Which Transmission Fluid is best?

[gw33gp]

I just had my MD-50 rebuilt at 243K miles. It was working well but I wanted to get it looked at so I could drive it on long trips with confidence. They said it was in good condition but did replaced all the bearings and seals while it was apart. They also replace the 5th gear and slider due to it being slightly worn. I ask for all the parts and could not see anything wrong with 5th gear. I did not argue because I asked them to replace anything not up to spec.

I have run RP Synchromax in my transmission since the first lube change at around 6K miles. It was shifting hard when cold and I wanted to try another lube to resolve that. The RP Synchromax did that and shifted better overall in my opinion. The condition of my transmission at 243K miles tells me RP is a good lube.

My Ford drivers hand book indicates 80W-90 gear lube are to be used in front and rear differentials. One exception is the rear differential with the Torsen limited slip. Ford states right on a differential tag to "use only 75W-140 synthetic oil" with the Torsen differential.

I always use synthetic lubes but that is just my preference. Regular petroleum lubes are fine but generally need to be changed more often. I use Mobile 1 ATF in my transfer case and it has done well for me. I took it apart, when I had the transmission rebuilt, to check things out. It was still in excellent condition at 243K miles. I do a lot of extensive off-road trips also. I just replaced the seals and the timing chain. The timing chain was still good but had stretched just a little. The chain is not expensive and now good for at least another 243K miles.

My Ford repair manual states 36 ft-lbs for the transmission drain plug. I imagine the fill plug is the same. I have never replaced either plug or seal ring. They still seal perfectly.

 

[MADMODDER]

Differential fluid, synthetic or dino based is going to be fine as long as it has the recommended visocity.

I read that synthetics could be bad because they're TOO fine.
Seemed more like a fancy way of saying "I dont trust new technology" to be but I believe he was a younger tech. So I wasn't sure.
Any credibility to that?

As a side note, Fortechmakuloko just came out with a video for general recommendations based on what he has seen as a Ford Tech. Take it or leave it at your will but I thought it was interesting.

I'll be sure to check I out. Thanks.

 

[MADMODDER]

Any synthetic fluid that meets the "Mercon" or "Mercon V" specification should be fine for your '10's t-case. I would think Royal Purple Synchromax (or the Redline equivalent, assuming there is one) would be fine also. The t-case has very little friction going on inside it while in 2WD, so unless you do a huge amount of high-speed 4WD driving, I don't think a synthetic in the t-case would offer much benefit.

Mine is used almost exclusively for 4WD trips & camping, yet I still use plain Dex/Merc in my t-case (the M5OD however gets RP Synchromax).

For the differentials, I do believe Ford specifies 75W140 synthetic for the rear diff, so if you got access to Redline fluids, there you go. For the front, regular 80W-90 oil is fine.

I hardly ever us 4x4. Maybe once or twice a year. Only when I need it. I wish my Ranger was 2x4 but I couldn't find it in 2x4. Oh well.
I just remembered that oil's specified for Euros have a specification code. Does Ford do have the same or similar system? Or do they only specify by weight?

 

[MADMODDER]

I wouldn't use Mercon V in a transfer case, Ford's "new" transfer case fluid is actually Mercon III spec fluid for stupid money. A major brand Mercon III equivalent will do the job cheaper.

Is it better or would I better better off with Redline?

 

[MADMODDER]

I just had my MD-50 rebuilt at 243K miles. It was working well but I wanted to get it looked at so I could drive it on long trips with confidence. They said it was in good condition but did replaced all the bearings and seals while it was apart. They also replace the 5th gear and slider due to it being slightly worn. I ask for all the parts and could not see anything wrong with 5th gear. I did not argue because I asked them to replace anything not up to spec.

I have run RP Synchromax in my transmission since the first lube change at around 6K miles. It was shifting hard when cold and I wanted to try another lube to resolve that. The RP Synchromax did that and shifted better overall in my opinion. The condition of my transmission at 243K miles tells me RP is a good lube.

My Ford drivers hand book indicates 80W-90 gear lube are to be used in front and rear differentials. One exception is the rear differential with the Torsen limited slip. Ford states right on a differential tag to "use only 75W-140 synthetic oil" with the Torsen differential.

I always use synthetic lubes but that is just my preference. Regular petroleum lubes are fine but generally need to be changed more often. I use Mobile 1 ATF in my transfer case and it has done well for me. I took it apart, when I had the transmission rebuilt, to check things out. It was still in excellent condition at 243K miles. I do a lot of extensive off-road trips also. I just replaced the seals and the timing chain. The timing chain was still good but had stretched just a little. The chain is not expensive and now good for at least another 243K miles.

My Ford repair manual states 36 ft-lbs for the transmission drain plug. I imagine the fill plug is the same. I have never replaced either plug or seal ring. They still seal perfectly.

How do I tell which diff I have?

Lots of good info there. Thanks

 

[Dirtman]

You have an 8.8. Either look on the tag bolted to one of the cover bolts and it will have an axle code which you can look up to see if it's a limited slip, some have (LS) stamped right on them. Or just jack up the diff so both tires are off the ground and spin one tire. If the other tire spins the same direction you have a limited slip, if the other tire spins the opposite direction you have an open diff.

Ford specs using 75w140 in everything now (front, rear, open, or limited slip). I think they did this because it's cheaper for their dealers to just stock one fluid for everything. But if you have a limited slip you can use 80w90 as long as you add friction modifier or use 75w90 or 75w140 (both are synthetic) and will have the friction modifier already added.

I personally don't believe in using 140 unless you live in the dessert or tow a 40,000 pound trailer. I use 75w90 in everything. Change it every decade or 100k. For me a decade is sooner than 100k...

