.

So I should be good, right? Correct me if I'm wrong. I'm about to change out the oil today.
 

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I agree with the other posters that standard gear lube is all you need, especially since it does a better job of clinging to the gears thereby softening the engagement. For that reason, most drag racers still use standard gear lube.
 

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I decided to go with Royal Purple for my differential, but they only had the 75W-90 at the store. Is this weight okay to use?

I would think it would be fine. My thinking is that the 75W would still be thicker cold than a straight 90 would be when hot. And when it's warmed up, it will act the same as a 90 weight. So I will be within lubrication spec, and will get better lubrication when cold than with the straight 90.

So I should be good, right? Correct me if I'm wrong. I'm about to change out the oil today.
I believe the multi-weight atributes would be the same as with engine oil. 75 is the cold viscosity and 90 is the hot viscosity, so it should act like 75 weight oil when cold and 90 weight oil when hot. If you don't drive the car regularly at 40 below, then you won't benefit much from wide ranging viscosities. The closer the numbers are to each other may be better in your situation.
 

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Discussion Starter #11
Well, they did not have straight 90 or 85w90 at the store. The closest they had at O'reilly was 80w-90, but it looked like a cheap brand so I decided to go with the Royal Purple 75W-90. I could return it I guess and try a different store. This car definitely never sees 40 below zero. I live in Central California by the beach and the temperature is very rarely below 40 or above 85.

Another question. How do you get the plate off the differential to let the old oil out? I was expecting to see bolts like on my truck, but there are none. There is absolutely nothing in the Ford Shop Manual about it. I tried to pry it off with a flathead screwdriver, but was unsuccessful...
 

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Another question. How do you get the plate off the differential to let the old oil out? I was expecting to see bolts like on my truck, but there are none. There is absolutely nothing in the Ford Shop Manual about it. I tried to pry it off with a flathead screwdriver, but was unsuccessful...
Best of luck
 

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I have Royal Purple oil in my engine and rear end right now.

But I can certainly understand why one would not use it based on one company releasing a bad product over 20 years ago. Yeah, that totally makes sense.
You're right, that don't make sense.
 

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Discussion Starter #16
Without going too much into what brand is better than others, synthetics vs. blends, vs. dino oils, etc. My original question is what weight is ideal for my application? The car is a stocker and does not ever see racing/ extreme operation besides me occasionally taking it on some back roads to floor it and scare the crap out of whoever else is in the car :D

It also will never see snow or over 100 temperatures, since I live in an extremely mild climate.

I put less than 3,000 miles a year on this car so I am looking for a good quality gear oil that will last 10 years or so until the next diff oil change.
 

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Discussion Starter #18
I get the point Jim, you recommend 85-90 or straight 90 weight for the rear end. Thank you for the advice and I will follow that recommendation. Not sure why you felt compelled to go back and edit your prior posts though...

Another problem has unfortunately arisen though. Since I couldn't get the cover off, I elected to pump out the oil through the fill hole with a small hand pump. Everything was going swimmingly until the little plastic hose came off the pump and went into the differential. :bicker:

After about 45 minutes of trying to fish the hose out with a coat hanger, I've given up. I need to get the cover off. Any tips on how to get it off would be appreciated.
 

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It doesn't have a cover really. In order to remove the part that is bolted on you have to remove the axles and the drive shaft and then you can remove the 3rd member, hogs head, pumpkin or whatever you may want to call it. It is very heavy and you don't want to drop it so it would be a good idea to have a jack under there to assist you. I'm not sure what they weigh, maybe 50 lbs or so. I've carried them around and all i can say is they aren't light!

Another way some drain the oil is to remove the axle on one side and jack the opposite side of the car way up so it pours out the other end. You won't get it all out that way but it will get a lot of it. While you're at it you could replace the seals. If you've never removed an axle it's easy also. There are only 4 nuts holding it there. There is an access hole in the end of the axle, can't think of the technical name but you'll see it when you remove the wheel. Remove those 4 nuts and you can usually just get hold of it and yank on it, it will slide right out.

Wish i could think of a way to fish that hose out of there! But only thing i can think of is to keep trying to fish it out using one of those flexible grabber tools. They are pretty cheap at the local parts stores. They are about a couple feet long and look like a choke cable, push on the plunger at the end and 4 prongs come out the other end to grab things. They are great to have around for those wrenches, bolts, nuts whatever that get dropped in a place that is difficult to get your hands into. A telescoping magnet thing is another good one and those sometimes are only a dollar or two. Won't work on the hose issue but while you are there might as well grab one. :)

Knew there'd be a how-to out there somewhere. This should make more sense with pictures! Some nasty oil in this one! He removed the brakes and all but you shouldn't have to. I didn't mine.
http://www.ford-trucks.com/forums/1049589-9-inch-oil-change-pics.html

And this link shows tipping the axle like i mentioned and also you can see the brakes are still on there.
http://www.jpmagazine.com/techarticles/drivetrain/154_1110_swapping_a_junkyard_ford_9_inch_axle/photo_07.html
 

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After about 45 minutes of trying to fish the hose out with a coat hanger, I've given up. I need to get the cover off. Any tips on how to get it off would be appreciated.
It would serve you well to use patience right now. Pulling the rear end apart isn't an option you want to take unless absolutely necsesary. Use small chain dipped in grease, use flexable fingers etc.
Also, I'm sorry about re-editing my posts. I get aggravated when talking about synthetic oil. I'd like to have a product that I could advertise as the greatest product ever invented, resonably assume the people I sell it to won't sue me and are unable to prove my product caused them damage. Exxon Mobil and ALL oil companies to this day won't make a pure synthetic oil for piston engine aircraft because they deal with wealthier people that do have the resources and organizational structure to sue their asses off.
 
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