Hi all Installing my 4 speed trans back into the car and like to change the trans oil. Most noted on all the GM boards not to use synthetic or GL rating of 5 or above for muncie trans. So know where to find the correct gear oil that is not synthetic and GL-4 rating. Thanks George
Do a search...there is some discussion about GL-4 versus GL-5 lubes for a Muncie. I use Amsoil 75w-90 Sythetic (GL-4) in my rebuilt Muncie. The bottle states that it is specifically designed for Muncie, Toploader, New Process, and other muscle car manual transmissions. I have used it for a number of years - shifts smooth and clean.
I prefer the old dinosaur oil. My local parts store got me some GL-4 however I had to buy it in a 5 gallon container. DO NOT USE THE oil that is GL-4/GL-5 rated!!! It is GL-5 oil. I have used synthetic in the past in 2 different transmissions. Both times I hurt the trans within 200 miles. I have to admit it was severe drag race duty. Each time I rebuilt the trans, I went back to the dinosaur oil and have had no problems. I did use original used GM parts. Maybe the new gears technology will handle the synthetics, I cannot say for sure. If you just drive normal daily use with no power shifts etc you will be ok. Myself I am sticking with the good ole dinosaur GL-4.
David What you wrote is what I read all over the internet. The only non synthetic GL-4 oil that I can find is produced by CRC/Stalube 85w90 GL-4 in a gallon container for $9.00. If you know a better manufactor please let me know. Thanks, George
This Spring I had my M20 professionally rebuilt by and very reputable performance shop. With everything I heard about gl4 vs gl5 I told them to give me the oil. I was given Napa brand GL4/GL5. When I asked about it I was told that its bull crap. Wondering if maybe the older parts theory has some merit.
The oil I have is Pensoil gear oil 85w90 and it is GL-4. My local store is not a chain in a small town and go out of their way to help the customer. Of course I 've known them for 30 years too. They called their distributor/supplier to see what was available. As I mentioned it is still available in 5 gallon only. CEN-PE-CO has it also. As long as it's not synthetic GL-4 go ahead and use it.
