Mercury Grand Marquis LS 1998

[CARLOS DE LA CRUZ]

Hi guys, I hope someone can help with this. I have a leak on my differential (rear axles) and I want to change the oil at the same time I correct the leak, but I have a doubt, well few doubts:
1.- In the manual is mentioned this is not needed to be checked or change cause this oil cause contains synthetic lubricants and are lubricated for life, only needs to be change if is suspected a leak or submerged in water.
2.- Non-synthetic lubricants should be replaced every 3000 miles or 3 months, whichever occurs first. It can be waived of this is filled with 75W140 synthetic gear lubricant meeting Ford specification WSL-M2C192A, part number F1TZ-19580-B or equivalent. Add 118 ml (4 oz.) of additive friction modifier C8AZ-19B (EST-M2C118-A) or equivalent for complete refill of Traction-Lok rear axles.
3.- In the Capacities and specifications table mentions Rear Axle Fluid is Motorcraft SAE 80W90 Rear Axle Lubricant with the note 1. Such note mentions the use of the Additive Friction Modifier.
My concerns are:
a) If I use 80W90 must be normal oil? And If use such additive every 3000 miles do I need to change it?
b) If I use 75W140 synthetic oil, do I need still using such additive or not?

Thanks

Carlos

 

[meep]

The manual sounds much more picky than the rear differential is. A normal 90 weight gear oil is probably very comfortable without additives for well over 50,000 miles. Plenty of cars never see new lubricant here. I would personally use a synthetic, and if they call for 75-140 that’s fine. Amsoil makes a severe gear 110 weight which would also be a solid option.

is this a limited slip differential? If so it may want a small splash of limited slip additive. If it’s an open diff, no additives are required. If you do use an additive, I don’t see any reason to change this fluid every 3000 miles. That is overkill

 

[CARLOS DE LA CRUZ]

The manual sounds much more picky than the rear differential is. A normal 90 weight gear oil is probably very comfortable without additives for well over 50,000 miles. Plenty of cars never see new lubricant here. I would personally use a synthetic, and if they call for 75-140 that’s fine. Amsoil makes a severe gear 110 weight which would also be a solid option.

is this a limited slip differential? If so it may want a small splash of limited slip additive. If it’s an open diff, no additives are required. If you do use an additive, I don’t see any reason to change this fluid every 3000 miles. That is overkill

Thanks for your quick reply, I don't know if this is a limited slip differential, how can I know that? Where can I find it? If this is a limited slip differential and use 75W140, is needed the additive?

 

[kebabaluba]

The manual sounds much more picky than the rear differential is. A normal 90 weight gear oil is probably very comfortable without additives for well over 50,000 miles. Plenty of cars never see new lubricant here. I would personally use a synthetic, and if they call for 75-140 that’s fine. Amsoil makes a severe gear 110 weight which would also be a solid option.

is this a limited slip differential? If so it may want a small splash of limited slip additive. If it’s an open diff, no additives are required. If you do use an additive, I don’t see any reason to change this fluid every 3000 miles. That is overkill

Traction-Lok is an LSD diff, just a fancy name from Ford. So he should use LSD diff compliant oil if he wants LSD to last.

 

[CARLOS DE LA CRUZ]

Traction-Lok is an LSD diff, just a fancy name from Ford. So he should use LSD diff compliant oil if he wants LSD to last.

Oh nice, yes this is Traction-Lok. So, again, if I use 75W140 synthetic oil, still need the additive mentioned in the manual? or is that just for the 80W90?

 

[michaelluscher]

Most 75-140 gear oils include LSD additive these days
But a bottle of the Ford additive is $10 or so, no reason you can't add it

What's the mileage on the axle, and is this a colder/warmer part of the country?

To be honest, it doesn't really matter, anythings an upgrade over what's in there now
80w90 or 75w140

The way it's worded, you'll have to add the Ford additive XL-3 no matter what Motorcraft gear lube you use
Neither of the Motorcraft gear lubes include LSD additive, whereas some aftermarket fluids do (and will tout it on the bottle)
Price and availability is your biggest decider

 

[kebabaluba]

Oh nice, yes this is Traction-Lok. So, again, if I use 75W140 synthetic oil, still need the additive mentioned in the manual? or is that just for the 80W90?

If i understand your original post correctly, 80W-90 are original fill and it`s synthetic. 75W-140 oil are needed to be deluded with modifier to make it down to original spec. If you use 80W-90 synthetic LSD oil, you are solid.

 

[CARLOS DE LA CRUZ]

Most 75-140 gear oils include LSD additive these days
But a bottle of the Ford additive is $10 or so, no reason you can't add it

What's the mileage on the axle, and is this a colder/warmer part of the country?

