NV3500 Shifting Issues

[Ace17]

Hey everyone,

So I've got an issue here that seems to have stumped myself, and the rest of the world along with it - but I'll go ahead and post about it anyway lol.

I have a recently rebuilt NV3500 trans(1995) going into a k1500 4x4 pickup, and for some reason, it seems to temporarily block my shifts when trying to shift into gear(especially 1st and 2nd gear). If I'm at a dead stop, and I try to shift into 1st, there's a delay before it lets me go into gear. There's no grinding whatsoever, but for some reason, it takes it's sweet time before going into gear.

I initially bought this transmission for around $500. I put it in, drove it, and noticed that it was doing the whole temporary block thing, but it was also grinding in 3rd gear. I got up the courage and rebuilt it myself, and while it no longer had a grind in 3rd gear, it was still doing the blocking thing. I ended up buying new pilot bearings, new flywheels, new clutches, pressure plates, master/slave cylinders, clutch forks, throwout bearings etc to no avail. I eventually caved and sent it out to be rebuilt by a professional shop, and it STILL does the blocking thing.

Here's where it gets interesting...i did a little test. When I put my transfer case in neutral while idling, and I shifted the transmission, it shifted freely, but when I put it back into 2HI, it did the temporary block again. I took the transfer case completely off and did the test again. With the output shaft of the trans spinning freely, the trans shifted effortlessly. When I put a driveshaft on the output shaft, stopping it from turning, the transmission gave me the delay again. Can any of you think why my trans would be doing this? Do you think it's internal, or external? I thinking it's in the trans, but damn, how could I , AND a "professional" trans rebuilder miss it?

Here's a short video so you can see it in action:

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If any of you have had any experience with this crazy phenomenon, or have any suggestions, I'm all ears!

 

[Erik the Awful]

My guess is that your clutch is dragging. Bleed, bleed, bleed your clutch.

 

[0xDEADBEEF]

I had something similar happen when I switched out the recommended transmission fluid with some super duper ultra synthetic stuff. It was too slick for the synchros to "bite".

(Not an NV3500 though.)

 

[Ace17]

My guess is that your clutch is dragging. Bleed, bleed, bleed your clutch.

Yeah I've been through a bunch of different slave/master cylinder combinations, and eventually opted for the pre-bled system you just install without having to bleed it at all. The pre-bled system seems to be the best in terms of pedal stiffness.

I talked to a trans rebuilder and he had me go through a few tests(like starting the truck with it in first gear while pressing the clutch), and he concluded that it wasn't dragging. I guess I'm still not sure though

 

[Ace17]

I had something similar happen when I switched out the recommended transmission fluid with some super duper ultra synthetic stuff. It was too slick for the synchros to "bite".

(Not an NV3500 though.)

Yeah I initially tried a bunch of different fluids since that was the easiest thing to do(Penzoil synchromesh, amsoil 5w30 manual transmission fluid, royal purple synchromax, and GM synchromesh). The best result for me was the AC Delco GM synchromesh stuff, which is priceeeeeyyyy. The royal purple, when at operating temp, felt pretty notchy and awful since it's so thin

 

[Erik the Awful]

Possibly the pilot bearing between your input and output shaft is sticky?

You must be registered for see images attach

 

[Ace17]

Woah I never would've thought of that - that's something I might investigate. Thanks for the suggestion

 

[Ace17]

I've got a random question for you folks (just trying to look at all possible angles..) - have you ever bought a pre-bled clutch master/slave system that still required further bleeding?

 

[Erik the Awful]

The only pre-bled kit I've bought is still sitting on top of my NV3500 in the corner of the shop.

 

[barry_g]

brand new, and it looks like a short throw of a core hurst.
did not know thrust could bother these.
there is no other excuses that I can think of...
I am thinking your shifter base off by 1-2mm might notice something and go out of align to the tightness of being new.
if a shaft was bent sideways, it would be offcentric, and your shifter going crazy in the wobbles.

I am at 393k.. gave mine a hurst at around 350k.
mine is a 96..not sure when the last update for these was.
they were setup with sensors and nitirided (?) for the extra hp by 96.
it seems infinite to me, no end in sight, noisy whining like a supercharger included.

follwing this thread, it is interesting.
I recently found the nv3500s max hp and torque are identical to an old allison at545.
the 22k pound max limit trans found in school buses and topkicks or gmc 6000 etc.
you jst can't use overdrive or strain reverse...that is the weakest links.

food for thought.
I have proven this is not a weak transmission at all. Could be my year of it...direct swappable to 2007.
hope you find it. optimistically, the problem is tight...not sloppy.

try loosening shifter base, pressure it to the right, and tighten it down while pressured...and maybe the other dierction. It seems something precise is going on there.