My NV5600 has the dreaded 3rd gear grind. I have tried changing the fluid, and while it vastly improved the shift feel it didn't cure the 3rd gear problem. If i flick the shifter towards 4th and then into 3rd it goes everytime. If i double clutch it goes most of the time, so it could just be my double clutching skills after all im not a truck driver. If you place your hand on the shifter when in 2nd you can feel the stick wobbling. I am thinking there is a dead synchro on 3rd and a dead bearing in the rear of the case.

However my truck is a 2000 which i am told is the cut off year for the early/late input shafts and gears. So it could have either. I do not know the history of this transmission as i purchased the truck with 195k. I know there is an ID tag on the top of the bellhousing but since i don't have the transmission removed and don't want to until i get the parts to do the job i would like to find an alternative means of identifying whether its an early or late model.

I was told the later models have a spacer in between the starter and the "rear housing". However i can't find a picture of this spacer. Can anyone possibly snap a picture of the starter area on there 01 or later NV5600 truck?

 

It sounds like the blocking rings (synchros) from 2 to 3 are out. This happened to mine and a complete overhaul is probably what you need. Make sure you put the correct fluid in or you may really have problems!

The 2nd gear wobble is normal at low speed, there is a lot of mass to get going in that box!

The differences from early to late trans are hard to tell from the outside. The spacer is a dead giveaway if you know what you are looking for. I don't have the ability to get a pic for you right now but I'll try.

Also, the later version has an oil passage at the rear of the trans to allow fluid to the rear bearing so overfilling isn't necessary if you have the updated box or a rebuild that has been drilled out. An extra qt doesn't hurt however because these trans get hot when towing.

If I can get a shot of the spacer I'll post it later.

Kurt

 

I have a 2000 3500 with the 5600. Mine does the same thing until it warms up good. If you live in a place that is cold, be a little more gentle with the shift untill the temp comes up. If you push toward third, stop just before you get there and then push again slowly. You'll feel the synchro and the gear stop turning allowing you to get it in with no grinding. Even down here in florida in the cooler season, I have the problem. I also get a little grind going to 4th if I do it in a hurry.

Just got back from Mardi Gras last week with the fiver. It seems when I'm towing I never have the problem even when cold. After towing for 6 hours of so, I can shift it like a close ratio box in a vette. Temperature rise does help.

Dave

 

The problem with the 3rd gear is only apparent on upshifts. I can downshift it like a race car and never get a grind. I changed the fluid to Redline MTL to see if it would help and it certainly shifts easier but the 3rd gear problem is still there. Shifting it slowly does no good. You have to bump 4th first or its gonna grind. The severity of the grind changes the slower you shift but it still grinds.

I think SIXSLUG is right and the synchro/blocker ring is shot on 3rd. I also believe that the bearing in the rear of the case may be going out/damaged. This transmission has been notchy and ground 3rd since i brought it home. Regardless its a synchronized tranny and i have driven one NV5600 that didn't have this problem in fact it shifted almost car like. It makes me think this thing just needs a quality rebuild.

That is what brings me to the identification of the transmission. If this is an early model i will just buy a reman most likely since i can find them for $2000-$3000. Parts alone to upgrade this transmission to the later model (because the synchro rings aren't available for the early) would cost me $2000. If its a later model then i can rebuild it for much cheaper myself.

Here are a few shots from under my truck, excuse the mess my hydroboost blew a seal.

 

Its hard to tell from the pics if you have the starter spacer. I crawled under mine and its pretty apparent if you have it. It is a 1/2" thick plate between the starter motor and bell housing. I have a pic on my cell phone. text me your # and I'll send it if you want it 360-303-5978.

My trans guy says he has never had a problem getting parts for these boxes. A reman of quality should have the holes drilled out for the rear bearing, two or three can be drilled but the tailshaft needs to come off to see them IIRC.

Kurt

 

I had the same problem with my 6 spd. A tech at a local dealer told me to add limited slip diff fluid. I tried one bottle of the Mopar additive, shifts improved. Added a second bottle & it got even better. Every once in a blue moon if I try to shift to fast, I get the 4 to 3 grind, but otherwise it is great.

I am currently running Amsoil 75W90 trans fluid with Amsoil limited slip diff fluid on th advice of a local trans shop.