Which Transmission Fluid is best?

[MADMODDER]

Unless your rock crawling stock is the best. The stock covers provide the best oil flow.

If they provide the best flow, why is there a Ford Performance version?

Looking at the inside of the 2 (Ford Performance and stock) they look pretty similar. Except the Ford Performance once is aluminum, finned and has a fill and drain plug and a port for a temp sensor. I wont be use a sensor but I do like the aluminum and the fins. And it just looks better, imo.

I can see how the Fins would obstruct some flow but there arent any huge flat spots like with the ATS (or similar) designs.

Links to each below.

Ford Performance Mustang Finned Differential Cover; 8.8-Inch M-4033-KA (11-14 Mustang V6; 86-14 V8 Mustang, Excluding 99-04 Cobra) - Free Shipping

FREE SHIPPING! GT500 Original Equipment. This Ford Racing Finned Differential Cover is the same exact one found as original equipment on the 2013 Shelby GT500 w

www.americanmuscle.com

Replacement Differential Cover REPF543503 | CarParts.com

Lowest price guarantee on Replacement Differential Cover REPF543503 only on CarParts.com

www.carparts.com

 

[MADMODDER]

I read that I may need friction modifier for the diffs.

This is the fluid I'm looking at.

75W140NS GL-5 Gear Oil

Contains extreme pressure additives like our 75W140 GL-5 oil, but lacks friction modifiers to balance slipperiness

www.redlineoil.com

Making sure I understand this correctly. If my diffs are limited slip, I NEED friction modifier. If it's an open diff, I do NOT need it. Right?

For 4x4 reasons, isnt the front diff a limited slip? Or should I lift it and turn one wheel to check?

 

[Shran]

I think maybe it's transmission dealers and rebuilders who turned the M50D R1 R2 etc into M5R1 M5R2 etc

M5R1 is the Ranger version, M5R2 is the F150 trans. They are somewhat similar but not interchangeable. Keep in mind that there are various versions of each that are slightly different. M5OD is just a generic term that we use that differentiates it from an FM145, etc.

I read that I may need friction modifier for the diffs.

Making sure I understand this correctly. If my diffs are limited slip, I NEED friction modifier. If it's an open diff, I do NOT need it. Right?

Friction modifier makes the limited slip clutch pack slip more than it does with just straight oil. It is unnecessary for Torsen limited slips or open carriers but it won't hurt them.

The general consensus is that friction modifier also makes the clutch pack last longer. I haven't run it in my wheeling rig and probably won't... I want my limited slip to act more like a locker than an open diff, but those who put a lot of street miles on their trucks should probably use it.

For 4x4 reasons, isnt the front diff a limited slip? Or should I lift it and turn one wheel to check?

You do not have a limited slip in the front.

 

[Josh B]

Then why is what the rebuilders call a M5R1 called an M50D by Ford and by parts dealers?

 

[MADMODDER]

Ok, so I dont need a friction modifier?

 

[4x4junkie]

The transfercase uses Mercon III spec fluid, Ford's transfercase fluid is Mercon III for 3 times the money.
I've only heard of synthetic fluids causing problems for 2 things: T5 transmission syncros don't like synthetic fluid because it's too slippery for the blocker rings to grip properly and Auburn gear told me not to use synthetic gear oil with my Auburn Pro because it would make noise. Auburn limited slips shed metal particles into the fluid so the fluid needs to be changed regularly and the particles will eventually ruin the bearings. I bought a Yukon clutch type diff to replace the Auburn.

There is no such thing as Mercon III fluid (or if there was, it's very long obsolete). It's either "Mercon", or, "Mercon V" for our trucks (I think you're confusing it with Dexron III, GM's spec for the same fluid).


.

MADMODDER, you're looking waaaaaaaaaayyyyyy too deep into this and making it much more complicated than it needs to be...

Since you have a 2010 truck, the only thing you need to do for your transmission is look for ANY fluid that meets the Mercon V spec. It's available everywhere. Not hard to find.

For the transfer case, you're looking for a fluid that simply states: "Meets Dexron III/Mercon specifications", or, "For older Ford & GM cars/trucks requiring Dexron III/Mercon fluid" (ANY fluid labeled "Dex/Merc" will be that fluid). Something stating: "For manual transmissions that require ATF" is also acceptable. Or just buy the t-case fluid already.

