NP203 removal and rebuild

[Turbo4whl]

The 464/203 combo. Extremely uncommon. I thought it was '74-only, but really not sure.


@Turbo4whl I always wondered why it was only briefly available. I ASSumed that maybe it had something to do with some kind of backlash in the driveline while going around a turn or something. But that's just a wild ass guess.

Yes, you are right.

What could happen, on a dry hard surface with the 203 in lock making a tight turn, like into a parking space, the drive line locks up and the engine stalls. With the auto trans the truck stops moving, engine does not stall, shift to reverse and back up and unwind the drive line.

The drive line locks on the stick shift so tight, you can not move the trans shifter lever. You can not pull the transfer case out of lock. All the axles are twisted some, putting strong hold on everything. I was thinking I would have to jack a wheel to release the gear boxes. What did work, I put my leg/foot on the trans shift lever, my back against the seat and pushed very hard. Guess I was lucky I did not break the shifter or rail. Put the trans in reverse and back up unwinding the axles.

I have a 76 SM465/NP205 K15 & 78 K25 with the same setup.
Heck, 25 years ago I had a K10 with the overdrive 4-speed/NP208.

This problem only would happen with the full time 203 gear box. I should have stated GM stopped offering the stick with the 203 case, still could definitely get the 205 with the SM465.

* @bucket wins the points!

 

[Chris64]

I finally built a little cradle to hold it level. I think I tried being too clever and made it sit at about 3-4 degrees leaning back to match the transmission. That just made the cuts all more complicated and the trans lift has an adjustment for this. Oh well.

I need to see how much room I have between the cross brace and the mounting surface. I'd like to add a little more material to the opposite side of this picture. The center of gravity is just a few inches off of the corner so more surface area for mounting this whole contraption to the lift would be good.

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[bucket]

You are putting significantly more effort into it than I did. I literally just grabbed some scraps of wood, made some use of the 'ol eye-crometer, tossed them in the saw and then haphazardly ran some deck screws into it all.

I guess I have no shame, lol.

 

[Chris64]

You are putting significantly more effort into it than I did. I literally just grabbed some scraps of wood, made some use of the 'ol eye-crometer, tossed them in the saw and then haphazardly ran some deck screws into it all.

I guess I have no shame, lol.

Oh it was plenty eye-balled .

I'm hoping this tool will work well enough that it won't be a huge effort to pull it back out and maybe clean it up more for more cleanup and/or paint some day. Also, I'm still just assuming I fixed the leaks. It may be coming right back out.

 

[Chris64]

I thought I planned for everything . I got the CG about as good as you can and it's already questionably tippy towards the front.

I rolled it out to my truck following my line of pressure washed oil stain I left from the last trip.

AND...it's now too high to fit under my truck. I had to lift the front left onto blocks and the lift the rear left and then I could barely scoot it under the back of the gas tank! Success.

AND...as I'm eye balling clearances and preparing to do the final lift I realized the front plate of the lift will hit the transmission cross support.

Ugg. I was racing the rain and that was my last chance this weekend. I need to relocated my cradle almost all the way to one side or lift the blocks about 3 inches. Since I already can't easily get it under the truck I have to do the super tippy method. The front mount needs to be projecting about 3" out from that white plate. The wood blocks were planned to leave about an 1-1.5" more than I needed.

Side note: This thing is said to weigh 170-200 pounds. Mine is definitely one of the 200 pounders.

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[Chris64]

So tomorrow will be attempt #2.

Dumb question; I didn't realize until it was out that 2 of the 7 mounting bolts are a bit shorter than the others. I believe the bolts will fit in any of the locations.

Approximate bolt layout:

1-2-3
4---5
6---7

I did find that some bolt holes allow you to screw them all the way in. In spot 5 it will actually touch the gear, but that isn't while mounted in the car. The plate spaces the bolts back 5/8" and that's far enough to clear. Does anyone know where those short bolts normally go? I will probably put one in that 5 spot if I don't get more intel.

 

[Chris64]

Got it reinstalled! I still need to add fluid so I can't call it a success yet - but it's not leaking so far!

The best tip I found when trying to figure out how to hold the gasket in place: Get some 3/8 16 (same as bolts) threaded rod and loosely put them in a few of the holes. This holds the gasket in place and helps alignment. It worked like a charm.

I still need to figure out which other spot should get the shorter bolt though. I still need to make my shifter so they're not fully torqued yet.

But, another dumb question - Parking brake routing. I had to loosen it all up to get it around the drive shaft. There were two hangers, one of each side about mid way down the run. I can't find any examples of this online. I was hoping they would just stay in place but they both fell out. I drew in this picture where they go approximately. I don't see any indicator on the chassis or cable where these where were located. There's two spots that look obvious and they could go in from the bottom of the frame or the top (inside the channel - down).

This whole parking brake setup seems really sketchy. Is it fine? Is there an upgrade for it? I guess it's working so that's probably fine.

Where the red circles are where these would be - there are no brackets as indicated.

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[75gmck25]

IIRC, my ‘75 K25 has brackets like in the diagram, and they are riveted to the frame. They would not just fall off. Are yours nor bolted or riveted on?

I need to do some other work on/under the truck today and I’ll see if I can get a picture.

 

[Chris64]

IIRC, my ‘75 K25 has brackets like in the diagram, and they are riveted to the frame. They would not just fall off. Are yours nor bolted or riveted on?

I need to do some other work on/under the truck today and I’ll see if I can get a picture.

