04 FX4 bonestock with 95,000 miles.

I changed my Rear diff oil last night. The problem is my owners manual said I needed 75W-90 so thats what I got (RP). When I was taking the cover off the diff I noticed the tag that said 75W-140 only. I went ahead and put it in but should I be concerned or do I need to change it over to the 75W-140. I dont tow alot and when I do 95% of the time its a lawn mower or Polaris RZR. Any input would be appreciated. Thanks!

 

somebody will confirm, but i think the oil for the front differential is 75-90 and for the rear differential is 75-140. i used 75-140 for my rear differential in my 2wd as per hanes and the same tag in the differential.

i would suggest you get the right oil for the rear and replace it. that its kind of a sensitive part that can get really hot

look here: http://bobistheoilguy.com/forums/ubb...Number=2161052

 

The same differential in my Lincoln calls for 90W GL5, equivalent lubes are 75W90 and 80W90, so you are probably safe so long as you put the truck to light-duty service only.
I changed the lube in the Lincoln recently (170K miles) and put in 75W140 GL5 full synthetic....longevity is the name of the game.

FYI: The axle in the Lincoln exhibits a small amount of wear of the pinion shaft bearings and the wheel bearing races on the axles were a bit rough. Repair bearing assemblies took care of the wheel bearings and a reset of the pinion bearing preload took care of that minor problem.
Whether or not the heavier weight lube would have produced less wear of the axle assembly is a question without a suitable answer. I suspect the answer would have been "yes".

 

My owners manual calls for 75W-90 in both front and rear differentials. So why does it say that and then the rear end had the 75W-140 tag on it. Doesnt make sense to me but I just want to make sure I have what is needed in it.

 

I changed mine out and it called for 75w-140, but my shop didn't carry Royal Purple in that, so I got 85w-140, not a problem so far

 

Technical Service Bulletin TSB 05-23-3 changes the lube for rear differentials to 75W140 GL5 full synthetic.


1997-2005 Expedition, F-150

NOTE WHEN SERVICING THE REAR AXLE ON ANY 2002-2004 F-150, EXPEDITION, NAVIGATOR, EXPLORER OR MOUNTAINEER BUILT BEFORE 3/30/2004, IF FLUID REPLACEMENT IS REQUIRED, REPLACE THE ORIGINAL FUEL EFFICIENT HIGH PERFORMANCE (FEHP) SAE 75W-90 REAR AXLE LUBRICANT WITH SAE 75W-140 HIGH PERFORMANCE SYNTHETIC REAR AXLE LUBRICANT. WHEN THE FLUID TYPE IS CHANGED, REPLACE THE CURRENT "FEHP" METAL TAG WITH A NEW "75W-140" TAG (F3TZ-4121-AA). IN ADDITION, REMOVE OR BLOCK-OUT THE FEHP REFERENCE ON THE MULTI-COLORED LABEL LOCATED ON THE RIGHT SIDE AXLE TUBE. IF THE AXLE IS A LIMITED-SLIP MODEL, USE XL3 ADDITIVE FRICTION MODIFIER IN THE QUANTITY RECOMMENDED BY THE WORKSHOP MANUAL.

That should bring you up to speed.

 

Thats what I needed to hear! Thanks! So its ok in the front diff just not the rear? If so ?I'll just catch what I had in the rear in a clean panand put it in the front.

 

Why would you possibly want to reuse old oil ????? You also have no idea how to fill that front axle, otherwise you'd realize that you can't just pour it in... please,please,please don't reuse your rear fluid

 

Obviously you cant read the whole thread. I just put the fluid in last night. Drove to work this morning. When I get home the fluid will have a grand total of 22 miles on it. I repeat 22. It is not old! Yes I am aware that you can not just "pour" the fluid in the front just as you can not "pour" it in the rear.

Next try to read the whole post before you come out and call someone a idiot!

 

The TSB does not mention a change from 75W90 GL5 for the front differential.

In case you may have missed an earlier post: Wal-Mart Supertech 75W140 GL5 full synthetic is available for $10.50/QT more or less. That puts it about half the price of any of the majors.