Engine/Transmission (1998.5 - 2002) 5th gear nut nv4500

[134x4ctd]

My friend has a 1999 2500 4x4 with an NV4500 trans. He is replacing his clutch with a south bend and he asked me if he should do some kind of fix for the 5th gear nut problem. I have not owned an NV4500 for about five years so I am not sure what the best preventive fix is for this. Any thoughts?

 

[steved]

If he has it out, there is an updated nut from Dodge that is supposed to help prevent it.

There are other options, but requires a partial teardown (IIRC) of the trans to replace the shaft.

 

[KNetherby]

My neighbors 98. 5 they use to haul a trailer all over US had this nut back off 3 times, once stock config and twice more with the upgraded nut fix from Dodge. This last time the mech tak-welded the nut on to the shaft. Sounds pretty extreme but they didn't want to tear down the transmission for the upgraded shaft. I wouldn't recomend it lightly but then you know these things rarely brake down in the driveway.

 

[Joseph Donnelly]

The problem was discussed in some detail way back in Issues 30 (p. 36) and 31 (p. 23). Basically, New Venture produced the mainshaft with loose-fit splines only part way under the fifth gear on the mainshaft. The rest of the gear, including the end of it with the teeth, rests on a smooth surface. The gear is splined inside, so the splines of the gear hammer into the shaft from the engine torque and vibration. Once the shaft is indented, the gear can “rock” and no nut will hold it from “wiggling. ” It will kick off the nut, and slide out of place, hence no fifth gear any more. Welding destroys the heat treat of the gear and shaft in the area of the weld, and cracking is common down the road. In extreme cases, the shaft can break. The only proper fix is a new, aftermarket fully-splined main shaft with snug-fit splines, and a new nut. Standard Transmission and Gear (Standard Transmission & Gear or 800-std-tran) and others offer the parts as a kit. You can buy just a new nut from them or from Dodge and inspect the mainshaft on that truck, but it will probably be indented and will fail some time in the future. If you do replace the shaft, get the small parts kit including new snap rings along with the shaft kit.