Bad shifting caused by transfer case???

599 Views 19 Replies 3 Participants Last post by Wontun Splodies, 5 d ago

Ace17

Discussion Starter · 13 d ago

Hello!

So I've got a 1988 gmc sierra with new vortec 350 and a mild cam. Behind it is a recently rebuild nv3500, with the np241c transfer case behind that. I've been trying to solve a shifting issue I've been having, in which i originally thought it was the transmission, but it now doesn't seem to be the case.

Basically what happens is whenever I shift into any gear, it feels like the transmission is temporarily blocking my shifts. I'll push the clutch in, and it'll take a second or two before it goes into gear. It never grinds, but it just doesn't want to go into gear quickly. I had the trans rebuilt thinking it was the problem, but the same problem still occurs. The clutch, pressure plate, throwout bearing, slave/master, and flywheel are all new btw. Then I recently tried something interesting...

I put the transfer case in neutral(with the engine on), and the transmission shifts into any gear like butter. If the transfer case is engaged in 2HI, 4HI, or 4Lo, the transmission now becomes harder to shift. What do you guys think is going on? About 5 or so years ago I bought a rebuild kit for the transfer case and put new bearings, seals etc. in so I can't really figure out what the deal is. Any help is appreciated!!

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total newb

· #2 · 13 d ago

Did the tcase sit properly flush up against the trans or did you ha e to tighten it down to get it to contact?

Known good combo?

Did you put a new clutch/throw out/slave/pilot in with the new motor?

What oil?

With the tcase in gear the input is not spinning which means the clutch and syncros are doing all the work. With it in neutral the tail shaft and input at spinning with the main so it easier for them to line up.

Either something is binding or the clutch isnt fully releasing.

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Ace17

Discussion Starter · #3 · 12 d ago

total newb said:
Did the tcase sit properly flush up against the trans or did you ha e to tighten it down to get it to contact?

Known good combo?

Did you put a new clutch/throw out/slave/pilot in with the new motor?

What oil?

With the tcase in gear the input is not spinning which means the clutch and syncros are doing all the work. With it in neutral the tail shaft and input at spinning with the main so it easier for them to line up.

Either something is binding or the clutch isnt fully releasing.

1) Yep the case set up good against the trans without have to torque it down

2) Known good combo? Not exactly 😅. So this was originally behind a 700r4, and what I did was I changed the input shaft to 32 spline because the original was 27.

3) Yep, new clutch/throw out/slave/pilot in new motor

4) I'm currently using ATF

5) Kind of a dumb question(maybe really dumb) but are you talking about the clutch and synchros inside of the transmission/bellhousing or the transfer case? Are you saying that something is binding in the transfer case??

Thanks for the reply man

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Wontun Splodies

· #4 · 12 d ago

NV 3500s are not fast shifting transmissions. One in good shape anyways.
I have a couple that shift fast....they have no synchros left, are worn out, and both blew up under load in 3rd.
That been said, it's possible your t case is adding extra strain to it. Making it feel worst. But they never shift nice. They don't row gears like a civic.. synchros are slow to mesh ,gates are wide... It's a truck tranny. And not a great one at that. If it drives, drive it.

Ace17

Discussion Starter · #5 · 12 d ago

Wontun Splodies said:
NV 3500s are not fast shifting transmissions. One in good shape anyways.
I have a couple that shift fast....they have no synchros left, are worn out, and both blew up under load in 3rd.
That been said, it's possible your t case is adding extra strain to it. Making it feel worst. But they never shift nice. They don't row gears like a civic.. synchros are slow to mesh ,gates are wide... It's a truck tranny. And not a great one at that. If it drives, drive it.

Yeah I'm sure it's no T-56 or equivalent lol. I'm a pretty relaxed driver so I'm not driving this thing crazy or anything, I guess it just doesn't feel normal. I've driven nv4500s and nv1500s and they feel smoother than this.

I've been compiling a bunch of videos(like a crazy person 🤪) of people driving their nv3500 trucks and watching their shifts, and they seem pretty smooth. Oh, it should also be said that I have the hurst core shifter, which makes the throws a little shorter.

