School me on the NP203 T-case - Pirate4x4.Com : 4x4 and Off-Road Forum

cur_dog · 08-17-2009, 06:35 PM

On my 76 I have the NP203 with lockout hubs. When I was reading up on the 203 it said it was a full time case. My front drive shaft turns but my hubs are not locked. Do I have to get a conversion kit to get my front drive shaft to NOT turn? Seems like with it turning that would put more wear on things, less MPG (like it's going to get a lot better

) and maybe a little less HP.

Thanks.

Grumpy_old_fart · 08-17-2009, 06:42 PM

yes you need the conversion kit to make the front driveshaft to not turn.

cur_dog · 08-19-2009, 05:32 AM

I thought (newbie) that if it did not have the part time kit in it and the hubs were not locked that it would not work at all. Again, I thought (newbie) that without the part time kit in it that the rear output needed resistance from the front output to work. Probably not making sense here but maybe someone will understand what I'm trying to say.

cur_dog · 08-19-2009, 06:12 AM

I found this. This might explain it better.

The full-time aspect of the 203 is all in the rear section of the unit. The case has an internal differential that selectively splits the power to the front and rear axles when the shifter is not in one of the locked positions. When shifted into Hi-Loc or Lo-Loc, the differential locks to provide equal power to both driveshafts. If you removed either driveshaft and tried to drive the truck with the case in the nonlocked position, the internal diff would send all the power to the yoke with the missing shaft. It’s just like an open rear axle differential, where all the power goes to the tire with the least traction. However, if the case was shifted into a locked position, power would be equally distributed to the front and rear, so you’d be able to drive the rig as long as one driveshaft was still in place.

rcurrier44 · 08-19-2009, 07:13 AM

Is your shaft powered or just spinning? Many front drive shafts will slowly spin because of the fluid movement in the t-case from other gears spinning.

cur_dog · 08-19-2009, 08:09 AM

It's powered

KWTMECH · 08-19-2009, 08:11 AM

See above post number 2

rcurrier44 · 08-19-2009, 08:26 AM

Quote:

Originally Posted by cur_dog

It's powered

So when you have it in the AWD position (unlocked) and the hubs are unlocked then the front shaft can not be turned by hand

well then it sounds like something is screwed up in the t-case and the diff is not working...

cur_dog · 08-19-2009, 08:29 AM

That is correct.

Cubman · 08-19-2009, 11:56 AM

I have a '78 K10 with the 400/350/203 and hubs on the front axle. I have the same problem as cur_dog. When in 4H (unlocked) the front driveshaft is still driven. The t-case will go into 4H-Loc, but will pop out after a few seconds. I don't know if the shifter is out of adjustment or if there is something that is binding when it is locked. Is it safe to bungee cord the t-case shifter in the 4H-Loc position?

smokewrench · 08-19-2009, 01:42 PM

Might be out of adjustment, its not to hard to adjust. I had a similar problem in a truck with a body lift, when in 4L-loc it was hitting the floor. I made the hole a little longer.

08-17-2009, 06:35 PM	#1 (permalink)
cur_dog Wheeler Join Date: May 2008 Member # 113958 Location: Houston, TX Posts: 185	School me on the NP203 T-case On my 76 I have the NP203 with lockout hubs. When I was reading up on the 203 it said it was a full time case. My front drive shaft turns but my hubs are not locked. Do I have to get a conversion kit to get my front drive shaft to NOT turn? Seems like with it turning that would put more wear on things, less MPG (like it's going to get a lot better ) and maybe a little less HP. Thanks.

08-17-2009, 06:42 PM	#2 (permalink)
Grumpy_old_fart Devout Newbie Hater Join Date: Jun 2003 Member # 20147 Location: Oakland Orygun Posts: 6,458	yes you need the conversion kit to make the front driveshaft to not turn. __________________ sympathy, empathy and apathy... i dont know which one is which.... But i know you can find sympathy between shit and syphilis in the dictionary. Win this car for a whole BUCK!

08-19-2009, 07:13 AM	#5 (permalink)
rcurrier44 Registered User Join Date: Dec 2002 Member # 15404 Location: Hillsboro, OR Posts: 3,080	Is your shaft powered or just spinning? Many front drive shafts will slowly spin because of the fluid movement in the t-case from other gears spinning. __________________ Life begins where the pavement ends!

08-19-2009, 01:42 PM	#11 (permalink)
smokewrench Registered User Join Date: Feb 2009 Member # 130142 Location: new hampshire Posts: 67	Might be out of adjustment, its not to hard to adjust. I had a similar problem in a truck with a body lift, when in 4L-loc it was hitting the floor. I made the hole a little longer. __________________ 76 k-10 stepside 44/14 d60 going under soon 305 h.o huge cam roller rockers and megasquirt sm465/205

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08-19-2009, 05:32 AM	#3 (permalink)
cur_dog Wheeler Join Date: May 2008 Member # 113958 Location: Houston, TX Posts: 185	I thought (newbie) that if it did not have the part time kit in it and the hubs were not locked that it would not work at all. Again, I thought (newbie) that without the part time kit in it that the rear output needed resistance from the front output to work. Probably not making sense here but maybe someone will understand what I'm trying to say.

08-19-2009, 06:12 AM	#4 (permalink)
cur_dog Wheeler Join Date: May 2008 Member # 113958 Location: Houston, TX Posts: 185	I found this. This might explain it better. The full-time aspect of the 203 is all in the rear section of the unit. The case has an internal differential that selectively splits the power to the front and rear axles when the shifter is not in one of the locked positions. When shifted into Hi-Loc or Lo-Loc, the differential locks to provide equal power to both driveshafts. If you removed either driveshaft and tried to drive the truck with the case in the nonlocked position, the internal diff would send all the power to the yoke with the missing shaft. It’s just like an open rear axle differential, where all the power goes to the tire with the least traction. However, if the case was shifted into a locked position, power would be equally distributed to the front and rear, so you’d be able to drive the rig as long as one driveshaft was still in place.

08-19-2009, 08:09 AM	#6 (permalink)
cur_dog Wheeler Join Date: May 2008 Member # 113958 Location: Houston, TX Posts: 185	It's powered

08-19-2009, 08:11 AM	#7 (permalink)
KWTMECH Registered User Join Date: Sep 2002 Member # 13786 Location: moved 7 miles to colfax, ca. Posts: 4,224	See above post number 2

08-19-2009, 08:29 AM	#9 (permalink)
cur_dog Wheeler Join Date: May 2008 Member # 113958 Location: Houston, TX Posts: 185	That is correct.

08-19-2009, 11:56 AM	#10 (permalink)
Cubman Registered User Join Date: Sep 2007 Member # 100204 Location: Cookeville, TN / Oak Ridge Posts: 40	I have a '78 K10 with the 400/350/203 and hubs on the front axle. I have the same problem as cur_dog. When in 4H (unlocked) the front driveshaft is still driven. The t-case will go into 4H-Loc, but will pop out after a few seconds. I don't know if the shifter is out of adjustment or if there is something that is binding when it is locked. Is it safe to bungee cord the t-case shifter in the 4H-Loc position?