To be honest, it doesn't really matter, anythings an upgrade over what's in there now
80w90 or 75w140

The way it's worded, you'll have to add the Ford additive XL-3 no matter what Motorcraft gear lube you use
Neither of the Motorcraft gear lubes include LSD additive, whereas some aftermarket fluids do (and will tout it on the bottle)
Price and availability is your biggest decider
View attachment 184411

Milage is 57375 miles. I am in the north of Mexico, no USA. I am in Monterrey, Nuevo Leon. And depends on the season, lowest temperature is around 23 F and highest maybe 113 F. So, If I use 75W140 synthetic with this additive in it, that's all, right? Thanks

 

[CARLOS DE LA CRUZ]

If i understand your original post correctly, 80W-90 are original fill and it`s synthetic. 75W-140 oil are needed to be deluded with modifier to make it down to original spec. If you use 80W-90 synthetic LSD oil, you are solid.

I don't know really if this is filled with 80W90 or 75W140 and that is my question if whatever I use I need to add such additive. Michaellusher mentioned if I use any motorcraft oil I need to use such additive. So, I guess If I find, as I understand him, a 75W140 Synthetic oil with already in it such additive I will be OK. Thanks Kebabaluba. Regards

 

[LenZee]

Milage is 57375 miles. I am in the north of Mexico, no USA. I am in Monterrey, Nuevo Leon. And depends on the season, lowest temperature is around 23 F and highest maybe 113 F. So, If I use 75W140 synthetic with this additive in it, that's all, right? Thanks

I would go with the 75w140 based upon all the bad axles I've seen in these cars. Also being in a warm climate too.
If it has the additive it will work limited slip or not.

 

[CARLOS DE LA CRUZ]

I would go with the 75w140 based upon all the bad axles I've seen in these cars. Also being in a warm climate too.
If it has the additive it will work limited slip or not.

Excellent, thanks

 

[meep]

Most aftermarket name brand synthetic axle lubricants that I’ve seen will say on the bottle that it has a limited slip additive - so read the bottle. BUT, in my Toyota tundra with limited slip differential, it wasn’t enough. It would chatter a little in tight turns. For it, I also had to add almost a half dose of additive to get it to settle down on tight turns while still keeping some bite when additional traction was needed.

 

[CARLOS DE LA CRUZ]

Most aftermarket name brand synthetic axle lubricants that I’ve seen will say on the bottle that it has a limited slip additive - so read the bottle. BUT, in my Toyota tundra with limited slip differential, it wasn’t enough. It would chatter a little in tight turns. For it, I also had to add almost a half dose of additive to get it to settle down on tight turns while still keeping some bite when additional traction was needed.

Ok, thanks, do you know after motorcraft, what other brand of limited slip additive I can use? Regards

 

[michaelluscher]

Ok, thanks, do you know after motorcraft, what other brand of limited slip additive I can use? Regards

Amsoil and Redline sell one
Lubegard sells several
Motorcraft/Mopar/ACDelco all sell one
K&W, Yukon Gear, ATP, StaLube, BG products

Whatever's easiest/cheapest for you to get a hold of

 

[CARLOS DE LA CRUZ]

View attachment 184683
Amsoil and Redline sell one
Lubegard sells several
Motorcraft/Mopar/ACDelco all sell one
K&W, Yukon Gear, ATP, StaLube, BG products

Whatever's easiest/cheapest for you to get a hold of

Thanks a lot, I will check it. Regards

 

[CARLOS DE LA CRUZ]

View attachment 184683
Amsoil and Redline sell one
Lubegard sells several
Motorcraft/Mopar/ACDelco all sell one
K&W, Yukon Gear, ATP, StaLube, BG products

Whatever's easiest/cheapest for you to get a hold of

What about Lucas, is that ok?

 

[Brons2]

Are you sure it's not a pinion seal leak? Those are fairly common in high mileage rearends.

Regarding the fill for life statements in the manual, not a fan. I have a Ford 9.75" in my Navi with the 75w140 and I change it every couple of years.

 

[CARLOS DE LA CRUZ]

Are you sure it's not a pinion seal leak? Those are fairly common in high mileage rearends.

Regarding the fill for life statements in the manual, not a fan. I have a Ford 9.75" in my Navi with the 75w140 and I change it every couple of years.

Hi, NO, this is the cover only, I already checked it. This is a used car when I bought it, so I downloaded the manual from the internet and I got some doubts on the manual interpretation, such leak came out after running the car for a couple of months. It was storage, don't know how long. But needed new tires and engine oil change and filters. No leaks anywhere until now and only the cover of the differential. And yes, as you mentioned, someone also told me, even manual says that, it is preferred to change the rear axle oil after a couple of year or miles. Thanks for the feedback.