Engine/Transmission (1994 - 1998) Nv4500

[nfox]

Can someone explain to me what happends when you loose fifth gear in your transmission? Is the gear pressed onto the shaft by the nut? My friend has a 2001 with a nv4500 and had the update done last spring and didn't make year and 5th gear is out again. Where can he get the parts to get it fixed so it doesn't happen again?

 

[kentdiesel]

The reason fifth gear gives trouble in a NV4500 is because the mainshaft has half splines and half ground surface where 5th gear is located. Over time the gear starts to wobble and then pushes the retaining nut off the threads.



The aftermarket offers a fully splined mainshaft that supports 5th gear its entire width. A much improved setup.



Standard transmission offers a fully splined mainshaft, new 5th gear and updated retaining nut for about $300. 00



http://www.standardtransmission.com/



You will also need a mainshaft shim kit to set the mainshaft endplay.



Kent

 

[nfox]

Does anyone have a picture of the stock 5th gear shaft verses the fully splined shaft? Sounds like a person would be a fool not putting in a fully splined shaft when the stocker takes a dump.

 

[Dull Pain]

nfox - Go to www.quad4x4.com, look at their NV4500 pages. They have a pic posted that shows both half splined & full splined for comparison.

 

[nfox]

Thanks Dull Pain thats what i needed to see to convince me. Oo.

 

[bnelson]

4500 5th. gear nut

I believe it's more a matter of the vibration and harmonics particular to the Cummins diesel. The 5th gear nut un-screws, it is not pushed off. The word I got from Six States (a gear-train supply house, the Pasco, Wa. store) is that the transmission re-builders they deal with are stating that the fully-splined mainshaft will help, but there will always be a problem with the 5th gear nut backing off, especially if the truck is used for towing. What the re-builders are recommending as the best cure is to go back together with the best parts the owner can afford, and then tack weld the 5th gear nut to the mainshaft, in about two or three places. It isn't a matter of the threads on the mainshaft or in the nut stripping out, it just rattles loose. My first repair went 5,000 miles, the second 3,000 miles, and the cure with the "spark wrench" (welder) is still holding. For eventual dis-assembly at re-build time it's no problem to remove the welds with a cut-off wheel. Brad

 

[R C Cola]

5th Gear

On my 91 the Getrag died. When talking with the supplier of the rebuilt NV4500 w/kit I was assured that their rebuild would hold up to the hardest work loads. I tow heavy. They also assured me that it had all the latest upgrades that would keep the nut in place. That was April. In August (50,000) hard miles later I lost 5th gear in spite of all the improvements.

That gear is now tack welded in place because I have spoken to other drivers that have had the same experience I did with "New" transmissions, not rebuilt. I strongly agree with Brad on all points he has made.

Good Luck... . R C