Engine/Transmission (1998.5 - 2002) 5th Gear Nut Fix on A 2001 ?

[CrewCabDiesel]

I am pulling my NV4500 to replace and update the clutch, Does anyone know if a 2001 NV4500 5 speed has the 5th gear nut fixed ? Build date on the truck is 01/00. If not how hard is it to do the 5th gear nut fix, I have a 300lb touque wrench ? Also what other things should I look out for when the trans is out ?

Kyle

 

[FCrawford]

See ad on page 19 TDR issue 37 Aug/Oct 2002. Call 888 236 4800 and ask for Monty. They have the kit to correct the 5th gear nut problem and can tell you if yours needs the fix.

 

[TPlasek]

I think there is a general misconception of what causes the 5th gear failure in the NV4500. It seems lots of people think that the problem is in the design of the nut and if they use a different design that the problem is fixed.



Unfortunately the nut coming off is not the problem itself, but more of a symptom or result due the problem. The actual problem lies in the main shaft that goes all the way through the transmission. The fifth gear resides on the end of this shaft on a splinned section, and held on the splines with the famous nut. The problem is the length of the splines on the stock shaft are not long enough to fully engage the splines on the fifth gear. Over time, the small contact area causes the splines to deform. When this happens, the fith gear itself will rotate back and forth every time you go from a condition of being under throttle to a condition of letting off the throttle. The gear continues to rotate back and forth until it walks the nut all the way off the shaft and the gear fall off(so to speak). No matter what nut you put on there, the same result will happen because the problem was never fixed to begin with.



I have upgraded to the fully splined shaft to solve the problem once and for all. I still have to old shaft, 5th gear, and the old nut in the garage. I can take pictures if anyone is interested.



If you don’t want to spend the money on a fully splined shaft, then the only way you can buy yourself some more time is to change the nut AND the fifth gear at the same time. Piers sell them for around $40. This will only prolong the inevitable though…

 

[FCrawford]

The kit I referred to is the fully splined shaft which is manufactured by Bluementhals. You are correct on the fix.

 

[John Berger]

Post some pictures if you can. TIA



John

 

[Roger rodbolt]

Originally posted by CrewCabDiesel

I am pulling my NV4500 to replace and update the clutch, Does anyone know if a 2001 NV4500 5 speed has the 5th gear nut fixed ? Build date on the truck is 01/00. If not how hard is it to do the 5th gear nut fix, I have a 300lb touque wrench ? Also what other things should I look out for when the trans is out ?

Kyle

Kyle,

TPlasek's post is right on concerning the 5th gear defect. You have the option of waiting until you have a problem (I have had the original fail, the factory fix fail and used the Blumenthaul shaft) or fix the shaft now-Blumenthaul. If money is available you might want to buy a 1 3/8" splined clutch and convert your input shaft to the HD 6speed size shaft. I finally just dumped my 5 speed for a 6 speed and like the gear spread much better. To be fair, though, the 5 speed shifts easier and with the two shaft "fixes" is probably as strong. Larry