Hey guys, I have a 94 Ram 2500 nv4500 360 4x4. I've had it for the last 25k miles. It's gotten harder to downshift from 2nd into 1st, in general, but especially when it's cold out. Also, when it's cold, it is hard to shift into 2nd until I've driven it for about 5 miles to warm up the transmission. 3rd gear has "grinded" on me once I think when I shifted really fast and it was cold, but it's only happened once. The 1st and 2nd problem though, isn't grinding. It's just "harder", if that makes sense. I had thought that it needed sincros, but I read somewhere that the system for bad syncros is grinding. If that's the case, than I don't think my syncros are bad, except maybe some wear on 3rd, which hasn't caused me any problems. What though would my 1st and 2nd problem be?
Thanks in advance, guys!
Courage

 

Check fluid level. Probably wouldn't hurt to just change it.

 

Ok, I'll do that. These transmissions take a special fluid, right? I've heard some say to use redline, and others ay to use Amsoil. Any "correct" answer?

 

Amsoil is probably fine. However watch videos from Andrew at Long Range Gear. He lives NV4500s every day and says he only warranties his units with Redline MT85. I got it relatively affordably through O'Reilly, although they had to order it in. I was a little concerned about fakes through Amazon or Ebay, although I don’t know if anyone is actually counterfeiting Redline.

If the problem persists, you need a rebuild. May not be the synchros per se but the sliders which engage them. The castle teeth get worn weird. Again, Andrew will highlight this in his vids at some point. Easily searched out on YT

If you undertake a rebuild, his Pt 1 vid is mandatory viewing. He covers everything you need from parts to tools to chemicals. Do NOT just order a $400 rebuild "kit" and think you're ready, because you're not. You need a lot more parts and a couple tools.

 

Ok, cool. I'll go with the Redline then.
I'm actually about halfway through that video rn. I'll finish it. Just got interrupted...
Really hoping i don't need a rebuiad!

One more question though. How hard is it to swap input shafts on the nv4500? I'm planning to swap in a 12v Cummins this winter, and it looks easy enough to swap to the bigger input shaft, but I've heard some people talk about needing to set up the preload, and others say you don't have to mess with it...

 

There's no preload, nor any adjustment on the input shaft. You could just change the input and be done with it, but correct way is to check and adjust the mainshaft play, which requires to pull top cover and rear housing, as the adjustment is at the rear of the main shaft. It's shown at the end of the second video from Long Range Gear.