Transfer Case Info for OEM Squarebodies

[RetroC10Sport]

Forgot the 1973-75 Dana 20 there buddy.

 

[HotRodPC]

Hey gents, was drinkin with the family last night and got to talkin with grandpa (who i got the truck from) and he started saying that that np203 full time is only full time upto 35mph????? input please.

That would not be true. Ask yourself, would rear open differential only work up to 35mph? I actually did some research on the NP203 a while ago. It's my understanding that is works just like an open differential when NOT in LOC mode. So consider your front driveshaft as your Left Rear Axle, and consiider your rear driveshaft as your Right Rear axle. Now picture how an open rear differental operates and your Tcase operates the same way unless you HI LOC it.

I think I see where you granddad is going with this. Once the trucking is moving and driveshaft is spinning it would be harder for the Tcase to detemine which axle has least resistance and by theory yeah it's only going to run the rear axle most likely. But, lets say you're moving at 40mph and a front hub, axle or driveshaft happens to break (highly unlikely since it's not the driven axle at this time), then the Tcase is still going to follow the patch of least resistance and tranafer power to that front driveshaft and then you're likely dead in the water, until you put the Tcase in HI LOC so it grabs the rear driveshaft also so you can limp it home.

 

[benjaminearle]

So, for mostly on-road use and the occasional off-road (not boulder climbing or mud pit racing) use like driving through a field to check on cows or go hunting, is there anything very wrong with the NP203? I'm in the process of bying a '79 K1500 with the full-time T-case (I assume this is pretty definitely an N203). See pic.

I looked at one recently that had manual hubs installed on the front to allow 2wd operation. What's the advatage to that if, during normal ops, the open center will put most all of the power to the back anyway?

 

[bucket]

So, for mostly on-road use and the occasional off-road (not boulder climbing or mud pit racing) use like driving through a field to check on cows or go hunting, is there anything very wrong with the NP203? I'm in the process of bying a '79 K1500 with the full-time T-case (I assume this is pretty definitely an N203). See pic.

I looked at one recently that had manual hubs installed on the front to allow 2wd operation. What's the advatage to that if, during normal ops, the open center will put most all of the power to the back anyway?

NP203 is just fine for using the truck for things a stock truck was intended for. The big benefit of using locking hubs on a truck without a part-time conversion is less front tire wear and easier turning. With locking hubs and a part-time kit you get the previously mentioned benefits as well as less front drivetrain wear and a slight improvement in fuel mileage.

 

[HotRodPC]

With an NP203, he can NOT unlock the front hubs if he doens't have a part time kit. Just like you can't run an NP203 without a front driveshaft unless you take the driveshaft out and then use 4 High LoK so that both front and rear outputs are spinning.

 

[bucket]

With an NP203, he can NOT unlock the front hubs if he doens't have a part time kit. Just like you can't run an NP203 without a front driveshaft unless you take the driveshaft out and then use 4 High LoK so that both front and rear outputs are spinning.

Well sure you can. You can unlock the hubs and drive in HILOC all day long, the benefit is less front tire wear because they don't see any of the power and there's less stress applied to them while turning through a corner.

 

[HotRodPC]

Well sure you can. You can unlock the hubs and drive in HILOC all day long, the benefit is less front tire wear because they don't see any of the power and there's less stress applied to them while turning through a corner.

Ok yeah, as long as your in Hi Loc. So it's not an open Tcase.

 

[benjaminearle]

So is it as easy as pulling the front wheels & brakes and replacing the stock hubs with manual lockers? Then i can just unlock and cruise in HiLoc for normal ops? Yes, i'll still have a parasitic loss of economy but i dont mind that as much as chewing up tires and fighting 35s in a parking lot.

Does anyone make some sort of electric locking hubs that can be installed at a reasonable price?

 

[89Suburban]

A set of manual hubs will swap right in. You don't need to pull brakes to do that. Then just run in Hi-Loc.

 

[HotRodPC]

A set of manual hubs will swap right in. You don't need to pull brakes to do that. Then just run in Hi-Loc.

Now hold a sec grasshoppa !!! His might be a different set up. He should have something that looks different than the later models like yours and mine. Almost looks a bit similar to a full floating hub. You might be right, but I"m not 100% certain on that. I've not dealt with those full fixed full time axles. I'm just saying, lets make sure first.

 

[benjaminearle]

So, since this is where I started my NP203 questions, I'll send one more. My truck was delivered this morning and I decided to road test it by driving to work. So, just to make sure I wasn't about to set off down the interstate in 4lo-loc I thought it wise to feel each detent of the t-case and be sure I had selceted 4hi for my pavement drive. So (I'm an engineer, forgive the OCD here), with 4hi-loc, 4hi, N, 4lo & 4lo-loc there should be FIVE distinct positions to the selector handle. Where the F are they, about 1mm apart? Do you have to be rolling uphill in reverse for some to engage? I can only really feel two positions - I'm assuming that's 4hi and 4hi-loc.

I see people write "the shifter sucks" regarding NP203. Can someone explain exactly what kind of "sucking" these folks are referring to and any potential solutions/workarounds (NOT replacing the case).

Many thanks.

 

[bucket]

So, since this is where I started my NP203 questions, I'll send one more. My truck was delivered this morning and I decided to road test it by driving to work. So, just to make sure I wasn't about to set off down the interstate in 4lo-loc I thought it wise to feel each detent of the t-case and be sure I had selceted 4hi for my pavement drive. So (I'm an engineer, forgive the OCD here), with 4hi-loc, 4hi, N, 4lo & 4lo-loc there should be FIVE distinct positions to the selector handle. Where the F are they, about 1mm apart? Do you have to be rolling uphill in reverse for some to engage? I can only really feel two positions - I'm assuming that's 4hi and 4hi-loc.

I see people write "the shifter sucks" regarding NP203. Can someone explain exactly what kind of "sucking" these folks are referring to and any potential solutions/workarounds (NOT replacing the case).

Many thanks.

Your experience is exactly why people say the shifter sucks. The linkage is probably crusty and needs a good cleaning and lubing. There is also an adjustment procedure if cleaning/lubing doesn't help.

 

[tiredtiretodd]

I know I'm posting on an older thread but I'm trying to figure out what transfer case I have so thanks for the info. I'll probably have questions!

 

[HotRodPC]

I know I'm posting on an older thread but I'm trying to figure out what transfer case I have so thanks for the info. I'll probably have questions!

By your year model of truck it should be a NP203 if it's an auto trans, and would be an NP205 if it's a manual trans. Both are cast iron. NP203 is a chain driven full time transfer case, and NP205 is a gear to gear driven part time case. That's if it's OEM and noone has swapped to something else. But there is certainly help here to get it ID'ed for certain.

 

[firebane]

I know I'm posting on an older thread but I'm trying to figure out what transfer case I have so thanks for the info. I'll probably have questions!

Take a picture of the back end of the transfercase.

The NP205 has a distinct center piece with 3 bolts.

Since this thread was bump I'd also like to had there is a distinct difference in the 73-74 NP203 vs the 75 and newer NP203s as well.

This is made apparent when you attempt to convert a 73-74 NP03 to part time and require a spacer from a newer 75+ NP203.

Obviously these spacers are not that easy to come by but they are found on ebay.