Here's at least some of the videos I've been looking at:

I have a bunch of others, but I guess the point is that this is what I would expect it to shift like, but whenever the t-case is engaged, it temporary blocks my shifts, which makes it feels slow and clunky

Thanks for the response

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Ace17

Discussion Starter · #6 · 12 d ago

Okay so I've added a video of my own to illustrate what I'm talking about. In this video, the engine is running at idle, and I'm attempting to show the shift delay when the transfer case is in 2hi(or 4hi or lo), versus neutral. Keep in mind, this delay is even more pronounced when the vehicle is moving, so trying to drive this thing becomes more of a chore than anything else:

Transmission/Transfer Case Shift Delay

Wontun Splodies

· #7 · 12 d ago

Tokat

Ace17 said:
Okay so I've added a video of my own to illustrate what I'm talking about. In this video, the engine is running at idle, and I'm attempting to show the shift delay when the transfer case is in 2hi(or 4hi or lo), versus neutral. Keep in mind, this delay is even more pronounced when the vehicle is moving, so trying to drive this thing becomes more of a chore than anything else:

Transmission/Transfer Case Shift Delay

Ace17 said:
Okay so I've added a video of my own to illustrate what I'm talking about. In this video, the engine is running at idle, and I'm attempting to show the shift delay when the transfer case is in 2hi(or 4hi or lo), versus neutral. Keep in mind, this delay is even more pronounced when the vehicle is moving, so trying to drive this thing becomes more of a chore than anything else:

Transmission/Transfer Case Shift Delay

okay. I see. That's definitely not the shitty shift I expect from a nv3500.
You sure you have the right....clutch assembly, throw out bearing? Etc. (Stupid, I know, but sometimes.....)
And your positive the tcase spins smoothly in gears? 2h,4h,4l, when it's off the transmission?
Dumb again, but have done myself... Bellhousing is lineup square to the block? Not a bit cock-eyed? (All bolts tight and flanges meeting flush everywhere?
No worn or missing parts in the shifter assembly?

Ace17

Discussion Starter · #8 · 12 d ago

Wontun Splodies said:
Tokat

okay. I see. That's definitely not the shitty shift I expect from a nv3500.
You sure you have the right....clutch assembly, throw out bearing? Etc. (Stupid, I know, but sometimes.....)
And your positive the tcase spins smoothly in gears? 2h,4h,4l, when it's off the transmission?
Dumb again, but have done myself... Bellhousing is lineup square to the block? Not a bit cock-eyed? (All bolts tight and flanges meeting flush everywhere?
No worn or missing parts in the shifter assembly?

Oh yeah, I've definitely spent a lot of cash on transmission parts hoping to solve the problem. If I tally everything up, I'm on my 2nd flywheel(both were new), 2nd clutch/pressure plate/throwout bearing/shift fork, probably 4th slave/master cylinder assembly(I've bought both pre-bled, and assemblies you bleed on your own), 3rd pilot bushing(I've tried both bushing and bearing, and I prefer bushing).

Before I had the trans rebuilt, I took it to a guy who looked inside and basically said he couldn't find anything wrong with it. Also, when I installed the trans, it took some work, but i got it flush up against the motor without having to torque it down.

I guess that's why I'm looking at the transfer case at this point, because I've tried just about everything on the transmission side of things. And I just find it so strange that it shifts like it should if the transfer case is in neutral.

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Wontun Splodies

· #9 · 12 d ago

I'd take a look at how much lash there is in my transmission output shaft, ... And make sure it isn't a tiny bit too long and bottoming in the t case input and causing bind???? Maybe?.. I'm no expert.

total newb

· #10 · 12 d ago

Im wondering if he put the wrong input gear in the tcase but if that was the issue i would think it would persist in neutral or in gear.

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Wontun Splodies

· #11 · 12 d ago

I'm wondering if a thrust washer or shim was put in wrong in the trans? Or forgotten...Tcase in neutral would allow some free play... But in gear . It could????maybe? Push the trans output shaft back in and mesh the gears so they almost lock in the transmission ??? If that makes any sense?

