Author Topic: np203 ?  (Read 16788 times)

Offline 76bonanza68

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np203 ?
« on: February 23, 2003, 03:07:00 PM »
I am new to the 4x4 boards just got rid of a 2000 ford lighting for a 76 k10.

I have a 203 t-case that has been changed to part time.  It seems to be leaking out of what looks like a weep hole on passangers side by front output shaft?  Also it appears he has been running transmission fluid in it I was going to drain it and put in 10w40, But I can not find drain plug found fill plug(I know i am an idiot)"  One more question the breather valve is gone just hole in top of rear output cone can I get this piece at local parts store and just push in hole?

Thanks for any help hope to enjoy this board for some time.


Offline oscarone

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np203 ?
« Reply #1 on: February 23, 2003, 10:09:00 PM »
There is no drain plug.  Pull a bolt from the bottom of the case.  They are drilled thru.  As far as the vent, I think it is a threaded fitting.  And of course, get the tranny fluid out of it.  It will kill it.  10w-40 is what it needs.


Offline 76bonanza68

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np203
« Reply #2 on: February 24, 2003, 05:13:00 PM »
how many quarts if i drain and refill and will it be ok mixed because i am sure all the tranny fluid will not drain?


Offline oscarone

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np203 ?
« Reply #3 on: February 24, 2003, 09:44:00 PM »
I think the 203 holds about 4 quarts.  Fill it the same way you would an axle.  Until it spills from the fill plug.  I it were me, I would drain the tranny fluid,  fill it with oil and take a few miles drive.  Then drain and fill it again.  This would help to flush it out.  Another bit of advice.  The 203 requires the chain be driven to splash oil into the tail housing.  When it is converted to part time the doesn't happen.  There is a pump up there that will burn up.  Once a week lock your hubs for the drive to work.  This will throw some oil into the tail housing.  You don't need to put the case in 4wd, just lock the hubs.  The axle/prop shaft will drive the chain.


Offline johnhardaway

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np203
« Reply #4 on: June 29, 2003, 09:46:00 PM »
Go back and beat the heck out of the guy that filled it with tranny fluid.  The old notorious used car dealers used to use this trick in engines to clean out the sludge and gunk.  This made it look good, but the crap that it broke loose would usually damage the engine.
My advice, overhaul the case and refill it with full-synthetic engine oil.


Offline 77bowtie

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Re: np203
« Reply #5 on: December 06, 2003, 09:50:00 AM »
I can't help but wonder. Am I the only one that runs gear lubricant, SAE 75w-90 in a 203 transfercase?


Offline oscarone

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Re: np203
« Reply #6 on: December 06, 2003, 12:30:00 PM »
No...I don't think your the only one, but, it is not the right fluid.  10w30 or 40 is the correct oil.  The 203 depends on the chain "splashing" fluid into the tail housing.  The gear oil is too thick for this and tranny fluid is too thin too "stick".  I would drain it and put in the 10w30/40.  Are you running a part time conversion?  
I was just thinking...a lot of people don't like the 203.  It is suppose to be the weaker of the t-cases.  Because it is chain driven.  I think a lot of the problems are from using the wrong fluid.  And, if you have a part time conversion you need to lock the hubs once a week and let the chain splash some oil arround.  Anyway, it seems the 203 holds up pretty well considering how many people use the wrong fluids.
I have the 203 in my 77 k10.  I have a 383 that puts out a heck of a lot of torque in low range, and, have never had a problem with it.  I do want to change it, though.  I want a "double pumper" from offroad design.  Don't think santa will drop that down the chimney...along with some dynatrack axles....


Offline 77bowtie

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Re: np203
« Reply #7 on: December 18, 2003, 08:28:00 AM »
I know the reason I'm using "the wrong lube" is that, thats whats called for in the 77 truck service manual from Chevy! No-wonder-why?


Offline oscarone

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np203?
« Reply #8 on: December 18, 2003, 07:58:00 PM »
Really?  Where at in your manual?  I just checked mine for the heck of it.  '77 light duty service manual page       0B-17 calls for engine oil in the full time case.


Offline 77bowtie

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Re: np203?
« Reply #9 on: December 20, 2003, 07:31:00 AM »
Ok I stand corrected! Your right about page ob-17! The wrong info is in the Chilton's manual's. No-matter though! Not only has my np-203 been changed over to part-time, I've removed the tc completly. Thanks for the correction...Jon