I'm about to get a vehicle with a manual transmission (TR6060) that calls for an ATF (Dex III) fill. I've never had a MT call for ATF before (although I think it's not that uncommon). I was curious as to why this was a thing and what drives the use of an ATF vs a dedicated MTF in the transmission? Is there any harm in using a MTF that meets the viscosity requirements?
Manual Transmission Calling for ATF. Why?
- Thread starter 00scrub
- Start date
It was done for assembly line simplicity, not because it was the ideal fluid.
Ed Peters, a retired Chrysler engineer made that claim publicly and it's on Youtube.
Don't know why, but this issue has been around for me since 1979 Chrysler 3 speed manual transmissions in a Volare (also Dexron based). Initially very skeptical but it worked out anyway at over 100K miles, so that's what it got with no regrets or concerns on my part.
Many many discussions on using MTF in "ATF MT's" over the last 26 years. @MolaKule is awesome on the subject
Can be a feel issue (driver subjective)
Some MT's shear fluids more than others (use synthetic fluids with the least viscosity modifiers)
People used to talk more about impact on "synchros" (wear? feel?)
People can get overly worked up about brass/copper corrosion ("synchros" again) - yes it is a thing with old sulfur based conventional differential oil but not modern/synthetic MT fluids.
I honestly think most of the MT fill can revolve around about ambient temperature and engine heat to the gear box and such. If you live in a HOT place and a platform that transfers mucho heat, higher vis MTF - say over 10cSt @ 100°C - might be better. A cooler place and no heat transfer an MTF or even ATF in the 7cSt and colder winter rating (5W?) might be better.
Can be a feel issue (driver subjective)
Some MT's shear fluids more than others (use synthetic fluids with the least viscosity modifiers)
People used to talk more about impact on "synchros" (wear? feel?)
People can get overly worked up about brass/copper corrosion ("synchros" again) - yes it is a thing with old sulfur based conventional differential oil but not modern/synthetic MT fluids.
I honestly think most of the MT fill can revolve around about ambient temperature and engine heat to the gear box and such. If you live in a HOT place and a platform that transfers mucho heat, higher vis MTF - say over 10cSt @ 100°C - might be better. A cooler place and no heat transfer an MTF or even ATF in the 7cSt and colder winter rating (5W?) might be better.
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I've noticed feel differences between different MTFs in other transmissions. I'm pretty sure that's due to visc at 40C and 100C differences more than anything.
I was curious if there was something in the ATF additive package/design that was specific to some MTs hardware.
Honda still says you can use 10w-30 in their transmissions as an emergency fill, but to refill with Honda MTF ASAP.
I was curious if there was something in the ATF additive package/design that was specific to some MTs hardware.
Honda still says you can use 10w-30 in their transmissions as an emergency fill, but to refill with Honda MTF ASAP.
Interesting. Do you have a link by chance? I'm surprised it's also specified for servicing as well.
SAE 250 will fix that!
Kestas
Staff member
I'm guessing ATF is used for two reasons. It lubricates, and it also allows for friction components (i.e., clutch plates, synchronizers) to work, thus maintaining a balance between lubrication and friction. It may also be specified to simplify stock on the dealer shelf.
There are no hypoid gear in most so the "protection" requirements arent very high
ATF is aprox. the correct viscosity, stays thin enough in winter.. and works.
IF you get an MTF of the correct viscosity and gl-4 that also should work.. may have exceptions for fringe cases.
such as Porsche and Subaru that have hypoid gears and shared sump arrangement.
ATF is aprox. the correct viscosity, stays thin enough in winter.. and works.
IF you get an MTF of the correct viscosity and gl-4 that also should work.. may have exceptions for fringe cases.
such as Porsche and Subaru that have hypoid gears and shared sump arrangement.
Some manual transmission have needle bearings that won't roll properly with thick lube and will wear out quickly with gear oil. Others have automatic transmission clutch material type sychros instead of brass so they need Dexron for proper engagement.
I've used and seen thicker oils with needle bearing transmissions with out issues (Porsche 997 GT3). I would be surprised if the needle bearings can't handle the thicker oils.
I have heard about the syncro material question. I read that this was an issue on older Tremecs.
Are you saying the syncro cones are made of AT clutch material? I have only seen the friction material deposited onto the surface of the blocker rings before.
I have heard about the syncro material question. I read that this was an issue on older Tremecs.
Are you saying the syncro cones are made of AT clutch material? I have only seen the friction material deposited onto the surface of the blocker rings before.
My work friend's 80s vintage Mustang 5.0 with 5MT called for ATF. Been this way for at least that long.
That's interesting because manuals are typically pre-filled at the transmission plant.
GM even got to the level where automatics were pre-filled at the transmission plant because the vehicle assembly plants consider fluid fills to be a process headache. The cooler fittings that threaded into the housing came with wax plugs to prevent spillage and melted upon startup. The transmission was "over-filled" to account for the fluid volume in the external cooler and lines.
The use of ATF in manual transmissions has been around a long time (picture is from my 1969 AMX FSM for example). My 2011 Shelby GT500 (also a 6060 like you are looking at) required ATF and the factory fill was Dexron III. This was a 500HP supercharged car. I replaced it with Redline D4 (an ATF) with no concerns or issues.
Can you use dedicated MTF fluids, yes, but stay on the light side. When I did my Shelby, Redline MT-LV was not available or I would have maybe used that but, again, I had no issue with D4. D4 even cleaned up the 1-2 grind that transmission was notorious for.
Many others have a shared sump, all Hyundai/Kia 7 speed dual clutch units are.
