do you have to pull the back cover off to do it? What kind of oil do u put back in? I've got 3.55 ls in the back of my truck.

 

Triton,

I just did mine about 4 months ago. Yes, you have to pull the rear cover off the diff. Make sure you pull it off slowly or you will have fluid all over the place. Once the cover is off and all the fluid has drained out, then clean the surfaces where the cover and the diff meet. There is no gasket here, you just use some gasket goop to make a new one. Then, fill it back up using the hole in the front of the diff. It is not a hard job, just a little time consuming. Total estimate would be about 2-3 hours, depending on your mechanical ability.

Ford recommends 75W140 Synthetic gear lube for the rear end, which is very expensive. If I remember right, you need about 4 quarts to fill the rear end. Check your owners manual.

Before you change the fluid, pull your rear wheels off, as well as the drums, and have a look at the rear axle seals and bearings, make sure everything looks ok. You don't want to fill your diff with that expensive fluid and then find out later you have to drain it all again to replace the axle seals. Seals are cheap, few dollars each.

Hope I helped,
Jeff

 

Hi

Ford recommends 75W140 Synthetic gear lube for the rear end, which is very expensive.

This brings up a question... I went to a dealership last week to change the rear end fluid. They put SAE-80W90 along with friction modifier in it. I have 3.55 with LS. The total came to $58.
It's not exactly what Ford manual says so I did my research and it looks like when you have the LS you can do this kind of fluid.
Question - am I correct ar I am missing something? Do I need to run to the dealership and make them put correct fluid in the rear box?
Thanks!

 

Sorry,
Just found this one

http://www.guarding-our-earth.com/am...-75w-140.shtml

What do you guys think about the second paragraph???

 

AB,

Sorry, that is my goof. I didn't notice that he has the limited slip. I don't have limited slip, so the fluid is different. That sounds right, the fluid and friction modifier in your truck.

That is exactly the fluid I put in my truck, the Amsoil series 2000 75W140 Synthetic.

 

jleinweber,

I actually meant a slightly different thing...

My '97 manual says (even though I have 2X4):

Front Axle - SAE 75W90 plus friction modifier C8AZ-19B546-A
Rear Axle - Ford spec EST-M2C118-A plus the same modifier

And it does NOT say that you should use anything else if you have the LP. It looks like regardless of LS you should use this EST-M2C118-A thing.
And you're correct - the exact match for this would be SAE-75W140.
But from I found over the I-net it looks like you can substitute 75W140 with 80W90...

Am I right on this? That's the question I really want to get answered...

Thanks

 

AB,

Not to sound brash, but you can substitute engine oil in it. The reason for the 75W140 is probably the heat that the gears generate. If you use the 80W90 you are setting yourself up for a gear failure.

Regards

Jean Marc Chartier

 

Ah ha, more controversy! Sounds like the Olympics! Anyways, my Owner's Guide says: Rear axle - Motorcraft SAE 75W140 Synthetic Rear Axle Lubricant 2.6 - 2.7 liters, & Add 118 ml (4 oz) of friction additive modifier for complete fill of 8.8 and 9.75 inch axles. Pages 205 & 208.

BUT..in the Service Guide, pages 18 & 19 (severe duty schedule):

Rear axles containing synthetic lubricant are lubricated for life. Non-synthetic rear axle lubricants should be replaced every 3,000 miles or 3 moonthes, whichever occurs first, during extended trailer towing, etc. The 3,000 lube change interval may be waived if the axle was filled with 75W140 synthetic gear lubricant . Add four ounces of additive friction modifier for complete refill of Traction-Lok axles.

I'm going to assume that my limited-slip (I checked the diff. tag) is a Traction-Lok,... or is it?

BTW - I'm going to use a vacuum pump to suck the old oil out. (so I'm lazy, at least I'm changing the oil!)

 

Sorry,
It's me again Just to close the issue...
I called the dealership I went into to change the fluid and talked to a manager there. Here is what he told me...
The 75W140 was designed for heavy-duty dual-wheel trucks and it does not need friction modifier additive...
For regular maintained single-wheel truck you can put 80W90 along with friction modifier. The recommended service intervals would be 50.000 - 75.000 miles.
Any thoughts on this?
Thanks, Alex.

 

AB,

Your Dealer is full of "S". If your manual recommends 75W140 then your truck should have 75W140. Have him show you the Ford Documents that prove his point. Have him put in writing that he will honor the warranty and pay any expences for out of state occurances because of the wrong oil. The dealer goofed and put in the wrong oil. He just doesn't want to pay to put in the correct oil. If he still refuses have it corrected at another Ford dealer and ask him in writing to reimburse you for the $58.00 you spent having him put in the wrong oil. Send a copy of this letter to Ford.

About the Amsoil thing. The second para states: Most vehicles do not need a 75w140 gear oil. Unless it is specifically recommended, a better choice is typically a 75w90 or 80w90 gear oil. This is a play on words. Did Ford specifically recommend that you not drive into a tree? If not then according to Amsoil your warranty should cover it. Will Amsoil back you up if something fails and you were not using 75W140?

Regards

Jean Marc Chartier

 

I'm with JMC on this one. If the manual calls for it, then use it. I'm pretty sure my manual says 75W140 for open rear end, and 80W90 for LS. But, I'm away from home right now and can't check, but I will when I do get home tomorrow.

 

The LS rear requires 75W140 with Ford friction modifier.

Regards

Jean Marc Chartier

 

OK, here is the end of the story...

After JMC message...

I asked the dealership to provide a doc from Ford saying that 80W90 is a substitute for 75W140. They could NOT find such a thing...

I called like 5-6 dealerships in the area and got mixed response. They split 50 to 50 between 80W90 and 75W140. Only one place told me that I could break the rear end if I put 80W90 in it.

So I went to the dealership and they put 75W140 along with friction modifier into my truck at no cost. The manager told that he usually puts 80W90 in all F-150 and he had no problems what so ever with it. He was convinced that he was doing the right thing...

I think that I am done for 100,000 miles by now. The truck is a little bit slow at acceleration comparing to 80W90...

Many thanks to all of you in helping me out!
Alex.