 

[MADMODDER]

@Dirtman, I literally JUST watch a video about doing rear diff service by, I believe "ChrisFix", he mentioned the tag on one of the diff bolts.

I know about lifting the drive wheels off the ground and spinning them. Idk why I didn't think to apply it to this. I'm kinda retarded.

I live in the south. Humidity is a major factor. The rate of heat exchange is similar, if not worse, than being in a dry desert. You think it's worth running the 140 in my case? I dont tow regularly.

 

[Dirtman]

Either will work fine in my humble opinion. If they are the same price, get 140 if it gives you peace of mind. I have trouble finding it in stores around here which is why I just use 90. You wont see any advantage or disadvantage using either fluid in a ranger. A race car, or a f350 dually towing loads... then there's some argument to use 140. But it's a little tiny pickup truck lol. 80w90 dino oil was spec for that rear for decades and it's still the same differential it was back then... (I think the 8.8 came out in the late 60's? 75w140 didn't exist back then and they worked fine)

 

[4x4junkie]

I just remembered that oil's specified for Euros have a specification code. Does Ford do have the same or similar system? Or do they only specify by weight?

Ford has codes also.

80W-90 gear oil = M2C197-A (dinosaur oil)
75W-140 gear oil = M2C192-A (synthetic oil)
80W-85 gear oil = M2C83-C (dinosaur oil, for Mitsubishi manual transmission)
I also see in some of my older manuals reference codes for other axle lubricants: M2C154-A, M2C105-A, M2C108-A, though it doesn't give details about the fluid other than to call it "Hypoid gear lubricant", "Rear axle lubricant", etc.

For ATF, the names "Mercon", "Mercon V", etc. are the actual "codes". The only ATF relevant to RBVs with an alpha-numeric code is "Type-F" fluid (M2C33-F) used for the early non-OD automatics, and for the power steering thru 1995.

Infact, every fluid & lubricant Ford uses seems to have a code (M17P5-A, M8B16-A2 are two codes I found for windshield washer fluid)

 

[Josh B]

Anyone know the code for chowda? Actually I only go by the weights anyway, as well as the brands, so far I've used mostly Motorcraft for all of it, engine, trans, TC, and thankfully I have an original CD Ford Manual for my year model (the same one used in their dealer repair shops in those years which basically covers it all very comprehensibly, mechanics, emmission, and electrical), which I have used extensively in repairs and information

 

[Dirtman]

Its "chowdah"!

 

[19Walt93]

I'd use 75w140 in the rear end, it's not too thick. The viscosity doesn't change from 75 to 140, when cold it's no thicker that a 75 weight and when hot it's no thinner than a 140. "Multigrade" fluids are misnamed, they're just affected a lot less by temperature change. In NH wew get sub zero weather every winter and I've never had a problem with 75w140.I suspect Ford used 80-90 in the front end because they knew most people wouldn't be in 4x4 and stressing the front end very much and 80-90 is cheaper.

 

[sgtsandman]

I read that synthetics could be bad because they're TOO fine.
Seemed more like a fancy way of saying "I dont trust new technology" to be but I believe he was a younger tech. So I wasn't sure.
Any credibility to that?

Ford has been using synthetic oil or synthetic blends for some time. So, they shouldn’t be a problem.

Synthetics tend to keep things cleaner and they hold up better.

That being said, there is absolutely nothing wrong with using petroleum based oils as long as one follows the recommended service intervals. They have been tested to work just fine.

Me, I use synthetics but don’t go top of the line. I buy whatever is on sale with a decent filter (if applicable). Top of the line stuff definitely keep things cleaner than the bottom shelf but the bottom shelf keeps things cleaner than dino lube. It all depends on how much you are willing to spend. Since I have three vehicles to take care of, I gotta balance the hit the wallet some. When i just had one, top shelf was how I ran.

 

[gw33gp]

I read that synthetics could be bad because they're TOO fine.
Seemed more like a fancy way of saying "I dont trust new technology" to be but I believe he was a younger tech. So I wasn't sure.
Any credibility to that?.

I am a chemist. I don't specialize in the petroleum industry but I can tell you "fine" is not a term used in relationship to oil. Fine is a term more related to solids like powder. Viscosity, polymerization (short chain to long chain), branched, chemical modification and so on are some of the terms used. Synthetics are much more refined and controlled than standard grade petroleum oils. There are many ways to make synthetic oil, but the end result is they are tailored to perform better than standard grade oil in most aspects. Operating in temperature extremes (low and high) is one of the benefits of synthetic oil. There are many other benefits also and very few negatives.

I know the are many stories about synthetics leaking through seals, but I have never experienced leaking with synthetics any more standard grade oil does. Synthetic tend to clean better and I suspect people that experienced leaking when using synthetic had used standard grade oil for a long time and the seals or gaskets had gummed up enough to minimized leakage. When they switched to synthetic, it began to clean up the sludge and found a path to leak. The polymer chains in standard grade petroleum vary a lot in chain size and branching because it is refined from crude oil. Synthetics are built from base stocks to produce a more uniform polymer with less variation in chain size and branching. Shorter chain size polymers should have more tendency to leak than longer chain and tend to be more volatile. Standard grade polymers have a percentage of these short chain polymers and most synthetics do not.

So, I find no credibility in; "synthetics could be bad because they are too fine". It is an opinion that is not based on fact

 

[Dirtman]

Synthetic or conventional both are graded by viscosity. A 90 weight conventional is the same viscosity as a 90 weight synthetic. Kinda like which weighs more, a ton of bricks or a ton of feathers...

I've never heard of or can think of a scenario where there would be a reason to advise against using synthetic oil. One minor exception might be on an old leaky neglected engine. Synthetic won't hurt but is probably gonna make it leak worse.