Is gear lubrication fluid different from ATF?

At one time gear oil was used for manual transmissions. In more recent years ATF has been used so the factory doesn't need to stock two fluids.

Gear lube is 80/90W gear oil for manual transmissions and differentials. ATF is for automatics.

Not so fast. ATF is also the specified fluid for a great many manual transmissions.

DS

"Recent years"...? No. I can think of manual transmissions for which ATF is the specified fluid going back to at least 1976.

And it's not so the factory doesn't need to stock two fluids. It's because ATF gives greater fuel economy (less gear drag) and allows the use of certain types of synchronizers that are not compatible with gear lube.

DS

I was refering to the last 15-20, (after all the torqueless wonder can use gear oil or ATF depending on the environment) but if makes you feel good to pick nits on two sentance post that gave the guy the basics of what he asked for rather than a complete detailed history of automotive lubrication, sure have at it.

Next time maybe I should just refer someone who asks a simple question to series of SAE paper numbers instead, that we can avoid these nit-picking opertunities in the future. Maybe it would be better not to help at all because it's obvious that I don't word my posts carefully enough to withstand the riggers of usenet nit picking when I don't think the thread is particularly worth that effort.

A nice arguementive manner to add more information. But it doesn't invalidate my statement.

If it isn't to not stock two fluids, why the didn't they just develop an all new special manual transmission lube that was dedicated to job or a lube not typically found in automobiles to get that .0001 mpg? (which of course wasn't an issue in 1976, a year with 500 cid V8s) Because that would have been monumentally stupid, when they could achive the goals using a fluid they already stocked and was widely available.

I highly doubt that it was some cosmic accident that ATF became the fluid of choice. ATF was undoubtly picked because it already existed and reduced the number of fluids that had to be stocked. Any engineer looking for a lube for his wiz-bang new sycronizer who didn't try to use / design for an existing fluid would be foolish if not worse. ATF would be the natural choice to go for.

Frick, even if it was a cosmic accident that ATF was the perfect lube for these trannies, the engineers' manager certainly took credit for it as a good thing.

Daniel J. Stern wrote in article >

I'll go you one better, Daniel.

When I was in Vocational School in 1963, our classroom instructor - Al Hoyle - owned a 1960 Plymouth convertible with a three-speed manual transmission.

Chrysler has just made the changeover to using ATF in their manual transmissions, and I was assigned the task to drain the gear oil out and replace it with ATF in Mr. Hoyle's car.

Chrysler's changeover had absolutely nothing to do with fuel mileage in the early '60s. Hell, muscle cars had not even crested the horizon at that time.

The changeover had more to do with ATF, being a much thinner fluid, being able to lubricate better than gear oil.

Once I got out of school, my dealership experience was primarily Chrysler, and as far as I know, Chrysler has used ATF in all manual transmissions since that time.

Bob Paulin - R.A.C.E. Chassis Analysis Services

AND transfer cases...

Rob

* * *

It depends on what types of gears are being "lubed" and what their application is.

ATF has lubricating properties, it does a great job of lubricating the planetary gears in automatic transmissions. It is also often used in rear-drive manual transmissions, and in some FWD transaxles and differentials. But if you were to use it in a rear-drive hypoid differential or a front drive transaxle with a hypoid differential (example: Chrysler LH cars with the 42LE transaxle) then gear failure WILL occur. It does not have the correct lubricating properties for hypoid gears due to the "brushing" contact that occurs between the teeth of hypoid gears. Thats why 80-wt, 90-wt, 80w90, 80w140, etc. grade hypoid gear oils exist in the first place.

Not true. ATF does not lubricate *HYPOID* gears sufficiently, for example, so it is not in general a "better" lubricant. Also, Chrysler used to include warnings that recommended converting transmissions from ATF over to gear oil for certain types of use and if "objectionable gear noise" was observed.

One thing it does do in a manual transmission is make shift feel consistent from full operating temperature all the way down to very cold temperatures. Shifting an A-833 or Muncie filled with 90wt gear oil in sub-freezing weather is a bit like stirring a vat of molasses.

Ever try to fill a transmission without the drive shaft connected? Sure they could have special plugs, remove them at the assembly plant, then check that they didn't dump too much fluid on the floor and clean up the mess at the end of each day, or just fill it after it's in the vehicle. You're running the factory, which option do you pick?

