Trans./transfer case recommended fluid

Can anyone out there recommend the best oil to use for my t14 and Dana 18? I just finished disassembling, inspecting, an reassembling my t14 and my Dana 18 transfer case and i am asking for advise as to what is the best gear oil to use.

 

I just did mine and i used 80 90 wt

 

80-90 gear lube.

 

What are the thoughts about using synthetic? Any pros/cons?

 

I tried, and the word here is Tried, Amsoil 75-90 in mine. Worked well except for the D18 shifter rail seals, which would seep, even after they were replaced. No problem with the front and rear transfer case seals, but all were also new. Function wise, it did not appear to be any different than standard gear lube. I went back to 80-90 gear lube and the seep went away. Still running the amsoil in the diffs.

 

There are as many opinions as Chevy vs. Ford vs. Dodge

Personally I've seen too many leaks on older vehicles using synthetic and its cost shies me away. If a vehicle calls for synthetic then it should be used but if it calls for regular gear oil then that's what should be used imho. I've also seen transmissions not shift right because of synthetic being used where dino oil was called for.

 

yea stick with the regular stuff. Its gone this long without synthetic why not keep a good thing going