My first diff fluid change on the X. I don't have a lot of local choices and no local ford dealer (we're talking hours away). So this is what the only autoparts store in town had. Did i get the right stuff? The guy at the counter did the looking up on his system and came up with three 1QT bottles of 75W-140 synpower oil and a large tube of additive. instructions on tube say to use whole tube, no other instructions, no how many QTs it's good for...nothing.

The plan is to do a rear diff fluid change this weekend with all this stuff. (i forgot the Sealant so going back for that today) and if i need anything else or more of anything It'd be super to find out before i find out halfway through the change.



I don't have a service manual (i know i need to get one soon) yet so I'm hoping this all works out. Does anyone know what torque the rear diff cover bolts are done to? A utube video i watched said to apply sealant, let glaze, then attach cover (but not torque), then torque 30min later. That sound about right? Also they suggested to clean out the diff in brake cleaner? that sounds dangerous to me. I don't like the idea of using brake cleaner on anything i can't completely clean out (don't want any residue mixing with the oil). I was just gonna clean off the faying surfaces with alcohol to degrease and let dry before re-attaching the cover.

Any other hints, tips, suggestions or advice appreciated. I hate doing work on a vehicle without the factory service manual which i usually follow to a T...

 

When I first got my truck with 160k miles. I had Jiffy Lube change the front and rear diff fluids. I was told that I didn't need the Ford additive. Because the stuff they used already had the additives. Long story short, my rear end moaned when ever I turned a corner. I went to the stealership and purchased the friction modifier. My rear no longer moans. Use what you have, if it moans order the stuff from Ford.

 

Are you sure it is a limited slip"? , if so just use a quarter of that tube at a time and none at first. It has to chatter first and then you use it. Test it first for chatter before adding ANY. Maybe you can return it.

No need to torque cover bolts, the main thing is don't over tighten.

The oil you got is fine.

Any of the oil soluble cleaners are fine and not near enough left to contaminate anything, and that includes brake cleaner, gas, diesel, paint thinner, carb cleaner, solvent, alcohol, etc etc. Use any of it anywhere in there or on there, and just wipe it off or out.

 

Go to the Excursion Tech folder. Scroll down to the "Suspension, Steering, Axles, Hubs, Driveline, Etc" section and click on the "Rear Diff: How to replace pinion bearings and carrier/side bearings in 10.5 inch rear differential" link.

When that thread opens, scroll down to the bottom of post #8.

Stewart

 

So is there a negative to using the whole bottle? I don't really care about the cost of the tube (honestly don't know how much it was) but want to make sure i use whatever will avoid possible future issues. I was told that the diff fluid was black and dirty a while back and am finally getting to it now, so i'm sure it's well overdue for a service.

I THINK i have a limited slip. I posted a thread up earlier today to get some advice on decoding the tag on the diff (more geared towards what gears but applicable, but no responses yet.
https://www.ford-trucks.com/forums/1...-diff-tag.html

 

Cool, Thanks for the link. It says the oil he used had the modifier in it. I did a search and looks like this one does too, but guys say they still needed to use a small tube of additive to remove all chattering. I could care less about noise level but want to make sure if i'm doing this fluid change, i do it right (component lifespan wise).

 

You don't really need to know but don't put any in at first, then test for chatter. The code should be on your tag and door sticker but I don't remember what it is. Go to a gravel road and hit the gas, then check the marks. If it was someone that sells oil changes they could have lied. Ford doesn't recommend a change before 150k miles. Mine is original at 170k and looks and smells fine. The price is not a deciding factor with me either but you can safely put mod oil in a standard diff. (same as pouring it on the ground).

 

Tag seems to suggest 4.30 gears and limited slip per the link above, though i'm still waiting for a second opinion.

My truck had over 180K miles when i got it but it was probably not maintained well and I've only begun to go through things. It also had a brake controller installed. So with 4.30 gears and a brake controller i'm guessing the original owner probably got it for serious towing...

 

Test for chatter first! You can put too much modifier in a LS rear end and ruin it's effect.

 

No need to click that link and look at the side of the bottle to see if it has modifier. Also, look at the Valvoline website.

 

Yup seems that it does have it in it. So run without any extra and listen for chatter....check. Will do.

on a similar topic is 3qts enough? the guy at napa said yes but that diff link stewart posted said 3.5qts so now looks like i'm .5 quart short....

 

The manual says 6.9 pints (almost 3.5 quarts) so you might make it with 3 with the oil film in there already. I would fill it first with what you have. You can always top it off with non-synth (they are compatible) and non was used for 100 years already. Some people are filling those rear ends from the top breather hole, let us know if you do that.

 

Or filled it up to the side port until the fluid spilled out, let it seep out until stop then put the plug back. More than 3 qts fore sure, but I don't think when I did mine it took all 3.5 Qts

 

side port is supposed to be used.
The bottles say for limited slip, that usually means it has the modifier in it already.

 

So what's wrong with the top one?