The 1947 - Present Chevrolet & GMC Truck Message Board Network

The 1947 - Present Chevrolet & GMC Truck Message Board Network (
-   The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board (
-   -   78 NP203 oil change question (

teamssc 07-29-2012 04:29 PM

78 NP203 oil change question
I've only had this truck a few months and it runs great. I'm trying to work my way through the fluid changes and want to change the fluid in the NP203 but I can't find have gaskets to put the covers back on. Where can I find the two gaskets I need? I've found whole rebuild kits for $25 or so, which I don't mind spending, but I only need the 2 gaskets. I guess I can always drain the fluid now and do the gaskets later. With 5 qts of 10w30 just running $15 it's no big deal to do it now and later.

Lobie 07-29-2012 05:38 PM

Re: 78 NP203 oil change question
Try here
Posted via Mobile Device

teamssc 07-29-2012 05:55 PM

Re: 78 NP203 oil change question

Originally Posted by Lobie (Post 5511791)

Thanks, I've looked at those diagrams before and I'm not seeing the external cover gaskets. Actually I'm not seeing the covers in those diagrams at all.

teamssc 07-29-2012 06:17 PM

Re: 78 NP203 oil change question
The rear cover you take off might be called a Housing to Chain Cover Gasket. Not sure

NP 203, Housing to Chain Cover Gasket, Code: 301306
Industry Ref # D4TZ-7086C

teamssc 07-29-2012 06:37 PM

Re: 78 NP203 oil change question
Here's the 301306 gasket. Doesn't look the right shape.

Here's a link to a picture of my transfer case. What I need is the gasket to the right. There is also a rectangular gasket on the left side lower that can't bee seen in this picture. (also if someone determines this is not an NP203 please tell me.)

teamssc 08-01-2012 05:44 AM

Re: 78 NP203 oil change question
Bueller?... Bueller?... Bueller?

This still isn't resolved. Is there anyone who can offer some more help?

bilfman 08-01-2012 10:33 PM

Re: 78 NP203 oil change question
Just clean off the surfaces well with a wire brush, wipe clean with some brake cleaner and seal up with a healthy bead of silicone. I like permatex ultra grey.

Smart move on the 10-30 lotsa peeps put in gear oil in the 203 and burn em up. I prefer plain 30 over the 10-30.

Also a great tip if you have converted the 203 to a part time. There is oiling issues because the 203 is designed to be spun fulltime. So if converted to part time engaging it every 100 miles or so was the answer. I had an ol guy at a tranny shop tell me a tip that eliminates the need to engage the t case or hubs. Just get a 1/2" 90 elbow, a 1/2" 2" nipple and a cap. Extend the fill hole 2 inches higher with the elbow and nipple and then cap after you fill the case. Basically this just fills the case with about another 2 1/2" of oil and it keeps everything lubed without having to engage the case. I did this on mine and never had an issue.

teamssc 08-02-2012 12:59 AM

Re: 78 NP203 oil change question
Bifman, that's exactly what i needed to hear, using the permetex and the nipple idea. Since my 203 has been converted the extra oil will surley extend it's life. I'd heard about the nipple before and forgot it. It will be good to get inside the case and check it out. I might need a chain so this way I'll have some piece of mind.

Many thanks!
Posted via Mobile Device

All times are GMT -4. The time now is 12:17 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.
Copyright 1997-2013