NP203 question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

379redneck · 03-10-2011, 04:54 PM

I just found out my truck has an NP203 transfercase on it. From what I have read so far online this is a full-time 4wd setup. My truck has manual locking hubs on it, and it sounds like that isnt normal unless it has a part time conversion in it. The hubs that it has are superwinch and they look like they have been there a long time.

Would it be better with the part time kit or as full time?
What are the advantages of full time and part time 4wd?
Should I take off the manual hubs and replace them if it still has the full time setup?
Thanks

duallyjams · 03-10-2011, 05:55 PM

Unless you are rock crawling or full time off road you do not need full time 4x4 unless you want to burn a lot of gas.

OrrieG · 03-10-2011, 08:06 PM

If it has part time conversion and you put in full time "plugs" (can't think of term they aren't really hubs) you will destroy the transfer case or something else. I think if you turn the hubs free and do NOT have a full time kit all that happens is the front drive line turns and you do not move. If you have the hubs turned to lock and DO have a part time conversion you have been very lucky driving on pavement.

DirtyLarry · 03-10-2011, 08:28 PM

As unpopular as the 203’s were (outside of 203/205 doublers) it would be very odd that an 1987 K20 would have a swapped in a TH350 and NP203. Are you sure it isn’t a NP208? Is the case aluminum or cast iron?

MrBeast · 03-10-2011, 09:49 PM

Quote:

Originally Posted by DirtyLarry

As unpopular as the 203’s were (outside of 203/205 doublers) it would be very odd that an 1987 K20 would have a swapped in a TH350 and NP203. Are you sure it isn’t a NP208? Is the case aluminum or cast iron?

I belive 1980 was the last year of the 203.

the 205 was used 1968/9 - 1991. I think the 208 was from 1981 - 1991.

the dates are aproximate, I am pulling this out of my head, not a reference.

BLAZERMAN · 03-10-2011, 10:14 PM

Quote:

Originally Posted by MrBeast

I belive 1980 was the last year of the 203.

the 205 was used 1968/9 - 1991. I think the 208 was from 1981 - 1991.

the dates are aproximate, I am pulling this out of my head, not a reference.

1979 was the last year for the NP203... All 1980 GMs used the NP205

MrBeast · 03-10-2011, 10:35 PM

Quote:

Originally Posted by BLAZERMAN

1979 was the last year for the NP203... All 1980 GMs used the NP205

Thats right, 80 was kind of a goofy year too for them, with the rounded fenders, but having the square headlights.

379redneck · 03-11-2011, 03:31 AM

I thought it said 203 on the transfercase and it looks exactly like a 203, not so much a 208 tho and not at all like a 205. What first got my attenion was how to drain it since it only has one plug in the middle. The plate on the floor says
Low Lock
Low
Neutral
High
High Lock

So I should just junk it and get a 205?
How do you do a doubler and whats the point of it?

MrBeast · 03-10-2011, 09:50 PM

Oh, and the 203 does not like being in 2wd mode, even with the part time kit, it still will slowly destroy its self.

If you have a 203, I strongly sugjest you aqqire a 205 and do a doubler.

OrrieG · 03-11-2011, 09:05 PM

Quote:

Originally Posted by MrBeast

Oh, and the 203 does not like being in 2wd mode, even with the part time kit, it still will slowly destroy its self.

If you have a 203, I strongly sugjest you aqqire a 205 and do a doubler.

Guess that 85K I put on mine over 15 years was waste of a good rebuild! Checked out the inside and its still good to go so it went back in. I've got a Doug Nash shaft kit that makes it a true in-out box.

winchster · 03-11-2011, 10:41 PM

The 203 is fine for most everybody that doesn't crawl rocks and try to self destruct their trucks. Nothing wrong with that if you do, I'm just sayin...

The 203 with the part-time kit AND manual hubs will last 99% of users just as long as a 205 will.

darkolive71 · 03-11-2011, 10:54 PM

If the 203 isn't giving you any trouble I wouldn't replace unless you are spending a lot of time off road or putting a lot of torque through it. I think it is recommended that a 203 that has been converted to part time be put in 4wd every so often for lubrication purposes. Can someone confirm this?

darkolive71 · 03-11-2011, 10:58 PM

scooter122983,

I didn't see your reply until after I posted mine. I guess you confirmed what I had heard.

379redneck · 03-12-2011, 01:59 AM

Im not sure if it has the conversion kit in it. Im going to be draining it tomarow.

I should use motor oil? I already bought atf for it, thats what I was told by a few people to put in it. What is the best thing for it?

Is there any way to tell while I am draining it if it has the coversion or not?

This truck has been pieced together over the years so I have no idea what it has done to it and im trying to get a good idea as to whats in it.

LONGHAIR · 03-12-2011, 08:29 AM

Quote:

Originally Posted by MrBeast

Oh, and the 203 does not like being in 2wd mode, even with the part time kit, it still will slowly destroy its self.