Same thing for the differentials, you only need to find ANY fluid that meets Ford's M2C192A spec. Another way to find it is to simply look for the "GL-5" specification in a 75W-140 oil (the Redline oil you linked earlier, for example). That should be all the information you need to know.

Limited slip differentials were not available in any form on 2010 Rangers, so unless you've swapped something into it, no, you do not need friction modifier.

 

[19Walt93]

After 42 years in a Ford service department I can assure you that Mercon III existed until Ford lost the right to use the name and discontinued it a few years ago. When Mercon V was released we were told to never mix it with Mercon III, then Mercon III went away and it was not only OK to mix them but Mercon V became the replacement for everything but transfer cases.The current transfer case fluid is Mecon III at a much higher price with a different name.

 

[4x4junkie]

Ford didn't "lose" anything... Ford has complete control of licensing rights to the name "Mercon" (as does GM with "Dexron"). They own these trademarks. Ford licenses the name to other manufacturers (such as Castrol & Valvoline) to manufacture the fluid in the aftermarket. As I already mentioned in a previous post, Ford is who pulled the license for the "Mercon" name and is why all of the aftermarket Mercon oils are now labeled "Dex/Merc" or occasionally some other name (this occurred in 2007, BTW).

The fluid you are speaking of is "Mercon". It was never labeled "Mercon III" in any recent memory that I can recall (about 30 years now), so if it was ever called that, it is a very long obsolete term and calling it that just adds to the confusion.


Edit:
Some interesting reading here:

MERCON - Wikipedia

en.wikipedia.org

 

[19Walt93]

Our field service engineer told me they lost the rights to the name, he may have been pulling my leg. It was absolutely labelled Mercon III and I still have some on the shelf in my garage. I base this on my experience in a Ford dealer, regardless what Wikipedia says. I can take a photo of the bottle if you really want to see it.

 

[19Walt93]

I was wrong. The Motorcraft bottle says : mercon/dexron III with mercon and dexron listed one over the other with the "III" off to the side. When they went to that bottle from the old one that just said mercon we called it mercon III, as did our parts department and the Motorcraft supplier.

 

[Dirtman]

This thread is making my head hurt... it doesn't take 5 pages to decide what fluid to use!

 

[Josh B]

How best to get it into the filler hole will come along soon enough Dirtman, just be patient

 

[4x4junkie]

I was wrong. The Motorcraft bottle says : mercon/dexron III with mercon and dexron listed one over the other with the "III" off to the side. When they went to that bottle from the old one that just said mercon we called it mercon III, as did our parts department and the Motorcraft supplier.

No prob. It happens (you're not the first one to call it that, probably for the same reason). MADMODDER seemed distracted by all the terms being thrown about here, I didn't want him to go looking for one that didn't exist, and to (hopefully) keep things easier to understand.

As for getting the fluid into the hole... Flip truck over onto it's passenger side using forklift, then pour into hole 2.75 quarts? Flip truck back onto wheels. Passengerside sheetmetal might have a few wrinkles afterward, but it's all just cosmetic

 

[JohnnyO]

Now I'm a little confused.

Do I need to find Mercon, or "dex/merc" tranfercase fluid for my truck or do I need to just hit up my local Ford dealer for OEM stuff.

I'm big on changing fluids. Generally I use Mobil 1 ATF in my transfer case and the manual tranny in my son's Mustang. A while ago I tried Redline D4 in the Mustang after reading good reviews on it. The car did shift a little better. Had some left over so I put it in my transfer case. Last time I did the transfer case I saw Valvoline Synpower Transfer Case Fluid at Auto Zone, it was a little cheaper than Mobil 1 ATF so I used that. Never got a used oil analysis on any of them but I change it every 30,000 miles so it probably doesn't matter what I use. If you want a go-to just buy Mobil ATF and you can use it in your manual tranny, the transfer case, and the power steering. I keep a turkey baster in the garage specifically for sucking out the power steering pump once a year and I refill it with Mobil 1 ATF.

My Sport Trac has a drain plug on the rear so I change it myself every 30,000 miles with Mobil 1 75w-140. The front is like a Ranger and pretty much impossible to change yourself so I take it to the Valvoline Qwicky Lube every 50,000 miles and it gets 75w-90 synthetic.

 

[JohnnyO]

Ok, so I dont need a friction modifier?

Not in the front. You will need it in the rear if the rear has a limited-slip. Some gear lubes like Mobil 1 and I think Valvoline Synpower claim they have friction modifier in them already but it wouldn't hurt to add it anyway.