What do I feed the Rear Diff.? *PICTURES*

[BobWiersema]

I have a small leak in the rear differential. So I thought I would just top it off until the weather allows more time to change the gasket. I looked in the manual and became completely confused. So I looked around here and obviously didn't know what to search for, so I'm still confused about what to put in it. And I would like to get this right before I dump everything to change the gasket.

This is the page from the User Guide under service, fluids or whatever.

So if you read that, you can understand my confusion, or do I just not get it?

They say a picture is worth a thousand words so here is a picture of the rear differential. Perhaps someone can tell by looking at it.

It has a rusty tag that I didn't clean up. Is my answer on the tag?

(Picture is 3meg so don't click it if you use dial up)

I know its starting to get a bit rusty under there (Im so glad I payed for the undercoating and rust proofing) but that's another problem.

If anyone can help that would be great. I dont want to put any more miles on it until I can fill that back up.

Thanks,
Bob

 

[my pos mounty]

You would need to know if you have the limited slip or the open diff first.
Look at the drivers door sticker, under the heading axle. If it starts with a number, then its an open diff, if it starts with a "D" its a limited slip.
Limited slip calls for the 75/140 synthetic (if you drain out the fluid, you need to replace the friction modifier), opens are the 80W90.
Look over your gas tank carefully, thats what your pointing to (blue circle) asking about that leak.
Maybe if that wet stain extends further up, follow it to the end.?.?.?

 

[BK_89iX]

Is your pinion seal leaking and slinging gear oil onto your fuel tank?

If you were leaking fuel to that extent I think you smell it easily.

BK

 

[BobWiersema]

Door Tag

You would need to know if you have the limited slip or the open diff first.
Look at the drivers door sticker, under the heading axle. If it starts with a number, then its an open diff, if it starts with a "D" its a limited slip.
Limited slip calls for the 75/140 synthetic (if you drain out the fluid, you need to replace the friction modifier), opens are the 80W90.
Look over your gas tank carefully, thats what your pointing to (blue circle) asking about that leak.
Maybe if that wet stain extends further up, follow it to the end.?.?.?

Thanks, I will go check that right now and post back.

Thanks again,
Bob

p.s. Stupid gas tank, I don't smell anything but then again I dont pay attention all that much. Isn't that thing plastic? I have never had it out.

 

[my pos mounty]

You would need to know if you have the limited slip or the open diff first.
Look at the drivers door sticker, under the heading axle. If it starts with a number, then its an open diff, if it starts with a "D" its a limited slip.
Limited slip calls for the 75/140 synthetic (if you drain out the fluid, you need to replace the friction modifier), opens are the 80W90.
Look over your gas tank carefully, thats what your pointing to (blue circle) asking about that leak.
Maybe if that wet stain extends further up, follow it to the end.?.?.?

OK, welllll, according to what I read (after posting the above) if you have the 3.73 gear ratio OR the 4.10 gear ratio, you must use the synthetic lube. Friction modifier only if you have limited slip.... So, now you get to decode that number code you saw under the heading "AXLE" on that door sticker.

Explorer
Door Code/open or limited slip/ratio
41....….…… Open 8.8"…...….. 3.27
42..…..……. Open 8.8".….…... 4.10
43..……..…. Open 8.8"…..…... 3.08
44..………... Open 8.8"….….... 3.73
45..…..……. Open 8.8".….…... 3.55
46..……..…. Open 8.8".…….... 3.73
D1..……..…. L/S 8.8".…...…... 3.27
D2...…..…… L/S 8.8".…...…... 4.10
D4...….……. L/S 8.8".…...…... 3.73
D5..……..…. L/S 8.8".……...... 3.55

PS: I thought they are plastic as well. Looking at your pic it appears the the top of the tank is wet as well???

 

[BobWiersema]

Door Sticker

This is the door sticker. I think that's the correct one.
What am I looking for here?

Bob

Give me a minute. Im going out to the garage to fire up the old dell laptop.

 

[my pos mounty]

You have a D4, 3.73 gear ratio, limited slip differential

 

[corkey]

lol, 26 psi tire pressure, didn't get the recall on that sticker done,

 

[Electrohacker]

since you have a D4 you need 75/140 synthetic gear oil and limited slip friction modifier

top off the gear oil only till you can clean it out, no need for a gasket, just used a good tube of black gasket maker LIBERALLY

 

[Electrohacker]

lol, 26 psi tire pressure, didn't get the recall on that sticker done,

neither did my previous owner

 

[Electrohacker]

BTW, replace your spare tire... that firestone is, I'm betting, factory... and waaaaaaayyyyy too old

 

[BobWiersema]

Whats next?