If you have a 203, I strongly sugjest you aqqire a 205 and do a doubler.

That is just not so....Converted NP203s can and will last for many years. I have personally installed many dozens of these kits and never had a failure.

Quote:

Originally Posted by winchster

The 203 is fine for most everybody that doesn't crawl rocks and try to self destruct their trucks. Nothing wrong with that if you do, I'm just sayin...

The 203 with the part-time kit AND manual hubs will last 99% of users just as long as a 205 will.

Yes^^^

MrBeast · 03-12-2011, 02:09 PM

Quote:

Originally Posted by OrrieG

Guess that 85K I put on mine over 15 years was waste of a good rebuild! Checked out the inside and its still good to go so it went back in. I've got a Doug Nash shaft kit that makes it a true in-out box.

Quote:

Originally Posted by LONGHAIR

That is just not so....Converted NP203s can and will last for many years. I have personally installed many dozens of these kits and never had a failure.

Having experince with them you all probably know better than I do. My information is based off an article I read in four wheeler a few years back, the article stated that when setting up the 203 as a part time that the inner differential was prone to grenading because for what ever reason it did not like having the front shaft not spinning.

Or now that I think about it perhaps it was the reason you should not run locking hubs with out the adapter kit.

I cant remember.

I have had 3 of them, they all 3 came behind TH350's and when the TH350 grenaded, I yanked em and installed a SM465/NP205. Anyone who likes to play off road knows that it doesnt take much to roasty toasty a TH350.

Much of my bias comes from my bad experinces with chain driven transfer cases. I could build a road block with all the NP208's I have grenaded.

And such is why I am a fan of the 203/205 doubler, its all gear driven, no chain to mess with, and its a pretty stout setup.

379redneck · 03-11-2011, 04:08 AM

Money is a problem right now. Would it be easier and cheaper to just put in a 205? What is the range box?
Im new to transfer cases so I dont know to much. What does the doubler do?

MrBeast · 03-11-2011, 10:26 AM

A doubler takes the gear box off of the 203, this box has a either direct 1:1 drive, or a 2:1 low range.

If you set it up as a doubler, it means that with the 1.96:1 low range of the NP205 you will have almost a 4:1 low range.

scooter122983 · 03-11-2011, 10:53 PM

throw it in 4hi every fill up for a few miles and you would be fine with that old conversion. With the new conversion it allows the shaft to pump oil to the rear output bearing. It is a very strong case and can give you plenty of reliable service through the years and only requires simple motor oil for its lubrication. If it ever tanks then is time for a transfer case swap. But a running 203 is nothing to be ashamed of. The only time people break them is when they dont use 4hi every 500 miles to pump the oil, and even then it is normally the output bearings that blow.

03-10-2011, 04:54 PM	#1
379redneck Registered User Join Date: Sep 2010 Location: Kingston, PA Posts: 394	NP203 question I just found out my truck has an NP203 transfercase on it. From what I have read so far online this is a full-time 4wd setup. My truck has manual locking hubs on it, and it sounds like that isnt normal unless it has a part time conversion in it. The hubs that it has are superwinch and they look like they have been there a long time. Would it be better with the part time kit or as full time? What are the advantages of full time and part time 4wd? Should I take off the manual hubs and replace them if it still has the full time setup? Thanks __________________ 87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now

03-10-2011, 05:55 PM	#2
duallyjams Registered User Join Date: May 2007 Location: Deale Md Posts: 4,663	Re: NP203 question Unless you are rock crawling or full time off road you do not need full time 4x4 unless you want to burn a lot of gas. __________________ James 63 GMC V6 4speed carryall 65 chevy swb bbw V8 auto 68 K20 327/4 speed, buddy buckets 2002 GMC CC Dually Duramax 64 GMC lwb 3/4 V6 4speed SOLD 66 GMC swb bbw buddy buckets SOLD IG duallyjams The only thing that stays the same is constant change!

03-10-2011, 08:06 PM	#3
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: NP203 question If it has part time conversion and you put in full time "plugs" (can't think of term they aren't really hubs) you will destroy the transfer case or something else. I think if you turn the hubs free and do NOT have a full time kit all that happens is the front drive line turns and you do not move. If you have the hubs turned to lock and DO have a part time conversion you have been very lucky driving on pavement. __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project Last edited by OrrieG; 03-10-2011 at 08:07 PM.

