[ratmonkey]

You will absolutely need an fsm that covers this transmission. The dis-assembly and reassembly procedure covers 42 pages. All but a very few illustrations are clear and concise, I only noted one error in the inspection/repair area and one slight omission in the rebuild area.
This is in a 2001 dodge ram fsm, I do not know if there was a change between earlier than 99 nv3500's and 2001 to make this technically correct in the 01 manual.
The first error is:

NOTE: The front housing contains the countershaft
front bearing race. The rear housing contains the
countershaft rear bearing race. Be advised that
these components are NOT serviceable items. The
front housing will have to be replaced if the countershaft
bearing race is loose, worn, or damaged.
The rear housing will have to be replaced if the
countershaft rear bearing race is loose, worn, or
damaged

the fsm further goes on to explain that the races are "permanent" press fit into the housing and can not be removed.
correction. the counter shaft bearings and races do come in the rebuild kit. You need a pilot bearing puller to remove the races and a good bearing driver to seat them in. freezing the races is advisable as is heating the case if you can.

you do need all of the special tools the fsm outlines.
if you aren't doing the shift rail bushings, WHICH DO NOT COME IN THE MASTER REBUILD KIT, you don't need a couple of the special depth setting bushing installers.
shift rail bushings don't seem to wear out much. unless there's more serious mechanical damage than even i noted, i doubt you'll be into that at all.

Taking my time, with a gimpy helper, the correct tools, and a not too cluttered shop the rebuild took around 12hrs. Without the special tools, especially the fixture stand, I don't think i could have gotten it done in less than 18hrs.
If I didn't have the special tools I would have needed to still have a good set of bearing/seal drivers, a bunch of different diameters of pipe for on the press, and three sets of monkey hands.

starting dis-assembly
(I assume you've managed to get this thing on a work bench, with the shift tower already off)
trans MUST be in neutral before you start dis-assembly

• There are either 10 or 12 bolts around the center split of the case to remove, only the ones facing back to front are removed here, the others hold bits into the rear half and need to stay there till later.
• Remove the reverse light switch now while you're nearby.
• Remove the shift rail detent plug. This requires a special puller. Specific procedure is in the fsm, pay attention as pulling at an angle will destroy the tool.

• Remove the shift fork bushing lock bolt on top

.

• Remove the input shaft cover/throw out bearing guide.
• Remove the lock ring around the input shaft holding the input bearing in.

NOTE: there is a lock ring around the od of that bearing you can see from the front. This is only used to set mounting depth and doesn't retain the bearing in the housing. This caused a few minutes of pause when we were trying to disassemble the case originally without the aid of the fsm.

you can now either use a punch to push the locating dowels through and slide the case half off, or use a dead blow to pop the front half off the pins, up to you. You'll need to remove the dowels for re-installation of the case halves anyways later.

This is with the front case half removed and the 3/4 shift fork, shift bushing, and rail already out.

• The shift socket and shift bushing are held on the rail with roll pins.
• Remove the shift socket first.
• Tilt it towards the drivers side so that you have room to drive it through. The fsm calls for a special pin press vise here, a standard set of pin punches works just fine though.
• Now you can rotate the shift bushing enough to drive it's pin out without driving it into a gear.
• At this point you can now pull the shift rail, 3/4 fork, and shift bushing. Remove the shift socket from the tower hole also.

As seen in that last pic.

• Remove the reverse idler retainer bolt and retainer(half moon shaped deal)
• At this point you're ready for that sweet 150$(used) fixture and adapters.
• Make sure the cup for the reverse idler is in the fixture and adjusted kinda low.
• Insert the input shaft and counter shaft into their respective adapters and seat the trans on the fixture while its still horizontal.
• Now get a helper and tip the whole thing up onto the fixture base.
• Adjust the idler cup so that it seats on that shaft.

Now comes the fun.

• Remove the output seal with a slide hammer and corkscrew seal puller attachment.
• Remove output bearing lock ring.

Once again, just like with t-case work, a very good set of lock ring pliers, in a medium or large size, is invaluable here.

• One more bolt retains the reverse idler and now the case just slips off.

