This is my first 5 speed truck, and first NV4500. Its got 160,000 miles on it. Every time I shift from 2 to 3 it grinds and goes hard. If Rpm is around 2200 to 3200 it really grinds hard, these transmissions have any problems with. Sincronizers ( sorry if spelled wrong ) any help would be great. Also have a real heavy SB clutch

 

yeah the synchros go out, if you dont put in the right fluid it will start doing that. I think there are 3 different kinds of fluid that are approved for these trannys

 

i use castrol 80-90 gear oil in mine have 289,000 miles on her with alot of torque and no problems yet

 

Yes they are right ......change the oil and see how it works then.........I use Amsoil synthetic syncromesh and it works great

disclaimer...........I am not affiliated with Amsoil in any way

 

Does it seem to work better after the trans is warm?

What clutch? How many miles are on it? When we added the southbend con FE to my 97 I had some trouble going from 2nd to 3rd or maybe it was 1st to 2nd. Anyway after talking to SB for a while we decided to get the upgraded hydraulics and it helped it out a little.

 

had the same issue with mine after upgradeing clutches as well but after time it went away for me

 

Hey thanks fellas for the responses.my clutch is the con fe I believe big single disc. Prob about 15,000 miles on it . Ill have to change the fluid in it . Would a synthetic 50w work. I was a mechanic at a semi shop and I rebuilt a few transmissions and put clutches in and we used nothin but 50w synth.even in the spicer, eaton 6 plus 1. Would 80w90 be to heavy of an oil? It shifts kinda crappy when cold

 

80W90 oil is not recommended in the NV4500. The Castor Syntorq (not available in stores) is one of a few fluids acceptable in the NV. The syncros and bearing lube is pretty finite and needs proper viscosity and lubricity additives for the tranny to live.

I have about 187000 miles on mine and its starting to do the same thing. Mostly on upshifts to 3rd. If you think about it, 3rd shifts are probably the most used and the syncros take a beating. I wouldn't be surprised if mine is on the bench in the next 25000 miles for a refresh.

 

The NV4500 takes the Syntorq as mentioned above. This is a 75W-90 gear lube with GL-4 specs. You don't want a GL-5 which most gear lubes are. AMSOIL has one as does castrol.

 

Very likely, what has happened is that someone has put the wrong oil in. The synchros in the 5 speeds are Carbon fiber composite and are very susceptable to damage with the wrong fluid.

I would use nothing but the recommended Castrol Syntorque. A warning - it is expensive and you likely already have some damage. You can try changing the oil and putting the correct stuff in but there is guagrantee that it will fix the problems.