Another NP203 or NP205 thread

[K-10beast]

here's the rub...I can't find an answer on which it could be since it seems to fit both model's descriptions.  I want to change the oil/gear oil in it and don't want to put the wrong goo inside.  Truck is fairly new to me and I'm finding lots of stuff that came from other places!

1977 K10 350 TH400

ID plate long gone on the T-case (?)
Speedometer cable on Passenger side (205?)
no 3 bolt inspection cover on rear side (203?)
input on passenger side (205?)
shifter is not OEM and doesn't have any markings for hi/low etc. (?)
manual hubs (205?)
shift levers feed into a square block looking thing (203?)

Thanks!

[rich weyand]

Post a pic from the rear.

[K-10beast]

here ya go.  Yep, I have a leak

[rich weyand]

That's an NP203 where the main output shaft cone has been put on upside down to exit the speedo cable to the passenger side.

Straight-weight 30W engine oil is the correct lubricant.

Note that if that is a modded NP203 and you have locking hubs (rather than slugs), and you drive around with the hubs unlocked, you must lock the transfer case once in a while to throw oil up inside the case so it can run down the internal rails into the oil reservoir at the main output shaft bearing.  If you do not do this, you will end up running that bearing dry and eating it up.  I lock the transfer case for the first mile or two I drive every day, then unlock it for the rest of the day.  If on a long trip, lock it for a mile or two every time you start out after stopping for gas or a rest stop.  Note that, with the hubs unlocked, you can only lock the transfer case when stopped, but you can unlock it when moving.

[K-10beast]

Thank you very much!  That makes a whole lot of sense and I didn't know about locking it up once a day.  I'll do that every morning from now on and hopefully it will last as long as the last 203 I had.

Thanks Again!

[Irish_Alley]

dont think locking it up every day is a bad thing just never heard of anyone saying to do it that often. i always thought once a month

[rich weyand]

I only do it for a mile or so.  The problem with doing it once a month is remembering to do it.  I lock it up as I head down the driveway, then unlock it when I get to the state highway a mile or so down the lane.  Easy to remember.

[Irish_Alley]

if i was to do it it would have to be done right after a oil change on that type of scheduled. know a guy who has a bunch of vehicles in his garage. but he parks his dd all the way in the back so everyday he has to start and run each of the vehicles just to drive his truck. kind of over kill but just like you at least he knows hes doing it