Hey guys, gettin ready to change rear diff fluid in my 05 for the first time( hate to admit to that) and I'm @65,000...I do a fair amount of fishing, and when launching the boat, the rear diff is sometimes half submerged..No problems yet(knock on wood)..How often do you think it should be changed in my situation, and is RTV alone gonna give me the best waterproof seal?
Thanks in advance,
Nate

 

You should be fine, I believe Ford recommends 100k on these trucks before you need to change them. But I would occasionally open up the fill cap and check to make sure water didn't get in.

RTV is all I use when I put mine on. Also if you have a limited slip don't forget to get a bottle of the friction modifier. You will need 3 qts of 75w140 gear oil for it as well.

 

Thanks...Just hadn't heard anything about diffs getting submerged frequently, so figured
I'd ask..As always, you guys and this site are a huge help!!

 

You are probably ok with the water b/c there is a hose on the vent that goes up to the bottom of the bed. The diff could actually be completely under water and still not have an issue.

While you are changing the fluid just inspect the breather hose and you should be good to go. There is what looks like a "T" for the brake lines with 1 rubber hose going up in front of the spare tire.

 

if you are getting the rear diff into the water every now and then..... i would at least make it a habbit to check the condition on the diff fluid every time you change the oil. just pop the fill plug and stick it with an allen key. if its milky change it immediately.

 

My pinion seal is leaking on my 05 3.73 Limited Slip. Only 32k miles on it too...grrrrr. For the life of me I cannot get the plug loose to check the level of the oil. Is it reverse threaded?

I was able to draw air out of the vent hose so I don't think it is clogged.

 

you just need a bigger breaker bar they are cranked in there pretty tight from the factory.

 

Maybe I'll have my sister-in-law do it... she can put a lot of A$$ behind it.

Thanks papa

Just got it out..... put a pipe on the ratchet to get it off...... Red Loc-tight was the culprit. I thought is was rather presumptuous of them to use Loc-tight considering after 32k miles I need to replace the pinion seal

 

If you have a traction lok, I wouldn't mess with it until it started chattering when turning corners. If you don't have traction lok change it whenever you wish.

 

i just changed mine had to go to the dealer and get 4 quarts of 80$ fluid 75w 140 and the a 5$ bottle of additive my diff only took about 3.5 quarts but it was not a fun process

 

Well, while on vacation down @ Dale Hollow lake my pinion seal decided to start leaking....What am i looking at, as far as cost goes from the dealership?... It leaked
about 6oz on a 4.5 hour drive pulling our boat....Is this something I could fix myself
in the future? I'm about a 5 out of 10 mechanically, and have a pretty decent amount of tools... Thanks as always!!
-Nate-

 

In the past I would have "tried" done it myself... but with these new fluids and tools needed to perform the job I figured it would be safer to have a pro do it. I fortunate enough to have a cousin that does that sort of work so we will do it this weekend. Since I only have 32k miles on the truck I don't want to risk screwing things up. I already brought the fluid (synthetic) at Wal-mart for just under $11.00 per quart. They did not have the modifier though.