I know this is more of an engineering question that most people won’t know the answer to but as the title suggests how do manufacturers go about selecting the oil weight they recommend for their manual transmissions? You have gear oil as thin as 75w all the way up to 75w90, and some even using ATF.
Why does one manufacturer go with 75w and the other 75w90. What makes 75w90 the fluid of choice in say a Toyota transmission, but not a 75w or a 75w80 fluid? And will using 75w really be that detrimental?
Naturally my intuition told me well of course your compact cars use light weight fluids as they don’t see the stresses of a SUV or truck on a daily basis, or tow for that matter. Where as your “heavy duty” truck transmissions need the juicy thick stuff. From my Isuzu days I remember Isuzu recommending 10w30 motor oil in their troopers that used the AR5, while the same transmission under dodge (AX15) used 75w90.
The Mercedes G56 manual transmission. Ram tells you to use ATF in their Cummins powered heavy towing truck where as Mercedes says to use 75w90.
Point is that there isn’t the rhyme or reason that I was expecting. What are your thoughts? I wanted to get other minds in on the subject and get other perspectives.
Why does one manufacturer go with 75w and the other 75w90. What makes 75w90 the fluid of choice in say a Toyota transmission, but not a 75w or a 75w80 fluid? And will using 75w really be that detrimental?
Naturally my intuition told me well of course your compact cars use light weight fluids as they don’t see the stresses of a SUV or truck on a daily basis, or tow for that matter. Where as your “heavy duty” truck transmissions need the juicy thick stuff. From my Isuzu days I remember Isuzu recommending 10w30 motor oil in their troopers that used the AR5, while the same transmission under dodge (AX15) used 75w90.
The Mercedes G56 manual transmission. Ram tells you to use ATF in their Cummins powered heavy towing truck where as Mercedes says to use 75w90.
Point is that there isn’t the rhyme or reason that I was expecting. What are your thoughts? I wanted to get other minds in on the subject and get other perspectives.