manual trans fuild vs. differential fluid

[ppd1107]

I am working on a 78 Jeep CJ7 with a three speed manual transmission. The Hayes manual calls for a GL-4 lubricant in the transmission, and a GL-5 lubricant in the transfer case and differentials. I went to O'Reillys and they had a gallon jug of "Master Pro" gear oil. The label indicates that you can use the oil in Man transmissions, differentials and rear ends. It is a GL-5 but the label also indicates that it can be used in place of a GL-4 lubricant. I took the product at it's word, bought a gallon and have used it when I changed out the lubricant on the transmission, transfer case, and both differentials. Now reading this forum it is not clear whether I need to put a GL-4 only lubricant in the transmission or not? Can anyone make this a bit more clear cut?

 

[Kuato]

On a 1978 IMO, the GL5 that you used should give better service than the GL4 of the 70's.

That said, if your transmission shifts easily without any problems that's your answer that it's ok.

 

[expat]

Originally Posted By: Kuato
On a 1978 IMO, the GL5 that you used should give better service than the GL4 of the 70's.

That said, if your transmission shifts easily without any problems that's your answer that it's ok.


As I understand it, the issue is with Yellow metal components (syncro rings and thrust washers) being eroded due to the reduced amount of Acid Buffers in GL5.

 

[mechtech2]

I'd get a dedicated manual trans lube from Amsoil or Redline, in the proper viscosity.
It's all about the synchros - keeping them from corrosion and having proper friction engagement.
Other than that, the rest of the transmission can use regular gear oil just fine.
But really, you only change out the trans oil rarely, so get the best right now.