That would more or less support that ATF was used over a special fluid because it was there and available easily.

Of course it's fully assembled, but would you fill it with fluid before puting it on the vehicle?

I've filled transmissions out of a car with no leaks before. Remember, not every transmission will leak just because the drive shafts aren't attached.

Chris

Most transmissions are not assembled at the plant that assembles the vehicle. Handling and shipping a filled trans doesn't make sense. As already noted, some transmission have a plug in drive shaft, and many transaxles have plug in half shafts; the chance of a mess with a pre-filled trans is great. I've seen footage of assembly plants and all the fluids were added at near or at the last station. I have not seen many assembly lines, so maybe it's done differently elswhere.

Chas Hurst

Which maker(s) tests transmissions before installing?

Chas Hurst

How much workers comp do they have to pay out for the workers that slip and fall because of the fluid that spilled out of the trans when it was put in? I don't care how fast you are, there's no way you're not spilling fluid removing the plugs and putting in the drive shaft(s). Then, someone further down the line has to top off the tranny.

putting them in the car empty means no mess, no workers comp from slip and fall, one filling station rather than two. 100% test is not done in real factories, it's too costly and too time consuming. All in all I can think of no reason to pre-fill a trans.

I made no such assumption. For instance, the MANUAL trans in my 1973 Ford, that's RWD, BTW, has no drain plug. It's drained by removing the DRIVE SHAFT.

Sounds like recipe for failed transmissions in the field. Last thing one wants is field failures.

Now you are switching the subject to engines.... Anyway 100% test of each component before it goes on the car is silly and not done. There is no sensible reason to do 100% test of transmissions. If the trans is so poor that 100% test is required, the problem is the design or the manufacturing process, not a lack of testing at the end of the line.

100% test is extremely costly. It's easier just to give the assembled product a test at the end and put the ones that failed aside for rework than to test everything along the way.

Some things just increase the chance of screwing up and become too difficult to deal with.

A little over a year ago I had the pinon seal on my mustang replaced. I was going to do this job myself at first, but the price the dealer wanted made not worth the struggle on jackstands and without the special tools. One of the special tools was a plug that kept the fluid in the trans when the drive shaft was removed.

You don't trust your dealers to do anything that vital. The manufacturer is on the hook for warantee costs, not the dealer. As far as filling in the factory, the filler is simply set to a specific volume and the worker on the line pulls the trigger. It's the only way to prevent stupidity errors on the line. Torque settings are done the same way, the equipment is set, and then the assembly workers don't need to know the torque setting.

If they are doing 100% test, then they are wasting money or covering for bad design or manufacturing process. Rutine testing of samples is fine, testing the final product is fine. Engines are complicated enough as to be considered a final product in and of themselves so I can see engines getting tested. Testing individual transmissions may be good for corporate politics and finger pointing, but serves no useful purpose if the design and manufacturing process are good.

Now this changes somewhat if the transmissions aren't built in house. Because then the supplier will consider the trans a finished product.

Time. Money.

Then why are you taking offense at my statement that 100% test of components is extremely costly and silly?

Fill it, spill some, check, top off

vs.

Fill

I dunno, but if an automaker is going to put cheaper piston rings in an engine to save 5 cents a car I doubt they'll want to pay for

3 steps instead of one in the manufacturing process as a whole.

I've actually wondered how they do (or at least "did" in the past) myself.

In the case of Chrysler Torquflite 727 and 904 transmissions (the transmission of choice in my little fleet of vintage iron), filling the transmission is a two-step process. An initial 6 quarts of fluid must be put in, and THEN the engine must be started before adding the remaining 3-4 quarts (depending on transmission, torque-convertor, and cooler size). If you try to pump in the full load of fluid WITHOUT starting the engine, much of it will wind up on the floor because it will come out the vent hole. The engine must be started to move several quarts of fluid from the tranny case into the torque convertor and cooler before the system can be topped off. Torque convertor (and number of front clutch plates, band thickness, and number of front clutch springs) were all a function of the vehicle/engine combination that the transmission was going in, so I would assume that they put complete tranny/torque convertor packages together at Kokomo, but I've never read for sure exactly how they did it. And since cars with a 440-4 went down the same assembly line as cars with a slant-6 or 318-2, it is not necessarily true that any two cars in succession even needed the same total load of transmission fluid.