NP203 Oil Change

[1975 K20]

I have a 1977 K20 with the NP203. I have changed the oil in NP205's before with no trouble, but I went to change it in the NP203, and there was no visible drain port. How do I go about draining it? Thanks!

 

[legopnuematic]

It should be able to drain from one of the bottom cover bolts on the back of the case.

 

[1975 K20]

So I can just take out one of the bolts on the rear of the t-case, and it will drain, and then I just put the bolt back in, and don't have to replace the seal?

 

[idahovette]

yep done it many times on my 75 K20. Used to do it every time I changed the engine oil and used the same oil as the engine...(worked at the Chevy garage, was cheap)

 

[1975 K20]

Thanks!

 

[75gmck25]

That is definitely how your drain an NP203. Then fill with 30 weight oil until it dribbles out the fill port. Some guys tilt the truck on ramps and try to get a little extra oil in to help lubricate the chain, but I’ve never tried it.

If it’s a converted NP203 you are supposed to run it in 4WD about once a month to ensure full circulation of oil, but I’m sure most guys forgot those directions about a week after they installed the part-time kit.

 

[idahovette]

My part time conversion kit had an elbow to put in the fill hole, effectively raising the full level? Maybe a pint?

 

[1975 K20]

Thanks!

 

[WFarm]

Drain bolt circled below.

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[1975 K20]

Can you drain it out of both bottom bolts?

 

[WFarm]

Not sure, never tried.

 

[1975 K20]

Ok. I was just making sure I didn't wreck anything because I pulled out both.