Ace17

Discussion Starter · #12 · 12 d ago

These are great ideas so far!

So I bought a rebuild kit for this transfer case a while back and put in new bearings/seals etc., along with a new 32 spline input shaft, since it originally came with the 27 spline(being behind a 700r4 originally). I took pictures and everything, and was pretty careful, but I wonder if I did indeed forget a washer or shim in the transfer case

I'm thinking it's not the trans because its basically done the same thing before and after being rebuilt, and I imagine a shop that does these transmissions all of the time wouldn't screw that up, but you never know. i might have to tear into this thing and start digging around 😬

total newb

· #13 · 12 d ago

You said that you put a new input in twice.

The issue im wondering is if it was the RIGHT input. 88-93 are different than 94+. But as i said, im not sure that is the issue.

Ace17

Discussion Starter · #14 · 11 d ago

Oh I only put in the new input once. I knew I needed the 32 spline to mate up with the nv3500 so I bought a bearing/seal kit and the new input and did it all at once. Supposedly I ordered the input shaft for the 88-93(it uses the 24mm BD50-8 bearing), I guess I can't be 100% sure I was sent the right one because I had never done it before. I had no idea what to look for. I guess there could also be a chance I got a kit with the wrong bearing as well, but weird thing is that the transfer case bolted up easily.

Ace17

Discussion Starter · #15 · 11 d ago

I looked back at my receipts and it looks like I ordered the correct rebuild kit as well (88-93/24mm bearing)

Wontun Splodies

· #16 · 11 d ago

Hopefully figure it out!
To be honest I never use the 4wd version of the nv3500. Just the 2wd in my drift car. The only time I had shifting this bad was a bind cause by my rear DS being a bit too long and forcing the output shaft back in the case and screwing up with the gear mesh. The trans was worn and beat already and blew up later due to disintegrated thrust washer designed to get things lined up.
I kinda am out of ideas concerning your problem. Total Newb really knows his Chevy stuff. I, myself, really follow is inputs when it comes to shaft swaps, t cases etc..

Ace17

Discussion Starter · #17 · 10 d ago

woah you put an nv3500 in a drift car??? Didn't know those nv3500s could take that stuff

Yeah I think over the next few days I'm gonna tear into it and see what's going on, and hopefully I can pinpoint the problem. I'm gonna look at my old 27 spline input shaft and compare the length and see if something is off.

I'll report back in a few days!

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Wontun Splodies

· #18 · 10 d ago

Yup i did. Few guys around here have. They don't last long. Shit 3rd every few months..5th Everytime you get nasty with it..hates grippy wide tires.... But I get them for free out of trucks we crush......so....made sense at the time compared to a t56. Or a 1500$ adapter to run something else...

Ace17 said:
woah you put an nv3500 in a drift car??? Didn't know those nv3500s could take that stuff

Yeah I think over the next few days I'm gonna tear into it and see what's going on, and hopefully I can pinpoint the problem. I'm gonna look at my old 27 spline input shaft and compare the length and see if something is off.

I'll report back in a few days!

Ace17

Discussion Starter · #19 · 5 d ago

Welp....I think I figured out the problem 😂

I opened up the transfer case and didn't really find anything substantial, so I combed through all of the other possibilities, including maybe the transfer case being torqued down too tight, etc. Then I looked at the driveshaft.. This is an auto to manual swap truck, so while the driveshaft kinda fits, the yoke sticks out 2 inches from the transfer case. And upon doing some further reading, the most you would want is 3/4" to 1" sticking out from the transfer case. So I had another yoke sitting around, and I decided to take the driveshaft out, and just stick the yoke in instead, completely pushing it in, and guess what - it shifts perfectly with the engine running now. My guess is the fact that the driveshaft is just a little too short makes the angle more awkward, and it puts tension on something inside of the case. It's a total bummer because I just had this driveshaft built 😩. Live and learn I guess lol

I'll report back for the fine conclusion once everything is done

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Wontun Splodies

· #20 · 5 d ago

I did say something was binding LOL... didn't think it'd be a driveshaft though..😲

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