Hello,

My 97 F150, 4x4, 4R70W, 105K miles runs great. I just purchased a 4000 lb camping trailer and am wondering, should I change out the fluid that's in there? I've read where it should be done at 100K and also that it's good for the life of the vehicle, as long as it (diff.) hasn't been under water, which mine hasn't. What do you guys think?

Thanks,

KC

 

Change it. Don't forget to add the friction modifier if you have a LS rear end. Or use gear oil that has the modifier in it already.

Draining and refilling with fresh fluids never hurts anything but your wallet.

 

I changed my gear oil at 60k on my truck. It ran so much better. Definitely do it. Your truck will thank you and it will drive like its brand new if you have LS.

 

It is LS... and thanks for the reminder of the Friction Modifier. :-)

 

Not sure which friction modifier you all are referring too, but I changed mine at my 100K and use BG's.....world of difference, just in they way it felt during acceleration and turning!

 

Some 75w-140 gear oils don't require the addition of a friction modifier. What brand are you thinking of using?

 

I was looking at using a cheap Wal-mart brand called Super Tech, 75w140 full synthetic because it cost $10/qt. Mobil 1 wanted $17/qt. I've been reading these forums and have heard that Royal Purple is the stuff to use. I decided to look online for Royal Purple to see where I can get it here in Jerkwater. I was shocked to find a place online that is selling the RP 75W140 for $9.99/qt!!!!

Going to buy it as soon as I get home (work firewall won't let me). Can you believe that deal? :-)

 

Yep! and with Royal Purple you don't need to add Friction Modifier!

 

Middle of project... fluid is out, pan is back on, but that fraking fill nut won't break free! I've been spraying it w/ WD-40 and using a 3/8" extension, but it feels like I'm going to strip the square nut out. Is there a secret or do I need a special tool for this? I thought a 3/8 extension is what everyone used...

 

bolt the cover back on add heat around the nut. Propane is fine just warm up around the nut not the nut. Now take a candle and rub / melt it on the threads let it cool down then use a breaker bar in the nut it should POP then turn. Or just use an air impact.

44dwarf

 

Whew! Found a torch and 2 hours later that sucker finally broke free. Why the frak would Ford put that nut in there so tight? Holy crap! I gave hit one last blow with the hammer and it barely moved! I kept at it and little by little it loosened up... wow! I was thinking this project was gonna take maybe an hour.... ended up being closer to 4. But... no leaks and saved myself some cash!

 

Let me tag on to your post since I am doing the same thing on a 1992, How long must the sealer (Red RTV) sit before I should refill with the Royal Purple?

Thanks!

 

For just this reason, I have heard it recomended more than once to make sure you can loosen the fill plug before you drain the old fluid. That way if you can't get the fill plug loose, you still have fluid in there and can drive the vehicle if necessary, while you consider your options. Same idea applies to transfer case and manual transmission fluid changes.

 

For just this reason, I have heard it recomended more than once to make sure you can loosen the fill plug before you drain the old fluid. That way if you can't get the fill plug loose, you still have fluid in there and can drive the vehicle if necessary, while you consider your options. Same idea applies to transfer case and manual transmission fluid changes.

 

I used Blue (don't know if it was wrong type) and waited 15 long minutes before reassembly. It worked great, no leaking and it's been driven for about 30 minutes after sitting overnight and most of the day.

Just make sure you heed the advice... loosen the plug BEFORE you drain! If only I would learn!