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I just did a search and read that the differential fluid should be changed every 100,000 miles. My car is almost there, so I'd like to know the specific type of fluid I should use.
If anyone can recommend a brand too, I will appreciate it!!

Thanks!
 

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Fry Rice Specialist
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i'm curious too....
 

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From the 1993 Service Manual (8.8" gear - 7.5" gear similar):

All conventional axles use XY-90-QL (ESP-M2C154-A) lubricant or equivalent, plus 4 ounces of friction modifier additive EST-M2C118-A (C8AZ-19B546-A) or equivalent for Traction-Lok axles. Always fill rear axle to bottom of filler hole.

Side note: 7.5" gear lubricant capacity is 2.5 pints, whereas the 8.8" gear lubricant capacity is 3.25 pints.
 

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I've run Ford and Valvoline oils, 80W90 (w/ the friction modifier).

I've also discovered that the Trak-lok rear ends should be changed more like every 25,000 to 30,000 miles. They seem to stop working if run longer than that.
 

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Silver95Bird said:
I've run Ford and Valvoline oils, 80W90 (w/ the friction modifier).

I've also discovered that the Trak-lok rear ends should be changed more like every 25,000 to 30,000 miles. They seem to stop working if run longer than that.
looks like I have an excuse to try out Royal Purple and Redline:)

joseph
 

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Does Royal Purple require the Friction Modifier also? I'm putting a used trac-loc in tomorrow (maybe even today) and need to know BEFORE putting it in. :D

Thanks

Edit: Also, can the friction modifier be purchased anywhere but the Ford Dealer. I'm not a patient person (I know, its a virtue and all) and would like to get it this weekend if I need to. (I.E. O'reilly's)
 

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i use royal purple and it already has the friction modifier in there. i bought it from independant part store. need 2 bottle and that's still a little bit left in the bottle once fill up.
 

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unless you have a limied slip diff you don't need friction modifier. And if you use mobile one (some other brands too) you don't need friction modifier either. When I used friction modifier (not even a whole bottle) with my LSD there was hadly any holding power between the wheels. Less than 75 ft-lbs (less than 15k on the LSD). I flushed it and put straight mobile 1, much more holding force. No shuddering or any type of roughness either. No fore friction modifier for me, mobile one and I'm good to go for another 25K. I flush it often, it cant' hurt and it's easy with a suction pump.
 

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Hello all,

Hate resurrect a old thread like this.

Can I find the needed info from my T-birds VIN or some other stamped/ stickered info that does the car have a LSD or not?

Car is base model V6 1992.

I have mineral based 80-90W rear end oil at my garage. Several litres of it. Can I use it safely? Extreme Pressure and API GL5 class.

Thanks.
 

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On the door sticker, there's an AXLE code; the chart is available from the articles here (specifically TCCoA Tech Articles ). On the diff itself should be a tag; if, for instance, it's got "3 27" on it it's an open 3.27; if it's got "3L27" it's a LSD 3.27. (Mine says 3L08 due to being a limited slip 3.08). I'll bet your 1992 base is non-LSD, though.

If all else fails, crack the case open and visually examine it.

80-90W? That's unusual; 80W90 is a lot more common. You're saying it's 80 viscosity normally, but 90 in the winter? That's kind of bass-ackwards.

RwP
 

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The Trak-loc diffs should have the fluid changed semi-regularly, to get the old clutch material out of there. Or when it's taken apart to replace the clutches.

On an open diff, I wouldn't change it. There is a greater chance of getting the wrong type or amount of fluid in, or starting a leak, than there is having something happen because the fluid is too old. My old 95 T-Bird had 220k on the original fluid, my 88 had 206k, and Brenda's old Cougar had 187k. Whisper quiet.

A fluid change on these cars is not fun, or easy with no drain plug. That's why guys pre-fill the diffs before installing them!

Al
 

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Yeah 80W90 diff oil. You got my point, sorry for the wrong place for letter W. Duh :)

My older Capri rear diff oil change is messy too. You need to open the diff case back plate and spill out the oil that way.
Push in the new oil with tubing and a cylinder tool. Have those.

If I read correct, T-birds casing can be opened the same way.

I do think that new oil is good to change, and I do not even know the diff oil change history for this vehicle.

Thanks
 

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You have to support the diff before removing the cover, and it is imperative to torque the bolts when re-installing the cover, since all the weight is on that cover.

Al
 
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