Which oil and gasket do Aerostar differentials require?

[joshhemming]

My 93 2wd Aerostar's rear axle does not have a drain plug, so I have to loosen the housing bolts and drain it the messy way.

The Haynes manual says after draining and cleaning, to put a thin layer of RTV sealant on the housing and install a new gasket. But the repair guide at Autozone's web page says just use a continuous bead of the sealant, and no gasket. Which is correct? I'm thinking the last time I did this I only used the blue sealant and no gasket, but it was 10 years ago and I'm not sure.

Also, I'm not sure about the oil to use. The Haynes manual says use Hypoid oil, and gives a Ford spec. It doesn't give an acual weight. I have an unopened bottle of Quaker State 80-90 GL-5 High Performance gear lube oil which says on the label "provides extreme pressure protection for hypoid gears". Would this be suitable for my diff?

 

[BrooklynBay]

Which differential do you have? The driver's side pillar has a label with the identification code. The differential should have a tag. I would use a gasket with sealant. Rubber gaskets should be applied without any sealant. The owner's manual should state which type of oil to use.

 

[joshhemming]

I'm every bit as much in the dark as I was before.

The door jam label states I have the 24 axle. The owner's manual says the 24 axle is a 3.73 ratio.

As for the recommended oil, the owner's manual says the same as the Haynes manual: Hypoid Gear Lubricant. It gives a couple of Ford part numbers: XY-90-QL or EOAZ-19580-A. Obviously Ford wants everyone to buy THEIR oil, which is probably re-labeled Valvoline or Quaker State, but is double or triple the price.

I still don't know if this Quaker State 80W-90 GL-5 I have on hand, which claims to "provides extreme pressure protection for hypoid gears" would be suitable for my diff. I'm guessing the 90 in the first Ford part number is for 90weight but I can't prove it, and although it doesn't say it's Hyphoid Gear Lubricant, the fact the Quaker State claims to protect hyphoid gears leads me to believe it will be OK.

I used some off the shelf, non-Ford gear oil 10 years ago in it and it hasn't blown up YET. I just can't remember exactly which product it was.

 

[joshhemming]

I did a Google search and came up with an article written by an AMSOIL engineer. It explains the differences in gears and gear oil requirement:

"The differences in gear design create the need for significantly different lubrication designs, which is why manual transmissions sometimes use much different lubrication than differentials. For instance, hypoid gears normally seen in automotive differentials require API GL-5 concentration and performance of extreme pressure additives because of their spiral sliding action."

So GL-5 is definitely designed for the hypoid gears in diffs. I don't know why the owner's manual doesn't say so, instead of just giving their part numbers. Unless it's for revenue generation.

 

[BrooklynBay]

The oil is used for cooling & lubrication, so a dense oil might work better than a thin oil. Synthetic oils have a broader range of operation, so you might want to take a look at Mobil 1 or other synthetic oils.

 

[joshhemming]

Just a followup:

I changed it using Peak 80w90 gear oil which the label said was designed for hyphoid gears. It took just under 2 quarts. $4.99 per Qt. at Pep Boys.

Since I didn't use a gasket when I last changed it 10 years ago, I elected to do the same thing this time. Only instead of using the blue Permatex RTV gasket maker this time I used the one specially made for gear oil applications:

http://www.permatex.com/products/Au...makers/permatex_gear_oil_rtv_gasket_maker.htm

$7.99 at Pep Boys. It seems to have sealed fine.

 

[BrooklynBay]

Thanks for the update! This is a new adhesive, and I didn't see it in the auto parts store near me. How long does it take to dry before you could add oil?

 

[joshhemming]

The instructions said apply it, finger-tighten the bolts until it starts oozing out, then wait one hour to tighten the bolts the rest of the way. So I'm guessing it's considered dry enough in one hour.