97 2500 stock. 5th gear just stopped working. No warning, no symptoms. Just quit. Anyone have a clue before I tear down?

 

The nut that holds 5th gear on backed off.
Pretty standard issue with higher mileage NV-4500s.
My old '95 I bought new, let go at about 225,xxx miles.

 

The NV4500 was a 4 speed that was converted to a 5 speed. The 5th gear is the added section on the back of the main housing body, and the 5th gear shaft is only supported by one bearing. Adding to their dumb design, they also didnt spline the whole shaft, so the gear only sits on about half the amount of spline material it should. This weakness will allow the 5th gear to rock back and forth under on/off throttle conditions, and is exacerbated even more when towing in 5th gear too. Over time the nut holding the gear cant hold the movement back and the nut backs off and the gear falls off the splines.
In respect to that, I never tow anything heavier than a row boat in 5th gear, and I'm very gentle with my throttle while in 5th gear. And...I never use my exhaust brake in 5th gear either.

Over the past 15 years or so I've read where members have tried any and all kinds of fixes but sadly nothing works for very long. Even the new aftermarket fully splinned shafts are not as strong simply because they come from hecho en China and their metallurgy is terrible.

But.....there is only one fix I've heard of which supposedly solves the problem once and for all. Disclaimer: I havent done any research in the past couple years to see if anyone with this fix has had to revisit it either but by far it has the best track record out there. NV4500 Transmission 5th Gear Repair

 

A lot of help. I contacted the people at Fifth Gear Fix. I couldn't find any negative comments and the fix seems reasonable.so I'm going to try it. I was told about welding, but that sounds a little drastic. I appreciate the fact that you went into a little detail about the trans. Thanks again.

John

 

Post back how it works for you...

 

Sorry, this is really late. People at 5th gear fix called me back. Really nice folks. their fix only works on 4wd. of course mine is 2wd. Long story short. Reinstalled 5th gear new nut and red lock-tite . Not a bad job. Alive in 5 for the time being. Thanks again for your help.

 

Maybe you could " steal the idea" for the 2WDs? The reasoning is sound, the method to keep the nut from turning is good, but the product is only for transmissions feeding a transfer case.

(Disclaimer- I never saw a 2WD with any manual trans over here so I do not know if it is feasible- about legality I suggest talking to your lawyer- i am not responsible for anything in this post)

 

Thanks for the advice. I also share your affinity for Bikes. 2 BMW's r-85 and r-100, Yamaha 1100, 125 James, 650 Megro., Pre unit 650 Triumph. I have pickled the Megro and James because of lack of parts.