I put a reman NV4500 in about 3 years ago. It started popping out 5th when letting off, so I removed the tail housing to see what broke. The countershaft 5th gear had alot of play, and the countershaft is grooved really bad where the bearing was sitting. So I need at least a new countershaft. But here's my question: I really need to use the truck before I'll be able to rebuild the transmission. So can I put it back together without the countershaft 5th gear, synchronizer assembly, and shift fork and just run it as a 4 speed for a while? I'm going to measure the end play in the main and countershafts, but they seem ok at first glance.

It should work just remember that 5th gear is MISSING. I totally get what you are saying just don't need the bad bearing and gear banging around. Yes it should work just be aware.

Edited May 24May 24 by Mopar1973Man

Do you know what would happen if you try to shift into the now-missing 5th? Could anything bad happen?

Should not do anything per se being the gear is missing. It should be like a second neutral.

I would suggest changing to 50 SAE Transmission fluid. Much thicker lube and should stop the wear like that bearing. I was losing hard facing on the gears.

Does the 50 SAE fluid work with either brass and lined synchronizers? Do you have a preference when replacing them?

Yes sir I'm running brass syncros in my NV4500 and no problems to report even with subzero temperature in winter still shifts good. My problem was with higher HP I was eating the hardfacing off the gear teeth. 50 SAE transmission fluid stopped this problem. Typically sold as a GL-4 fluid synthetic.