Syncros problem?

[scooper]

Ok, so I finally got my clutch problem sorted out, clutch works as it should now, I get engagement about halfway off the floor now, I can put in and out of the gears while sitting still with the engine running with no problem. 1,2,3 shifts are smooth, but going into 4th I get a small amount of grinding before it drops into gear. It seems to be more pronounced after driving a couple miles and everything is warmed up. Maybe a syncro?

[Wagon Master]

What are you using for transaxle lube?

[scooper]

Yeah, that's been a dilemma, I've tried to find oil that is rated GL-4, I couldn't find any, I currently have Lucas heavy duty gear oil in it, it has a GL4/GL5 rating, says it is safe for brass parts. It won't react with the brass. But maybe it is too "slippery" to allow the syncro to grip? I've thought about draining all the fluid out, flushing trans and diff with kerosene, and starting over with some fresh lube. The previous owner had been running Redline oil in it with a friction modifier to try to free up the posi clutches, ( another disaster I fixed), that could be contributing to the problem.

[azdave]

GL-4 oil? It might be too heavy for you but here in Phoenix I have had good luck with the stuff they sell at NAPA. Sta-Lube GL-4 85W90.
https://www.napaonline.com/en/p/SLRSL24239

[scooper]

I'll look for it, give it a try.