NV4500 gear lube change suggestions

[GM Guy]

also has to be a full synthetic fairly heavy oil to tolerate the gear and bearing load. Synchromesh is good enough for the synchros, but the bearing and gear load is the other half of the needs of the NV4500, so the 12346190 (or redline or amsoil equivalent) is about the only one that can meet both.

 

[someotherguy]

Thanks for all the replies guys. After much reading on the subject I purchased the Amsoil recommendation. My understanding is that it’s got to be GL-4 and definitely not GL-5 to protect the synchros. Thanks again for the input.

The GL-4 vs. GL-5 isn't to protect the carbon-fiber synchros which are unique to the NV4500. Choosing GL-4 vs. GL-5 is to protect any "yellow metal" parts in the transmission; typically synchros in manual transmissions are bronze. The additives in the GL-5 spec gear lubes can damage bronze. Now this is an oversimplification and one should always check your specific application before choosing a gear lube: GL-4 is typically for transmissions, GL-5 is typically for differentials.

Richard