1977 K20 Drain Transfer case Plug

[bucket]

Thanks, I will drain out the gear oil and replace it with 10-40 and run it while I break in the motor and change it again when I change out the break-in oil.
How do you determine the difference between a full tine and part time transfer case.
Thanks, again

To tell if a 203 has been converted, unlock the front hubs, put the shifter in HI (not HI LOC) and drive. If the truck does not move, the case has not been converted to part time.

 

[Bextreme04]

To tell if a 203 has been converted, unlock the front hubs, put the shifter in HI (not HI LOC) and drive. If the truck does not move, the case has not been converted to part time.

That will tell you functionally if it is part time or full time, but for the original question of how to tell whether you have what the manual is describing... It is talking about a NP203(full-time) or NP205(part-time). The NP203 is chain drive and will need 10w30 regardless of whether it has been converted to part-time or not. An NP205 is gear drive and will need 80w90. You can tell which one you have easily from the gear shift knob. NP203 shift knob will have LO;LO*LOC;N;HI;HI*LOC on the shifter. NP205 will only have 4L;N;2H;4H on the shift knob. There are a few visual cues and other ways to tell from just looking at the case itself, but looking at the shift knob is definitely the quickest and easiest way to tell once it's installed in the truck.

 

[bucket]

That will tell you functionally if it is part time or full time, but for the original question of how to tell whether you have what the manual is describing... It is talking about a NP203(full-time) or NP205(part-time). The NP203 is chain drive and will need 10w30 regardless of whether it has been converted to part-time or not. An NP205 is gear drive and will need 80w90. You can tell which one you have easily from the gear shift knob. NP203 shift knob will have LO;LO*LOC;N;HI;HI*LOC on the shifter. NP205 will only have 4L;N;2H;4H on the shift knob. There are a few visual cues and other ways to tell from just looking at the case itself, but looking at the shift knob is definitely the quickest and easiest way to tell once it's installed in the truck.

Oh, I didn't realize that was a question anymore. The case pictured by the OP is a 203 for sure.

 

[Bextreme04]

Oh, I didn't realize that was a question anymore. The case pictured by the OP is a 203 for sure.

Sorry, I was responding to this quote

Thanks, I will drain out the gear oil and replace it with 10-40 and run it while I break in the motor and change it again when I change out the break-in oil.
How do you determine the difference between a full tine and part time transfer case.
Thanks, again

I thought what he was asking was in relation to the owners manual. He knows his truck has an NP203, but not that having an NP203 means he needs to follow the guidance in the owners manual for full-time 4wd regardless of the status of the locking hubs or part-time conversion. Since the manuals and literature only refers to "part-time" and full-time" 4wd, but never mentions transfer case models, I was just trying to connect those dots for the OP and anyone else that might come across this thread in the future.

 

[highdesertrange]

lets see if I remember how to do this,

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hey that was easy. right there in the circle, that is the idler shaft rear plate. that is a 205 part time transfer case. that is the quickest easiest way to tell.

highdesertranger

 

[75gmck25]

It sounds like you have an NP203 full time case that has been converted to part time and locking hubs. That was a common “fix” in an attempt to improve gas mileage with the full-time/AWD transfer case.

There is an oil circulation pump in the NP203, and after the conversion you are supposed to put it in 4WD with the hubs locked about once a month so that it fully circulates oil in the transfer case and lubricates the chain.

My vent fitting also pulled out, so I just cleaned it up and used JB weld to keep it in. It’s been like that for about 15 years, so it seems to hold fine.

Bruce

 

[Big red square]

It sounds like you have an NP203 full time case that has been converted to part time and locking hubs. That was a common “fix” in an attempt to improve gas mileage with the full-time/AWD transfer case.

There is an oil circulation pump in the NP203, and after the conversion you are supposed to put it in 4WD with the hubs locked about once a month so that it fully circulates oil in the transfer case and lubricates the chain.

My vent fitting also pulled out, so I just cleaned it up and used JB weld to keep it in. It’s been like that for about 15 years, so it seems to hold fine.

Bruce

You put it in Hi loc once a month?

 

[75gmck25]

My 203 is still full time (factory original) so I just check the oil periodically (I used synthetic 10w30).

Only the 203 cases that have been converted to part time need to be put in hi-loc every month or so to fully lubricate them.