Np203 part time conversion?

[1979 K10]

There used to be 2 part time kits available to change the np203 from full time to part time. I did the cheaper mile marker kit which you could convert the tcase from full to part time while installed in the truck. Took an hour or two but super easy and straightforward, you just swap a gear which is accessible under a cover on side of case and then install some round needle bearings at the tail shaft making sure you get the correct amount or preload. Kit comes with lockable hubs that replace the full time assembly on corporate 10 bolt front axle. I did this kit and didn’t notice any mpg improvement. I had high hopes but that didn’t help realize any improvement lol

The kit did improve tight turning on pavement (no binding, accelerated tire wear) and most of all front axle unjoints will last forever since you’re not constantly powering the front axle.

NP203 becomes 2WD Loc / 2WD /N/ 2WD Lo / 2WD lo lock if front hubs unlocked.

4WD Loc / 2WD /N/ 2WD Lo / 4WD Lo Loc when front hubs locked and engaged.

NP203 Transfer Case Fixing Up a Heavy Favorite​

There was more to that article but only the first page loads for me. There was a better kit offered that requires more work (changing out shaft inside transfer case) and removal of case from truck but that kit has been discontinued for several years.

More info NP203

New Process 203 Transfer Case Tech: Off-Road.com

As Bullet Proof as the NP-205... Almost.

www.off-road.com

BillaVista.com-Transfer Case Doubler Tech Article by BillaVista

 

[1979 K10]

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79 Chevrolet K10 Blueprint 400 sbc startup

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Stock 400 and truck walkaround

1979 K10 Silverado walk around 2" lift front 3" lift rear 33" BFG KO2

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Not to derail thread but I just put a blueprint sbc 400 in it so will see how long that part time conversion holds up going from 185hp / 300tq from stock 400 to 515hp / 509 tq from the dyno sheet on the new BP4002CTC1 engine.

 

[AuroraGirl]

find a np208 and th350 combo from a 1981+ square and swap that in, it will lighten it up a lot and then its a part time case. but you need to address the front hubs of course, still

 

[GTX63]

It for sure needs a tune up, for a supposedly fresh rebuilt qjet I’m having a lot of problems with stalling and bogging under load. I assumed the full time would make me get 4-6ish mpg and I’d really like atleast ten lol

10 mpg should be the norm with an engine in tune, ie good plugs, wires, filters, carb etc.
A generation or more ago, rebuilding a Qjet was second nature to a lot of folks. Now, many squarebody owners are trying to figure them out for the first time. Installing the rebuild kit was the first half of the job; getting it dialed in is where many struggle.

 

[Big Ray]

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79 Chevrolet K10 Blueprint 400 sbc startup

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Stock 400 and truck walkaround

1979 K10 Silverado walk around 2" lift front 3" lift rear 33" BFG KO2

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Not to derail thread but I just put a blueprint sbc 400 in it so will see how long that part time conversion holds up going from 185hp / 300tq from stock 400 to 515hp / 509 tq from the dyno sheet on the new BP4002CTC1 engine.

Love your truck. Just something about a 400, just don't want to go back to a 350...

 

[triplel43762]

The place I bought, had a shaft replacement kit for a 203 nib. If interested I’ll go check it out

 

[Big red square]

There used to be an NP203 conversion kit that swapped the entire shaft inside the NP203, but now they only sell the 501 kit that uses four pawls that you install inside. It is not as strong, but should still hold up fine. It’s not supposed to be hard to install. You will also need to install a kit to allow the hubs to be unlocked manually.

I have an unconverted NP203, but couldn’t tell you how much it affects gas mileage. I’m using full synthetic in the transfer case, but most of the drag is probably coming from the front axles and hubs.

Why full synthetic?

 

[74Blaze]

It's odd how they put lower gears in the older nonoverdrive rigs and higher gears in the overdrive rigs.

They did that in the late 70's and early 80's to lower their fleet fuel mileage to meet EPA regulations. The reason that International dropped the Scout is because they had no "economy cars" to average in with them like the automakers did.