They're just wire hanger things like you see in the picture (#9) except smaller and shorter. One side has an open loop to hold the cable and the other has a 100 degree bend so it can hook on something if under tension. I don't see any wear marks on the cable or the frame though.

Update: I figured it out. There are little angle brackets only about a foot from the corners. The hangers fit on those just right and there were wear signs that matched.

 

[Jim 78K5]

I couldn't find anyone discussing this. It will probably be a whole series of questions because, of course, I've never done this, but what could possibly go wrong?

I'm pulling an NP203 from a AT350 transmission. I started this evening draining it(about 2 quarts) and removing the drive shafts which went mostly smooth. The little bearing cap on the rear holding the needle bearings did come off. A few needles fell out. I'm pretty sure I found them all but they might've picked up dirt. I planned to just parts clean them and repack with new grease. Is that fine or should I replace? It looks fine.

Next will be to remove the transfer case. I count 7 bolts holding it on which some will be really rough to reach. I was going to buy a HF trans jack since I'm doing this solo and for $79 seems easier than rigging something with 2x4's. Plus I could always use it in the future.

I'm trying to cure a pretty bad leak. Most of it seems like it's leaking from the speedo shaft output. I just bought a gasket and seal kit so hopefully that will do it.

While I was down there I noticed a serious crack on the flywheel cover right next to the starter. Initially I though it was part of the transmission but this seems like no biggie...or is it?

Anyway. I'll try to post pics or video if I can.

You better be real careful the Transfer case alone weighs almost 300 Lbs.
These cases are a notoriously known to leak.

 

[Chris64]

This project is still going (I don't have a lot of free time, I'm sure we can all relate).

I built my first gen dual lever conversion. The cost was almost entirely scrap metal I had floating around.

I started modeling the whole thing up in SketchUp and it was taking forever getting non-stop measurements. So I decided to just wing it.

Appreciate my spacious workbench. This was the clean spot.

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I don't want to hear anything about my welds. I'm sure they'll hold. It's 1/4" thick steel so it's super rigid. I made some Delrin bushings. I happen to work near a place that sells remnants so a 3/4" x 12" bar was around $2.99. It's super heat resistant and needs no lubricant and good for not vibrating.

The plate idea was really just copying the original. This way I could easily align the bottom and then once installed I could align the top. It also has a 3/4" bar added to it so it wouldn't have a lot of play. It doesn't. It's really rigid.

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Here it is all assembled. I tried to find another Hurst lever. I can buy them new for around $125 or used for around $75, or a shorty for around the same. I just band sawed one with 1/4" instead to see what I like.

I couldn't find a second shift knob that I liked. Can you guess what my plan is? There are clues.

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Here it is installed and pulled all the way back. The left knob is LOC back. The right knob is L-N-H (High, back). I decided to angle it so the knobs wouldn't interfere with each other. This caused a problem of the lower bolts not clearing the body. So I welded in threaded rod for the lower part. I may move them back together after I figured out the knobs. I'd prefer they were symmetrical but I think it looks OK.

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I'm still trying to figure what to do with the boot. I was thinking of sewing something with the same vinyl that I put on the dash.

 

[bucket]

Shifter Boot, Twin-Stick P/N TSB

Shifter Boot, Twin-Stick

jb-custom-fabrication.myshopify.com

Shifter Boot, Twin-Stick, Tailored P/N TSBT

Shifter Boot, Twin-Stick

jb-custom-fabrication.myshopify.com

 

[Chris64]

I finally completed my shifter distraction and got everything bolted back and lubed. No leaks so far (knocking on wood).

Here's the underside. I'm most impressed with the label on the NP203. That was under 1/2" of crud.

Now that I look at it I don't think I plugged the vacuum hose in on the transmission

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[Chris64]

Knob time!

My dad bought this <$100 CNC engraver on Amazon and didn't understand how to use CAM software or program G-code so he gave it to me to figure out. So I finally gave it a try.

First let me state that CAM software has not been keeping up with 3d print slicer software at all. Slicer software is insanely easy to use and basically free. Cam software is poorly laid out, finicky, makes buggy g-code and super expensive. The one I used to use, SheetCam, is virtually unchanged since 2004 when I had it before and still one of the better choices.

Anyway, I ended up find Easel which was a web based solution and it was just OK. I had to modify the g-code and convert every LF to a CRLF...but it got the job done well within the 15 free trial.

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This machine is in no way meant to be used on aluminum and will say don't do it...so of course, I did. It works fine...at 60mm/min with a depth of .08mm. That is slow if you're wondering. Easel didn't offer a finishing pass which is lame. Anyhoo, it worked for what I needed on some random scrap of aluminum I found. I did break a few blades getting the speed right. The letters were cut with a 1/32 2 flute. The border was a 1/8" 2 flute.

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And then sprayed flat black and sanded (Note: the first battle damage on the table - whoops):

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Next came the knobs. My dad also had a mini lathe that he let me borrow. If I only had floor space.

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Here's the finished knobs. I would've made the plate smaller in hindsight but these will do the trick for now. For threads I turned a couple 3/8-16 couplers down to 1/2" and epoxied them in the bottom.

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To be continued...

 

[Chris64]

continued...And finally I borrowed my daughters sewing machine to make some little shift boots. I'm not totally happy with them. These are actually the seconds version. The first covered the whole lever so I just made these the same with half the height. Well, that didn't allow for enough material and the hole is too big, BUT they'll do for now. I'm thinking about 3d printing some TPU flex accordion style instead. Future project.

Anyway I finally started it all up and went through all the gears and it had no problem at all like I used to. I was afraid to touch it before.

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