REAR end FLuid replace

[Pontisteve]

Why synthetic fluid?
Is there a legitimate reason or do the Ford bean counters just want more beans?

I just did mine today, but did not use a synth and I dont really want to do it again

Well, Ford didnt use synthetic the first time, so I wouldn´t lose any sleep over it. But in a TSB, they say to upgrade to it. These guys have big engineering behind them. They don´t do things for nothing. I wouldn´t rechange your fluid, but next time I would switch up.

One thing worth remembering in this discussion is that the explorer IRS rear end is an aluminum housing. That might make it more prone to heat related problems, such as expansion. Synth fluid reduces friction, which reduces heat, which reduces expansion. Maybe they found a long term possible problem, in which synthetic fluid would have made the difference. Also remember that these vehicles are sold in 50 states. The climate and geography vary considerably, so just because it doesn´t seem necessary where you live doesn´t mean in death valley or the mountains that it isn´t a more sensative thing. But in short, it´s cheap to upgrade, and that oil is in the rear end for a long time. So you get your moneys worth for sure. Gas mileage might even be slightly improved, although a thicker fluid may counteract that benefit some too.

 

[Hitchhikingmike]

I just change out the oil in my rear end too. I used Amsoil 75W-140. Amsoil is the best you can put in your differential, plus I change the rear end oil every 20k miles to keep the rear end whine away. You would be surprised how quickly the rear end oil can darken after 20k miles.

The part where the Ford manual says that rear end oil is good for 100k miles, that is a huge joke.

 

[stuartr]

I was @ wal-mart tonight and noticed they have full syn. in their Super Tech store brand 75-140W. It is only $10.57 a bottle. Would this stuff be worth trying? I am just wondering if the premium price you pay for Mobil, Royal Purple and others is just a premium bottle or if there is really a difference. I may try it later. On my door sitcker it shows I have a "45" axle code. So according to a post on here I have a 3.55 comventional axle. So that means I don't need any added friction modifier right? Or should I still add it?

STU

 

[my pos mounty]

You do not need the friction modifier, since you do not have the limited slip differential or the associated clutch packs.

Walmart comment purposely withheld to avoid a rant.

 

[stuartr]

So I guess that is a no! on their stuff? I wonder who makes it for them?

STU

 

[backfrmcolorado]

hey anyone... i know this post is for newer x's but on the friction additive subject. on my 94 4x4 x i just replaced the rear end fliud after i replaced both seals. im not to sure with the whole 4x4 and axels things but with limited slip isnt just on wheel suppost to spin if i go around a corner. well if a punch it at a light and make a turn the whole ass end of the truck swings around and both tires are spinning. is that suppost to happen or in the past could someone have been lazy and not added the additive and could a screwed something up in the rear end.

any feed back would be helpfull... forgive me too if this is a dumb question, also have a wine around 45mph from rear end.

 

[my pos mounty]

So I guess that is a no! on their stuff? I wonder who makes it for them?

STU

I wonder the same thing, and to what spec.

I withheld comments that I have against the worlds largest seller of the American future and economy. I am in the minority in this country that refuses to buy so much as a pencil from them due to their corporate behavior. To each their own.

hey anyone... i know this post is for newer x's but on the friction additive subject. on my 94 4x4 x i just replaced the rear end fliud after i replaced both seals. im not to sure with the whole 4x4 and axels things but with limited slip isnt just on wheel suppost to spin if i go around a corner. well if a punch it at a light and make a turn the whole ass end of the truck swings around and both tires are spinning. is that suppost to happen or in the past could someone have been lazy and not added the additive and could a screwed something up in the rear end.

any feed back would be helpfull... forgive me too if this is a dumb question, also have a wine around 45mph from rear end.

Nope, actually the opposite. Limited Slip (when it works) engages both axles when spinning like that.

The whine around 45 may be a bearing issue within your differential.

 

[thepotroast]

I just wanted to add that there is also a big difference between Mobil1 and a product like Royal Purple or Lucas. Not only in dollas dollas, but also in overall effect.

I would steer clear of the WalMart 75w-140, stick with the name brands. Our rear diffs have a horrid reputation for whine and the need for a rebuilt early on, it's not really a diff to be screwing with cheap liquids.

The Mobil1 did absolutely nothing for my whiny diff, but I've seen many others here report they stuck some Royal or Lucas back there, and it quieted it down significantly. I am going to try this in a few weeks, have to mail order the Lucas or Royal because my parts store doesn't carry anything but the Mobil1.

