Author Topic: 78 Chevy K10 Transfer Case Question  (Read 1456 times)

Offline guroojedi

  • Newbie
  • Posts: 4
  • Newbie
78 Chevy K10 Transfer Case Question
« on: October 04, 2018, 12:58:21 PM »
My son and I bought this truck to fix up and drive (functional and pretty).

According to the VIN it had a 400 engine in it, but we were told it was swapped to a 350 engine before we bought it. He didn't say if he swapped the tranny and T-Case also.

The 4x shifter is stuck in (what looks like) 4H. I think a rebuild or replace is in order but not sure if it's a 203 or 205.

It looks like 203 but that lower right plug seems out of place ....
78 Chevy K10
79 Harley Sportster
06 GMC 2500 HD

Offline Rapid Roy

  • Junior Member
  • ***
  • Posts: 568
  • Euless, Texas
Re: 78 Chevy K10 Transfer Case Question
« Reply #1 on: October 04, 2018, 01:33:20 PM »
Welcome
1974 Cheyenne 10 LWB 350/TH350/AC/4 BBL Quadrajet
Mopar by Birth
Chevy by Choice

Offline guroojedi

  • Newbie
  • Posts: 4
  • Newbie
Re: 78 Chevy K10 Transfer Case Question
« Reply #2 on: October 04, 2018, 03:06:04 PM »
Thank you
78 Chevy K10
79 Harley Sportster
06 GMC 2500 HD

Offline Captain Swampy

  • Junior Member
  • ***
  • Posts: 504
  • Wisconsin
Re: 78 Chevy K10 Transfer Case Question
« Reply #3 on: October 04, 2018, 04:29:53 PM »
The 203 is full time 4x4. The shifter would say Hi loc, Hi, N, Low, Low loc. The one in the picture doesn't look like a 203.
1987  350TBI 700R4  4X4  4.56 gears  33" BFG All Terrain


http://forum.73-87chevytrucks.com/smforum/index.php?topic=32209.0

Offline guroojedi

  • Newbie
  • Posts: 4
  • Newbie
Re: 78 Chevy K10 Transfer Case Question
« Reply #4 on: October 04, 2018, 04:32:05 PM »
It does say Hi loc, Hi,N, Low, Low Loc

Any idea what it may be?
78 Chevy K10
79 Harley Sportster
06 GMC 2500 HD

Offline Captain Swampy

  • Junior Member
  • ***
  • Posts: 504
  • Wisconsin
Re: 78 Chevy K10 Transfer Case Question
« Reply #5 on: October 04, 2018, 04:39:59 PM »
Actually I think it is a 203. There is a set of spider gears in the rear housing. It locks them in the loc positions so the front and rear drive shafts have to turn. Another thing is from the factory they just had covers over the front spindles as they didn't use locking hubs.
1987  350TBI 700R4  4X4  4.56 gears  33" BFG All Terrain


http://forum.73-87chevytrucks.com/smforum/index.php?topic=32209.0

Offline Captain Swampy

  • Junior Member
  • ***
  • Posts: 504
  • Wisconsin
1987  350TBI 700R4  4X4  4.56 gears  33" BFG All Terrain


http://forum.73-87chevytrucks.com/smforum/index.php?topic=32209.0

Online ehjorten

  • Senior Member
  • ****
  • Posts: 1062
Re: 78 Chevy K10 Transfer Case Question
« Reply #7 on: October 04, 2018, 05:01:54 PM »
That is a NP203.  It is a full-time 4wd transfer case.  From the factory they did not have selectable hubs.  Many were converted to part-time 4wd to save on front-end wear.  In that case there is a kit that goes in the back of the case to lock-out the center differential.  You then put on selectable hubs on the front.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline 75gmck25

  • Frequent Member
  • **
  • Posts: 423
  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: 78 Chevy K10 Transfer Case Question
« Reply #8 on: October 04, 2018, 07:44:55 PM »
If there are fixed hubs on the front axles, its probably an uncoverted NP203.  In stock form (no conversion) they are very reliable, but boxes converted to part time may not have been maintained properly to ensure the internal pump circulates oil.

There are several sites out there that explain how to adjust the shift linkage on the NP203.  Mine has always worked fine, but it seems like many folks have trouble with the linkage.

Bruce

 


Offline Irish_Alley

  • Tim
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13270
  • Family is not an important thing. It's everything.
Re: 78 Chevy K10 Transfer Case Question
« Reply #9 on: October 05, 2018, 07:25:56 AM »
cant disagree only add to whats been said. 203s have no "drain plug" unlike the 205, to drain a 203 you remove the lower two bolts in the cover on the lower right side. that plug on the right side isnt really a plug but support bracket that should go to the bell housing. if you remove the trans for whatever reason put the bracket back in place.

if you also notice there seams to be a box in the lower left side of the T-case thats actually because the Np203 is a two piece setup unlike the 205. some people will take the front gear box and attached it to a 205 to make the "doubler"  for a 4:1 low range
 

unless you plan on rock crawling dont waste your time or money on it.

about the handle being stuck, jack the truck up and try to rotate the tires sometimes the hubs will get stuck and even with manual hub they'll stay in 4x4 and will bind up the transfer case making it almost impossible to remove out of gear. 
If you canít tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline guroojedi

  • Newbie
  • Posts: 4
  • Newbie
Re: 78 Chevy K10 Transfer Case Question
« Reply #10 on: October 05, 2018, 10:04:12 AM »
Thank you everybody - very good info here
78 Chevy K10
79 Harley Sportster
06 GMC 2500 HD

Online JohnnyPopper

  • Site Supporters
  • Junior Member
  • ******
  • Posts: 945
  • Old Goof
Re: 78 Chevy K10 Transfer Case Question
« Reply #11 on: October 05, 2018, 02:07:50 PM »
Welcome from another newbie!

Miles Marker makes the conversion kit. I think they still make the front locking hubs.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction