cosway

Rear Axle
Transfer case

Should I change these lubes? What brand is best? any special methods?
doing tranny so thought about this as well.

thanks
2004 5.4L
137,000 K's / 85,000 miles

Fbcoach

Subbed. I was thinking the same thing!

techrep

iTrader: (1)

Front and rear diffs... 75W-140W ..I used Mobil 1 plus 4 oz. friction modifier if you have a limited slip rear end.
T-Case get's merc V same as tranny I believe
and yes 85K I would change them all...

ford4wd08

T-Case technically calls for original Mercon, but since you can't buy it anymore, ford has come out with a T-case specific fluid. Mercon V is supposed to be backwards compatible, so I guess it could be used in the T-case as well.

homer

My transmission leaks into my t-case anyways so I just run Mercon V in both LOL (https://www.f150forum.com/f4/transmi...problem-91809/). I'm plagued with the unfortunate seal between the trans and t-case leak issue.


My dealer says it's fine (Mercon V), I've been running it for quite a few miles that way with no issues. The leak is slow but I pull the T-case fill hole once in a while to relieve then top off my transmission.


Reading my owners manual (maintenance schedule) though (also at http://www.fordservicecontent.com/Fo.../05frdmg4e.pdf for my 2005), it says 150,000 miles for the front and rear differential. Personally, I don't like the idea of leaving it that long ... I guess if you don't use 4x4 much and your IWE's (hubs) are disengaging properly your front differential shouldn't spin in 2WD and therefore shouldn't generate heat, break the oil down, etc... The rear, I'd still want to change that anyways. Having wrote all of that though .... The owners manual (http://www.fordservicecontent.com/Fo.../05f12og1e.pdf) on page 294 states your axles are filled with synthetic lubricants and are considered good for life......... I don't feel I agree with that entirely LOL. I still did mine for peace of mind, around the same mileage as you.

FrozenTundraGuy

I used Mobil 1 Gear Lube in Rr axle, along with the friction modifer from my Ford Dealer. I also used Mobil 1 ATF in trans and very happy with it. Gas mileage appeared to go up slightly and shifts better. Don't put more than 4qts in, otherwise you'll have to drain some out. When I changed mine @ 30K, I was amazed by the crap stuck on the magnet in the pan. I use mine to tow a 5000lbs trailer, so its going to be every 30K. The pan gasket is reusable, good thing as my filter kit had the wrong one. Also recommend you change your fuel filter also if its never been changed. Good Luck