np203 questions

[Srubydo1986]

Im in the middle of a build of a once a 1986 4x4 1/2 ton automatic 700r4 350 truck. Its now going to be a 3/4 tonish 4x4 granny 4 speed with 6.2 diesel also swapped axles.

now i have a np203 which i know is all time 4x4 but i have manual locking hubs would that be basically 2wd or do i need to do something about this?

[Rbcustoms]

That would alowed the front hub to turn free, but your gearz are still going to trun. You can run a 208 or a 205 they would work better

[bikes&bowties]

You can get a kit to "part time" you no203
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[b454rat]

if you put lockouts up front and leave them open or unlocked, you will not go anywwhere. The front driveshaft will spin while the rear does nothing. You need to get the part time kit that goes into the t-case. There are two, one is better than the other and more expensive, but if you plan on adding bigger tires and offroading, gonna want it.

[Srubydo1986]

Originally Posted by b454rat

if you put lockouts up front and leave them open or unlocked, you will not go anywwhere. The front driveshaft will spin while the rear does nothing. You need to get the part time kit that goes into the t-case. There are two, one is better than the other and more expensive, but if you plan on adding bigger tires and offroading, gonna want it.

that is what keeps confusing me so if i run the front hubs unlocked and the t case in gear the truck will not move?

[b454rat]

Yep driveshaft will spin. I think that the front spins first, then power goes to the rear. Not real sure how it works. I had a truck that had the 203, swapped in a set of lockouts, unlocked them and put it in, the front shaft was spinning like the truck was doing 60. Only way to drive the truck is to put it in 4 lock, then sends power to both front and rear.

[RandyP]

Well, my 79 K5 has the 203, the front hubs are unlocked and it is in HI, moves just fine. Unless it is just so worn out that it is actually in HI LOC, but I don't think it is. One notch up from where I have it is Neutral, and I've had to do that a few times recently to push it around the shop after making it a non start for various reasons.

[ray_mcavoy]

Originally Posted by b454rat

Yep driveshaft will spin. I think that the front spins first, then power goes to the rear. Not real sure how it works. I had a truck that had the 203, swapped in a set of lockouts, unlocked them and put it in, the front shaft was spinning like the truck was doing 60. Only way to drive the truck is to put it in 4 lock, then sends power to both front and rear.

NP203 has a differential inside that splits power to the front & rear driveshafts. Just like the differential in a rearend splits power to the left & right axles.

So when you put a set of lockout hubs on a truck with a 203 and leave them unlocked, it's basically the same thing as having one wheel jacked off the ground with an open differential.

When the 203 is shifted to either Hi Loc or Low Loc, it locks out that internal differential and will therefore allow the truck to drive with the hubs unlocked.

As has already been said, there are a couple of kits available to convert the 203 over to part time operation. The kits basically eliminate that differential and make it so power always goes to the rear driveshaft. The "Hi" & "Low" positions become 2Hi and 2Low, while the "Hi Loc" & "Low Loc" positions become 4Hi and 4Low.

Or, depending on how you plan to use the truck, you could leave the 203 as-is and replace the lock out hubs with the solid splined "pucks" that were used in factory 203 equipped trucks.

[hatzie]

The NP203 has a lockable differential just like front and rear axles. In 4HI and 4LO it's just an open diff sending power to the driveshaft that turns easiest so it doesn't bind up on smooth pavement. In 4HI Lock and 4LO Lock the diff locks and it operates like any other transfer case in 4x4. If you unlock the hubs the truck will not move in 4HI or 4 LO. I don't know what happens if you are in the 4HI Lock or 4LO Lock positions. If it moves in the "Lock" positions it may not be good for the internal diff.

The NP203 is heavier than a dead horse... Mile Marker made a full shaft part time kit for the NP203 the cheaper shaftless kits don't have good reputations. As a bonus you do get a 2LO position with a converted NP203.

The NP208 is cheap and does have a much better low range 2.76:1 when compared to the 203 & 205 that have 1.96:1 low range and should hold up fine behind the 6.2.

Ray posted the same thing while I was writing.

[Redcap]

Originally Posted by hatzie

The NP203 has a lockable differential just like front and rear axles. In 4HI and 4LO it's just an open diff sending power to the driveshaft that turns easiest so it doesn't bind up on smooth pavement. In 4HI Lock and 4LO Lock the diff locks and it operates like any other transfer case in 4x4.

The NP203 has to have a part-time kit installed and it's heavier than a dead horse... Mile Marker made a full shaft part time kit for the NP203 the cheaper shaftless kits don't have good reputations.
The NP208 has a much better low range 2.76:1 when compared to the 203 & 205 that have 1.96:1 low range and should hold up fine behind the 6.2.

The 208 is also significantly weaker than a 205. I have seen more than a few 208s leave their guts behind.

[hatzie]

Originally Posted by Redcap

The 208 is also significantly weaker than a 205. I have seen more than a few 208s leave their guts behind.

I've plowed snow commercially with Ford, Dodge and GM trucks that had NP208 & NP241 cases. Snow plowing is rough on everything. The transfer cases held up for 150k+ miles of commercial snowplowing and landscape trailer towing. In that same number of miles we went through 2-3 transmissions and a couple front axles. Low range with the newer NP208 & NP241 trucks was noticeably better for pushing snow around than the old NP203 Dodge Power Wagon we kept as a backup rig.

[Ronaldo]

Anyone know where I can a get a shaft part time conversion kit for a 203?
Ron

[bilfman]

Remember np203s use light oil 30 weight tops i prefer 10-40. ALso if you part time it get some half inch fittings and extend the filler 2 inches higher so the case holds 2 inches more oil. The part time kit stops the pump in the 203 . The extra oil lets it slosh lube.

[Redcap]

Originally Posted by Ronaldo

Anyone know where I can a get a shaft part time conversion kit for a 203?
Ron

Click here.

Also, nice thread necro.

[motornut]

i dont drive mine everyday, so when i do i drive with my hubs unlocked ,I drive the first 10 min or so with the axles locked ,undo it and they are lubed
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[Ronaldo]

Originally Posted by Redcap

Click here.

Also, nice thread necro.

You dont think I ebayed and Googled it 40 times before i posted on here? Aparantly they dont make the SHAFT kit anymore on the cogs to replace inside the tail shaft...
Ron

[83GMCK2500]

These cogs?

& you're trying to find this shaft kit?

[79Betty]

Your 203 (and mine) has HI, HI LOC, LO, LO LOC. HI is you're in high range 1:1 and have 20% of your power to the front, 80% to the back. HO LOC is an even 50/50 split of power but still in 1:1 gearing. LO is 20%/80% but 1.96 geared. LO LOC is a 50/50 split in that gearing. I personally plan on running a 205 with the full time acle these trucks came origional with. Then all i gotta do is push a lever and BAM 4wd.
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[Ronaldo]

Originally Posted by 83GMCK2500

These cogs?

& you're trying to find this shaft kit?

Yes that shaft .. Dont see where I can purchase it anywhere..Ebay or mile marker. Guess I gotta use the cogs., unless your seeing where i can buy that shaft somewhere????
I dont see it for sale anywhere??
Ron