Limited slip calls for the 75/140 synthetic (if you drain out the fluid, you need to replace the friction modifier), opens are the 80W90.

You have a D4, 3.73 gear ratio, limited slip differential

Ok, I hope your not kidding me and a friction modifier is something like a muffler bearing. (I doubt you are). I know my way around the engine, I can take it apart and put it back together but when it comes to transmissions and differentials, I need to ask you guys.

So whats next ?

lol, 26 psi tire pressure, didn't get the recall on that sticker done,

Thats funny, was there actually a tag recall? I never got my money for those Firestone tires. I quit waiting a long time ago.

Bob

 

[Electrohacker]

Ok, I hope your not kidding me and a friction modifier is something like a muffler bearing. (I doubt you are). I know my way around the engine, I can take it apart and put it back together but when it comes to transmissions and differentials, I need to you guys.

So whats next ?



Thats funny, was there actually a tag recall? I never got my money for those Firestone tires. I quit waiting a long time ago.

Bob

small bottle in good parts stores... says "friction modifier" and it IS REAL

there was a recall on the tags due to under-inflation, almost everyone inflates to tag specs

 

[BobWiersema]

Only flat on one side.

Is your pinion seal leaking and slinging gear oil onto your fuel tank?

If you were leaking fuel to that extent I think you smell it easily.

BK

Ill check that tomorrow. Oh I hope not.

BTW, replace your spare tire... that firestone is, I'm betting, factory... and waaaaaaayyyyy too old

What do you mean old? Only 12 years ago I used it when the truck was new.
Its probably flat, why do I carry it around with me.


Bob

 

[Electrohacker]

Ill check that tomorrow. Oh I hope not.



What do you mean old? Only 12 ago I used it when the truck was new.
Its probably flat, why do I carry it around with me.


Bob

tires after 10 years become dangerous, even ones on the shelf. there's growing evidence that the tread can separate and kill you

most tire shops wont sell over 6 years or service over 10 for this reason (and the born on date IS on the tire)

 

[BobWiersema]

Oh, Its in a bottle.

small bottle in good parts stores... says "friction modifier" and it IS REAL

there was a recall on the tags due to under-inflation, almost everyone inflates to tag specs

I forgot about that in the manual, I was thinking it was a part for some reason.

Thanks for the help, you guys are the best.

If anyone ever doubts the talent of the people on this site or the value of being a Elite member, they should read this thread. I have a complete working solution to my problem, and within 56 minutes.

As far as that tag thing goes, now I know why the zeros at sniffy lube would always let the air out of my tires. (That was the last engine, they don't get to touch this one)

Thanks again,

Bob

 

[specialized7]

for that gas leak, check out the vent tubing on top of the diff.
mine was loose and spraying gear oil in the same spot.

 

[BobWiersema]

for that gas leak, check out the vent tubing on top of the diff.
mine was loose and spraying gear oil in the same spot.

Thanks for the tip. Looks like I'm going to be spending some quality time under the truck this weekend.

 

[gijoecam]

I suspect the blue circle isn't a fuel leak, it's the rear pinion slinging the gear lube up, around, and all over the fuel tank. I'd put money on it.

And, for the record, it's definitely a steel tank. I wrestled more than my fair share of them back in my production days at Ford. (I used to build those tanks specifically)

As for the lube, as you discovered, synthetic 75/140 with friction modifier is what it eats.

 

[BobWiersema]

So many leaks so little time.

I suspect the blue circle isn't a fuel leak, it's the rear pinion slinging the gear lube up, around, and all over the fuel tank. I'd put money on it.

And, for the record, it's definitely a steel tank. I wrestled more than my fair share of them back in my production days at Ford. (I used to build those tanks specifically)

As for the lube, as you discovered, synthetic 75/140 with friction modifier is what it eats.

Yep, the pinion seal and cover are leaking. I had a little time today to crawl under the truck and check it out. So fix the leaks and as long as the drive shaft if out, may as well change the U joints. That will dump the trans fluid if I pull the shaft wont it.

I cant believe that tank is made of steel. Whats the logic behind that? Is it tougher? At least its not leaking, I would rather change the pinion seal then have to pull the tank.

Bob