What is the correct or recommended lubrication oil for my Getrag manual transmission in my 1991 ram 2500 diesel pickup? The owners manual says Motor Oil, but I'm not sure I trust that. Help Please!

 

I looked under Amsoil and they recommend 5w-30 motor oil too. I'd say it's 5w30 motor oil. I would use Quaker State Full Synthetic 5w-30, it has the highest rated wear protection of any 5w30, upwards of 133000 PSI.

 

Thanks Kuvasz101. I've been doing a deep dive into this and came to the same results as your reply. It's hard for me to believe you would put motor oil in a hard working gear box. Everyone is saying to use Mobil 1 5w-30 synthetic motor oil and to use 5 quarts.
Thanks again,
Mike

 

My wheelhorse D series which is the heavy duty one called for motor oil 30wt in the hydrostatic drive. There was a tech article out years back about using 50% motor oil in the Chrysler automatic transmissions. It made a firmer shift. I used it in mine for a while then eventually changed it out without any issues. I'm sure you'll be ok with the Mobil1 5w30 synthetic but it has less wear capabilities than the Quaker State Full synthetic 5w30. Just saying. A great blog on oils is written by an engineer that goes by 540RAT. He tested upwards of 300 oils. He's the real deal. Check him out.

 

why not use synthetic ATF? It is sold everywhere, it’s what the new vehicles come with and have been for years…

 

Mobil1 ATF Multi Vehicle (synthetic) MUST BE MOBIL "1" NOT SAY JUST MOBIL has a fantastic wear rating over 125000 PSI.
Chrysler used ATF in their manual 3 speed with Over Drive transmissions in the Aspens and Volares during the 70s.

Here's a short list of very poor performing ATF fluids with zero wear protection tested by engineer and blogger 540RAT. Valvoline MAXLife, Multi-Vehicle ATF, synthetic, for High Mileage Vehicles, red bottle = 0 psi. Yes, 0 psi, that is NOT a typo. Its actual viscosity/thickness is even thinner than 0W16 motor oil. See the CONCLUSION section just below for the details on this ATF’s complete FAILURE.

• Ford Motorcraft Mercon LV ATF = 0 psi. Yes, 0 psi “ALSO”, that is NOT a typo. Its actual viscosity/thickness is even thinner than 0W16 motor oil. See the CONCLUSION section just below for the details on this ATF’s complete FAILURE.

• Castrol Transmax, Dexron-VI, Mercon LV, Synthetic ATF = 0 psi. Yes, 0 psi, that is NOT a typo. Its actual viscosity/thickness is even thinner than 0W16 motor oil. See the CONCLUSION section just below for the details on this ATF’s complete FAILURE.

• Mobil (NOT Mobil 1) Multi-Vehicle ATF, synthetic, blue bottle = 0 psi. Yes, 0 psi, that is NOT a typo. Its actual viscosity/thickness is even thinner than 0W16 motor oil. See the CONCLUSION section just below for the details on this ATF’s complete FAILURE.

 

540RAT dose excellent research. I value his opinion.. And do disagree on some of his research at times...But it is Darn Good Stuff....

But, I would stick with the MFG. Recommended Lubricant for your "Get-Rag" And service it as recommended..
After a rebuild, Then check with the rebuilder and see about what fluid to use....
Just my 2 cents... Cheers