Looking for the best place online to get rear end fluid.. Check all the local auto stores and none of them carry 75w-140 SYN. Would like to get mobile 1 or something better,,already got the friction mod. fluid
any help would be great

 

I too could not find any 75W-140 in my area. I was also looking for the Mobil 1 synthetic. After reading some post here a good amount of people suggested using Royal Purple. So I did, they have 75W-140 full synthetic for $7.99 a qt at northernautoparts.com I also bought the Royal Purple Max ATF trans fluid for my manual trans. It too is full synthetic it was $7.99 a qt. The manual states it needs 3.75qts for the trans but I found it took 4qts. That is being level on the ground and not on any jacks and the manual calls for it to be filled to the bottom of the fill hole (just leaking out).

The rear-end (8.8) requires 5.7pts, or just under 3 qts and you said you already had the friction modifier. Royal Purple gear oil states that you DONT need the friction modifier because its already in their gear oil. I asked Mike from the computer chips forum since he test performance parts and products on the F150 he told me when they add rear-end fluid regardless of brand Royal Purple, Mobil 1, Amsoil etc he always adds the Ford friction modifier anyway and that it won't affect anything.

I just finished doing my the other weekend, no leaks, no noise, no problem I plan on changing my trans fluid and rear-end fluid every 30,000 miles and from what I have read and learned on here as well as other sites is there are many good brands, Mobil 1, Redline, Royal Purple, Amsoil. Pick the one that fits your buget because they are all top quality products, and they all will PROTECT just as well as the other, so if one is $14 and another is $8 then your just wasting $6 on the other product since it is no better in performance and protection then the others.

Another note, if you have the 8.8 rear-end depending on the year it will not have a gasket on it from the factory. There are gaskets out there however no one in my area had any. I asked two Ford dealers in my area and they did not have any and did not stock any. They told me they come from the factory without one and don't need one. When I did mine I used the high temp (orange) RTV silicone. Ford said I could use either that or the blue silicone and should be fine. I just chose to go with the high temp to play it safe. Like I said its been just about a week and I have no leaks at all. I drove it about 20 minutes after sealing it up and filling it up with fluid because I didn't know if you need to insure the friction modifier was mixed in with the other fluid.

 

Good response there XLT.......i usually do several figure "8"s after doing my gear oil to make sure it gets everywhere its supposed to be.Redline also offers synthetic gear lube at or near the same price.Forget that 16-18 dollars a quart for Fords gear lube! www.redlineoil.com

 

Thanks for the info guys,, i'll be ordering fluid and changing my soon

 

ok- so let me get this straight. The motorcraft/Ford gear lube for the rear end is a synthetic fluid? --> I was thinking of putting some SYN in for the winter cold temps (was advised I could improve my gas mileage), but if it's already there, then maybe not... although truck does have 37k on it now.

At what intervals is this recommended???

I do: Engine oil at 3k. tranny at 50. brake fluid at 30. radiator around 40. I only add wiper fluid as necessary...!

 

As long as you dont submerse the differential in water you should be able to go 100k miles before changing it.I did mine at 80k miles and it still looked new.
BTW,if I were you I would cut those intervals in half on the transmission and coolant changes.

 

Yes, it's synthetic. I noticed Wally World, of all places, had some last week. You can also use Richmond www.richmondgear.com/01pdfs/OILVID.pdf and Redline http://www.redlineoil.com/products_g...60&subcatID=20 .