Engine/Transmission (1994 - 1998) NV4500 problem

[froghunter]

My 1998 2wd 3500 5 speed manual transmission has begun to slip out of fifth gear into neutral on down hill travel. Initially it only happened with the exhaust brake engaged, but now it has decided to do it without the exhaust brake too. When it happens, I have to put it back in gear and manually hold the shifter to keep it in gear. The truck is dedicated as a tow rig, pulling a 24foot trailer. The previous owner had the transmission worked on and put in a splined shaft to fix a lost fifth gear. Has anyone experienced this, and what is the remedy?

 

[gary johnson]

here's my 2 cents worth frog..... I have a '98 4x4 with the same... . nv4500. Great trannny..... 5th gear went south on me at 131,000 miles and from my research, found a shop in Memphis,,,,High Gear transmission and Steve actually explains what happens. The splines only go halfway thru the 5th gear and constant lugging will knock it off the shaft. Your previous owner had the upgrade shaft put in, but no idea why you are losing it now. maybe shotty work at the shop. There is a 5th gear supernut available Google it... . at 131,000 I went for the reman transmission and new 13" clutch

 

[GAmes]

I had a NV4500 rebuilt and the first time I towed it started popping out of 5th with the EB on. 7000 miles later it cratered, 2000 miles from home. The rebuilder sent me another transmission and paid for the R&R, but I lost 4 or 5 days of work.



I don't know what is causing your problem, but something is broken and now is the time to get it repaired.

 

[SRadke]

The detents that hold it in gear are not associated with the fully splined shaft and/or the 5th gear nut issue. They are also accessible from the back if you pull the tailhousing on a 2wd. You could have something as simple as a broken detent spring. Tough to tell without going in there.

-Scott

 

[Joseph Donnelly]

Pull the tailhousing and check the synchronizer assembly that is attached to the fifth gear on the countershaft. You can remove the assembly by taking off the snap ring retainer on the end of the countershaft.

 

[Nyoest]

My fifth gear syncro let loose with a bang.



As stated pull your tail housing and inspect. Should look like the first pic.



2nd pic, Look closely at the gap between the c clip gap. There is no teeth left on the interior.

 

[froghunter]

Nv 4500 problem

Thanks everyone for the input on my problem. I shared your thoughts with the local transmission guru, and he agreed with your comments. Am scheduled soon for a R&R and fix of the problem NV4500.



Mike

 

[JKosten]

While you are in there get the upgraded main shaft kit. It will add to the longevity of the repair.

If you really wan to spend some money get the Street Dual Disk kit from Southbend and a 1. 375 input shaft. It will handle more power and torque. The trick part it is does not feel like a DD when you step on the clutch.