03-10-2011, 08:28 PM	#4
DirtyLarry Windy Corner of a Dirty Street Join Date: Jun 2003 Location: Pueblo West, Colorado Posts: 2,926	Re: NP203 question As unpopular as the 203’s were (outside of 203/205 doublers) it would be very odd that an 1987 K20 would have a swapped in a TH350 and NP203. Are you sure it isn’t a NP208? Is the case aluminum or cast iron? __________________ Current vehicle collection: 1978 Chevrolet K10, 8.1L, NV4500, NP205 1989 Chevrolet Suburban, 8.1L, NV4500, NP241 1993 Chevrolet C1500 Sportside, TBI 7.4L, 4L60E 2001 Chevrolet K2500HD, Ext Cab, SWB, 8.1L, ZF 6 speed 2014 Chevrolet Impala LTZ 3.6L Vortec 8.1L because life is too short to tolerate underpowered vehicles Instagram

03-11-2011, 03:31 AM	#8
379redneck Registered User Join Date: Sep 2010 Location: Kingston, PA Posts: 394	Re: NP203 question I thought it said 203 on the transfercase and it looks exactly like a 203, not so much a 208 tho and not at all like a 205. What first got my attenion was how to drain it since it only has one plug in the middle. The plate on the floor says Low Lock Low Neutral High High Lock So I should just junk it and get a 205? How do you do a doubler and whats the point of it? __________________ 87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now

03-10-2011, 09:50 PM	#9
MrBeast high-Tech Red Neck Join Date: Feb 2008 Location: Livingston, MT/On my boat WA/BC/AK Posts: 2,294	Re: NP203 question Oh, and the 203 does not like being in 2wd mode, even with the part time kit, it still will slowly destroy its self. If you have a 203, I strongly sugjest you aqqire a 205 and do a doubler. __________________ "He used to be a pretty nice feller, now he's a welder!"

03-11-2011, 10:41 PM	#11
winchster Registered User Join Date: Jul 2006 Location: Fort Worth, TX Posts: 220	Re: NP203 question The 203 is fine for most everybody that doesn't crawl rocks and try to self destruct their trucks. Nothing wrong with that if you do, I'm just sayin... The 203 with the part-time kit AND manual hubs will last 99% of users just as long as a 205 will. __________________ '49 AD 5 window deluxe cab sitting on a '78 K5 chassis Support our troops, stand behind 'em or get in front of 'em. What country can preserve its liberties if its rulers are not warned from time to time that their people preserve the spirit of resistance?

03-11-2011, 10:54 PM	#12
darkolive71 Registered User Join Date: Jan 2011 Location: Cape Girardeau, MO Posts: 18	Re: NP203 question If the 203 isn't giving you any trouble I wouldn't replace unless you are spending a lot of time off road or putting a lot of torque through it. I think it is recommended that a 203 that has been converted to part time be put in 4wd every so often for lubrication purposes. Can someone confirm this?

03-11-2011, 10:58 PM	#13
darkolive71 Registered User Join Date: Jan 2011 Location: Cape Girardeau, MO Posts: 18	Re: NP203 question scooter122983, I didn't see your reply until after I posted mine. I guess you confirmed what I had heard.

03-12-2011, 01:59 AM	#14
379redneck Registered User Join Date: Sep 2010 Location: Kingston, PA Posts: 394	Re: NP203 question Im not sure if it has the conversion kit in it. Im going to be draining it tomarow. I should use motor oil? I already bought atf for it, thats what I was told by a few people to put in it. What is the best thing for it? Is there any way to tell while I am draining it if it has the coversion or not? This truck has been pieced together over the years so I have no idea what it has done to it and im trying to get a good idea as to whats in it. __________________ 87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now

03-11-2011, 04:08 AM	#17
379redneck Registered User Join Date: Sep 2010 Location: Kingston, PA Posts: 394	Re: NP203 question Money is a problem right now. Would it be easier and cheaper to just put in a 205? What is the range box? Im new to transfer cases so I dont know to much. What does the doubler do? __________________ 87 GMC Sierra 2500 4x4 350/TH350/NP203 Flow Tech long tube headers, throttle body spacer, Edelbrock Performer cam, true dual Flowmaster 40s, 6 inch Superlift suspension lift 2000 silverado extended cab stepside 5.3l. Stock for now

03-11-2011, 10:26 AM	#18
MrBeast high-Tech Red Neck Join Date: Feb 2008 Location: Livingston, MT/On my boat WA/BC/AK Posts: 2,294	Re: NP203 question A doubler takes the gear box off of the 203, this box has a either direct 1:1 drive, or a 2:1 low range. If you set it up as a doubler, it means that with the 1.96:1 low range of the NP205 you will have almost a 4:1 low range. __________________ "He used to be a pretty nice feller, now he's a welder!"

03-11-2011, 10:53 PM	#19
scooter122983 The Man The Myth The Mystery Join Date: Jul 2007 Location: Des Moines, IA Posts: 114	Re: NP203 question throw it in 4hi every fill up for a few miles and you would be fine with that old conversion. With the new conversion it allows the shaft to pump oil to the rear output bearing. It is a very strong case and can give you plenty of reliable service through the years and only requires simple motor oil for its lubrication. If it ever tanks then is time for a transfer case swap. But a running 203 is nothing to be ashamed of. The only time people break them is when they dont use 4hi every 500 miles to pump the oil, and even then it is normally the output bearings that blow.



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