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NP203? 1978 blazer problems and questions

J

JACKBURTON55

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I have a 78 K5, it has a few issues but the one troubling me most right now is the transfer case, it shifts out of 2H occasionally and then to get it back into 2h you have to put it in neutral and shut the truck off. This cant be normal. What does this sound like? its not the transmission, it shifts great. Also, all the way down(toward the back of the truck) is 2H, then Neutral, then 4H and then 4L
 
On an NP203 you have to be stopped, trans in neutral, then shift t-case into gear, then shift trans back into gear.

It's been too long since i've owned a rig with a 203 in it so i can't remember the order but there is a low, low-lock, nuetral, high, high-lock. There is no 2wd since a 203 in stock form is a fulltime 4wd case.
 
well i didn't think i had a 203, but according to the specs on the main page thats what i have. I have manual warn locking hubs on there, it had autos on there i believe because the previous owner gave me a box with some rusty autos in it
 
Auto hubs NEVER came on a rig with an NP203 t-case. If you have a 203 case AND have manual locking hubs then someone has put a part time kit into the t-case.
 
It may be a 203 that's converted to part time. I doubt it's a 205 because they're usually hard to shift, let alone pop out of range and into nuetral. 203's did have an issue with popping into nuetral.

I have a pic of a 203 range box, it's the front part of a 203 tranfer case and this pic shows a small lever for the shift arm.

111aaa002.jpg


Directly below that arm is a large flat hex nut (you can just see the edge of the hex in that pic, and the hex is clearly visible if you're looking up at it from underneath). If you remove that nut you'll find a spring under there which is for the detent mechanism. The spring gets weak with age and doesn't allow the detent to be firm enough to prevent the case from popping into nuetral. If I recall correctly it would usually do it as soon as you let off the gas...

i added a thick washer under that spring and the shifting was firmer from range to range, and it didn't pop into nuetral anymore.

Rene
 
I was thinking about it, I checked the center console and i do have an extra shift nob for the T-case that has hi loc hi n lo lo loc. on it. so it must have had the conversion done. Ill have to get under there tomorrow and see if i can see the lever and possibly do that washer mod
 
ok guys, I am very confused by my truck. Its not that im not used to transfer cases but this is my first chevy and the only other 2 trucks I have driven offroad are a 99 Dodge ram 2500 and a 95 isuzu trooper.

Check this out, cant be a np203





off topic, good oil pressure?
 
The sun visor doesn't really mean anything since it could have come another 4x4 chevy.
Pics of the transfer case will get you the answer your looking for.
 
you probably have a np208 from the looks of the picture of the shifter on the floorboard...

here is a backside pic of a np203:

7950010017_medium.jpg
 
That shifter is ONLY used with the NP208 and NP241 t-cases.

The hood is 1980? and earlier, the passenger side seat mount is mid 80's-later. Seems like it's anyones guess as to what someone might have installed in this rig with so much not being year correct for a 78 blazer.
 
looks like i have a np203 then







the shifter is just weird though, it seems to me that all the way back on my shifter is 2 or 4 high and then it sometimes pops just a little forward and is in neutral.
 
With a part time conversion the shift pattern is as follows:
dash
-
4lo
-
2lo
-
N
-
2h
-
4h
-
console
​
Try adjusting the shift linkages and see where that gets you.
 
The shifter is wrong for a 203 t-case and is why you're having issues. The shifter you currently have only has 1 shift rod and the shifter for an NP203 requires 2 shift rods that work independently of each other.
 
also look like you are missing the tcase to tranny support rod that started to come on the 78s. Prior was the tcase to frame mount. You need that support or risk cracking the tranny
 
4X4HIGH said:
The shifter is wrong for a 203 t-case and is why you're having issues. The shifter you currently have only has 1 shift rod and the shifter for an NP203 requires 2 shift rods that work independently of each other.
Click to expand...


crap in a blue dish, do you have a picture of this and what its supposed to look like? what happened to my truck? I figured the shifter is wrong . . i have a knob for a full time 4x4 and it doesnt fit my shifter
 
wazzabie said:
also look like you are missing the tcase to tranny support rod that started to come on the 78s. Prior was the tcase to frame mount. You need that support or risk cracking the tranny
Click to expand...


scary, where would this be located? I would go about sourcing one asap, any pics?
 
JACKBURTON55 said:
crap in a blue dish, do you have a picture of this and what its supposed to look like? what happened to my truck? I figured the shifter is wrong . . i have a knob for a full time 4x4 and it doesnt fit my shifter
Click to expand...

I can't find an image of a stock np203 shifter however i did find a pic of one that someone modified for twin stick which will look the same except for only having one shift lever. Here is what one would look like. You might want to take a pic from underneath your rig of the shifter area so we can see what's going on there.

203 shifter.gif
 
If your np203 is still full time and you have locking/unlocking hubs, with the hubs unlocked, your pattern will be this: Console to dash Hi lock, neutral, Lo lock. You lose the unlocked modes because there is an open diff inside the case so you have to be in either one of the lock modes to get power to the rear axle. If you lock your front hubs, you can put the case in unlocked modes and its full time 4x4 but it differentiates power front to rear.
 
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