[ratmonkey]

I took next to no pictures at this point, we were paying too much attention to what we were doing to remember the camera action. The fsm has excellent illustrations to rely on though.

• At this point you can remove the reverse idler gear and either rebuild it or set aside for later. Follow fsm procedures here, they are very clear.
• Next remove the counter shaft from the fixture.

Inspect the ends for excessive wear on the bearing surfaces. Inspect the gear teeth for sharp edges, burrs, chips, or discoloration. The counter shaft is a one piece unit, if you find any damage replace it. They can be had on ebay, used, for less than 100$ most weeks.

Now we work the main shaft over. Lol.

BE VERY CAREFUL HANDLING THE SYNCHRO HUBS! They have three dogs with springs and small ball bearings in them that retain the shift collar in position.(mainly the neutral position)

I did not think of a way to keep them from coming apart while pulling them, so just wrap the whole thing in a rag and work on a clean surface so you can find the balls and springs when they go flying. Pull them apart as you get to them before setting up for the next pull on the shop press so you aren't chasing them too far

• You can remove fifth gear and it's synchro ring from the back half of the shaft, they aren't pressed on, just slide over the needle bearings.
• Pull the reverse/5th shift collar from the synchro hub being careful about your balls.
• Next pull the main shaft up from the input shaft
  
  it seats in the input shaft on a large set of roller bearings.
  
• Carefully pull the shift collar off the 3/4 synchro hub, minding the springs and balls.
• There's a two piece washer and retaining ring in here(provides oiling to the input shaft/main shaft bearing).

Note/take a picture of the orientation so that you put it back in with the channels spinning the right way.


Follow fsm procedure for removing the gears and hubs from here on, it's clear and straight forward. You need a bearing separator/puller capable of opening to 9", DO NOT USE A 3 JAW PULLER ON ANYTHING HERE!

• Note orientation of synchro rings, hubs, and gears as you are pulling them.
• Now inspect your main shaft, gears, synchro ramps thst are pressed onto the gears, synchro hubs, and the shift collars for wear, mechanical damage and heat damage.

If any of the ramps on the gears are damaged you'll need to buy them separate, they are considered a "hard" part and are not part of the master rebuild kit.

Springs, ball bearings, and snap rings are also not included in the master rebuild kit, they're in a "small parts kit" easily found on ebay as well.

Inspect the main shaft for wear and damage. Especially on the bearing surfaces
you can see the needle bearing surfaces are a little scuffed, but nothing too crazy. i'd say this shaft is in good shape for over 120k on it.

shift collars are directional and gear cluster specific!

Make a note of their orientation and the orientation of the synchro hubs on the shaft. Fifth/reverse synchro hub is directional , the others aren't.

CAUTION: One side of the hub has shoulders
around the hub bore, this side of the hub faces the
front of the shaft. One side of the sleeve is tapered
the tapered side faces the front of the shaft.

• The 5/r collar has the ramped portion forward
• The 1/2 collar has a side marked first gear
• The 3/4 collar has the grooved lip forward

Gears on the main shaft are in this order.

• Fourth is on the input shaft
• Third is the front most gear on the main shaft
• Second is next
• Then first
• Then reverse
• Fifth is last after the lip you see on that main shaft picture

Assembly

• Assemble those shift collar and hub pairings first.

This is the most tedious portion of the rebuild. I wanted to decapitate a puppy during this process. I was swearing like I had tourettes.
Apparently you need fairly large hands to do this job easily, and more patience than I was demonstrating. My friend mike made reasonably short work of them after some trial and error.

• Assemble everything with your new needle bearings and brass lined synchro rings.
• Make sure you let those brass pieces soak liberally in some synchromax fluid

There is a special cup to sit the fifth gear synchro hub on while pressing the other hubs onto the main shaft. I highly recommend purchasing it as it has a lip/seat to make sure things don't go slipping on you.


Careful handling those hubs or you may want to shoot people from a clock tower before the day is out.

The only thing the fsm glosses over in assembly is the synchro set up around the 1/2 hub.
There is a center metal ring with four slots called an intermediate ring on both sides. A bronze friction cone with tabs goes around that, then the synchro ring.

Everything else is covered well to the point of putting it back together on the fixture. Really straight forward and the instructions show every step.