ATF has been used in manual transmissions and transfercases since the early 80's. it is obviously capable of lubricating gears, chains,needle bearings, roller bearings and wet clutches. It's my opinion ATF, aluminum cases and chain driven t-cases were brought about by the need for fuel economy. It's also my opinion that the older trucks lousy economy is attributed partially to heavy gear sets rolling in heavy oil. So, with the proven track record and flexibility of ATF, why couldn't it be used in place of 80-90w in vintage trucks? Like my 76 F250 4x4 with a NP435/205? And why not differentials? I'm really leaning towards giving it a go. I know we all have our opinions and reasoning. I'm hoping to grab the attention of a lubrication professional. So, why not?

 

If you change your mind on ATF, you could consider a full synthetic 80-90 gear oil or talk to a specialty lube company about lighter gear oil options such as a 50wt.

 

i really don't think you would want atf in a differential. gear oil is measured on a different scale then motor oil but i believe an 80w90 is similar in viscosity to a 40 wt engine oil at operating temperature.

an atf is like a 10 wt oil which is way too thin for a rear.

i think you would destroy a rear end quite quickly using atf instead of gear oil.

 

Engineers have very good reasons to specify the types of lubes to use in different equipment. Ford (or Spicer or Dana, etc.) spent millions of dollars designing, testing, and developing their products. You can convert to synthetic equivalents if you like, but you obviously don't understand oils or this question wouldn't have been asked. Unless you enjoy replacing components or have cash to burn, I'd strongly advise you not to try and reinvent the wheel.

 

In Ford tractors Tractor Hydraulic Fluid (which is very similar to ATF) is approved by Ford to replace 90 wt. EP gear oil in the transmissions and rear ends.

A tractor experiences a different set of conditions than an automobile or truck, but there are still bearings and gears (straight, spiral, and hyphoid) that experience similar loads related to rolling and sliding contact.

My point is that Ford examined the conditions in power train gearboxes and revised their recommendations in favor of lighter weight oil in at least one case. Researching Ford's recommendations for later, similar applications should indicate what modern lubricants will work well in older gear trains.

 

I'm not a petrol engineer but I do know some about lubrication. I do know ATF is not good in a hypod diff. Gear oil has pressure additives to keep the gears from wear. ATF cannot suspend those additives. Think of adding sugar to a drink. You can add so much til you have fallout. Not quite the same for oils but you get the point. Oils are formulated for different applications, wear situations, resistance to flow, thermal break down and so on. Some mecahical systems don't care what the lube is as long as it has some but others require specific lubrication.

 

Thanks for the replies. I knew this could be a controversial thought I had, and even bring my credibility into question! I was looking to see others thoughts and reasoning on this aside from the "don't be stupid! This oil goes in this hole, that oil goes in that hole!" type comments. Will I have ATF in my rear diff any time soon? No. I understand that different applications benefit from different additive packages. I do have a basic understanding of lubrication and the need of different grades and viscosity. I don't know enough to preach it just enough to spark questions, and ask... Why not?

 

Ya know what bothers me most about this OP's latest comment is this was all pretty much a waste of time. For those like myself who try to help or educate those without knowledge or experience fomenting "interesting" but contrived topics our time is better spent elsewhere.

As the post by VocaTexas so eloquently says specifications and products are usually simultaneously developed to provide maximum life, durability and reliability to the end user. The fact that some specifications change over the life of some components or systems shows there's on-going research and testing being done even on things already in widespread use.

I've never found anyone wasting my time---other than 5 year olds----as all that "interesting" or "thought provoking", not even a little.

 

Just a data point here, my E4WD Aerostar comes with ATF in the Dana 28 front differential/axle. It's a relatively small differential, and takes 33% of the drive power under "open" mode, and 50% under locked mode. The van is pretty heavy for a mini, at 4100 pounds unloaded, so I sometimes wonder whether that front diff isn't being overloaded.

Some of the guys on the Aerostar forum suggest replacing the ATF in the front diff with gear lube because they don't trust the ATF to protect the gears. I did that, and ended up with the lube expanding so much from heating that it pukes out of the vent tube after every drive longer than about 1/2 hour. I am slowly replacing it with ATF again, and hope the mix won't hurt it, as dropping the diff/axle is a bit of a chore.

I'd like to think that the engineers who designed the diff would know what they were doing, but I also know that they've made mistakes in the past.

 

"The fact that some specifications change over the life of some components or systems shows there's on-going research and testing being done even on things already in widespread use. " as stated by JWA in his post. This is exactly the point that pushed me to ask my original questions.

It is not my intent to waste anybody's time, the value of time is not lost to me. I appreciate all the valuable information available on these forums. I hope that in some way I have contributed to others, even if its only through the questions I have asked.

Unfortunately, one question that I asked, " what about diffs?" , wich was merely an afterthought, has skewed this conversation away from my intended purpose.

My original thought when starting this thread was, " is there an ATF that would be well suited for my NP435/205 gear boxes? one ? the other? or both."

Regardless of what I do or dont know, here is my thinking-

New Process 435 and 205 gear boxes are 1960's technology. They were spec'd for lube accordingly. Lubrication has came a long ways since then. in the last few decades ATF has replaced traditional gear oil in many of its traditional applications, including manual transmissions and transfer cases. It has also proven to perform well lubricating wet clutches, chain drives, power steering systems, helical gears, spur gears, planetary gears, and even HYPOID gears all in the automotive industry.

For those who are unsure, a hypoid gear is a spiral cut bevel gear set in wich the pinion gear intersects the ring gear below its centerline. It is your standard automotive differential.

So back to my original thought, " is there an ATF that would be well suited for my NP435/205 gear boxes? one ? the other? or both."

I dont know, this question has yet to be satisfied. I would like to think someone has factual enlightenment on this subject, and that even more find it as interesting as I do.

 

Some mfg's that specified ATF in gearboxes later released TSB's stating to discontinue ATF and use MTF/MTL lubes.
So I'm not sure the track record of ATF in gearboxes is as good as one might think.

 

The Borg-Warner T5 transmission that came with all the 5 liter Mustangs from about the mid-80's to their last production used ATF. I think a lot of the follow-on models from B-W also used ATF. I didn't see a lot of problems with them due to the lubricant used. The common problem was broken 3-4 shift forks due to over-enthusiastic shifting.