 

[stuartr]

I guess I like wally world cause my wife works for them and they pay here rather well. So i live with them I guess. But sometimes they are a bully. But that is a competive market either bully or be bullied.

STU

 

[backfrmcolorado]

[/QUOTE]Nope, actually the opposite. Limited Slip (when it works) engages both axles when spinning like that.

The whine around 45 may be a bearing issue within your differential.[/QUOTE]


thanks a lot for the knowledge. just wondering cuz its time to get my tranny rebuilt again and while i was at it just needed to know if rear end needed rebuild as well. huess not, thanks a lot

 

[Pontisteve]

I changed the fluid to 75w140 mobil 1 syn in my 03 (non-posi). I really can't remember if it whined before or not because I wasn't paying attention. Obviously it didn't whine too bad, right?

Anyway, afterwards there was a slight whine if you cruised real evenly, where you were not accelerating or decelerating any. Its muted, but you can easily hear it if you're listening for it. I think it's just the way it is. Remember, we have an aluminum differential case, so my thinking is that you will probably hear some more whine than I am used to in my solid axle 8.8 Mustang rear end.

For the labor involved, I would use a name brand synthetic.

As for posi additive, just look up the axle code on your truck and see if it came with a posi. If it did, use additive. If not, don't.

 

[stuartr]

Here is the MSDS for the super tech stuff. Seems it is made by Warren Dist. I think that means it is a Quaker State product from what I can find.
http://msds.walmartstores.com/cache/339351.pdf
So not sure if I will try it or not.

STU

 

[Black Dynomite]

Planning on replacing the fluid in the rear diff shortly. fwiw my manual calls for a fluid change both front and rear, at 90000km (55900 miles)

 

[trump]

speed sensor plug

My 05 has rsc manual says remove fill plug 1 pint might run out. Refill to bottom of fill plug the add 1 pint in speed sensor plug . Where is speed sensor plug ? I can't find it. I looked all over diff

 

[XCAMP]

If you are talking rear diff, I have an 05 as well, just open it up, siphon out the old fluid, siphon in or shoot in new fluid plus diff additive sliplock if needed, till it runs out, pretty easy. Manuals are confusing at times, just look at it from a basic point of view. Won't get rid of the rear diff whine though, just so you know.

 

[jstorm001]

If you have a limited slip differential, you need modifier.

I read online somewhere if you use the synthetic oil you don't need the modifier because it's already in it is that true?

 

[turborich]

Some products claim that you don't need an additional friction modifier with their product. I would add it anyways, you won't hurt anything.

Even if you don't have a limited slip rear end you can still add friction modifier to an open differential if you have any whine. It may help to quiet it down and certainly won't hurt anything.

Only use 75-140 synthetic gear oil (friction modifier if required or experiencing whine) and that's it. (Mobile 1, Ford synthetic, Amsoil, Wal-Mart synthetic) don't let the price or brand fool you. Ford doesn't make their own oil and neither does Wal-Mart. It's all produced by a large petroleum company. The friction modifier can be purchased from Ford, Autozone, Pepboys, Napa, etc. It's widely available.

It's actually very simple, some folks just over complicate things and scare people away from this very easy job.

 

[Pontisteve]

That's about right. Ford switched everything to 75w140 synthetic. I use Mobil1 personally, but whatever synthetic you want is fine.

I would pop the cover off and drain the fluid. That way you can get all the gunk out, whereas sucking out the fluid doesn't really do that very well. I go the extra step in my cars and take a can of brakleen and hose the entire rear end guts with it until the can is empty. Let it all drain out, brakleen it, let it dry, and fill it back up.

I use gray silicone instead of a rear end cover gasket, as it doesn't leak over time if you do that right.

The speed sensor has wires going to it, and is installed towards the top half of the rear end housing in most vehicles. "Follow the wires" and you'll find it.

 

[aatomicdawg36]

I have a 2002 EXP, XLT - Axle Code 45- which is the Open 3.55. I have a leak in the rear axle pass (right) side and the same in the front pass (right) side. I've looked up part#. As near as I can tell, the rear should take the MOTORCRAFT BRS-40, but the FRONTS take either the BRS-10 or the BRS-31. Does anyone know what is the exact Part # for the front? Or how I can find out which part# my car takes ? THANKS!

 

[Pontisteve]

I find Rock Auto's catalog to be excellent for finding Motorcraft part numbers.