Full Size K5 (1969-1991) GMT415 (1992-1994) Tech Discuss any and all full size K5 general tech topics here.

1977 k5 blazer 4x4 issue

  #1  
Old 02-11-2019, 05:56 PM
New Member
Thread Starter
Join Date: Feb 2019
Posts: 3
Tony DeGroote is on a distinguished road
Default 1977 k5 blazer 4x4 issue

Hey guys i recently bought a 77 K5 Blazer I'm having an issue shifting into 4 x 4 the shifter will go to neutral or what I think is 4 high the plate on the shifter has L lock L N H H lock I can only get it to go into neutral or back one click it has what I assume are the factory Auto locking hubs if that matters if anyone had any suggestions on where to start looking thank you in advance
 

Last edited by Tony DeGroote; 02-11-2019 at 05:58 PM. Reason: More info
  #2  
Old 02-11-2019, 09:01 PM
swartlkk's Avatar
Administrator
Join Date: May 2005
Location: Waterloo, NY
Posts: 40,792
swartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond repute
Default

You have the NP203 transfer case based on your comment about Lo/Hi and Loc positions. I am going to go out on a limb and state that you also have lockout hubs on the front axle.

The NP203 is a fulltime 4wd transfer case that has a center differential to allow for different driveshaft speeds necessary during tight turning on high traction surfaces. From the factory, the hubs have splined pucks that keep the wheels engaged at all times which is required for the Lo & Hi shifter positions where the center differential is open. If either hub is unlocked when in the Lo or Hi positions, the truck won't go anywhere. In either of the Loc positions, the center differential is locked and equal power is sent to both axles and it doesn't matter if one of the hubs is unlocked as the rear axle will still get power.

My '74 currently has the NP203 and lockout hubs, but my 203 has been modified with a part-time conversion which always sends power to the rear output, regardless of shifter position. Milemarker used to make a kit. I'm not sure what is still available.
 
  #3  
Old 02-12-2019, 01:57 AM
New Member
Thread Starter
Join Date: Feb 2019
Posts: 3
Tony DeGroote is on a distinguished road
Default

It does not have manual lockin hubs on it there is,no selector on them. As for the transfer case is,there a way to tell what type,of transfer case that i have on,it? And i gues my problem so far is that the shifter itself wont go into all 5 positions (I think its 5) only 2 .
 
  #4  
Old 02-12-2019, 06:41 AM
swartlkk's Avatar
Administrator
Join Date: May 2005
Location: Waterloo, NY
Posts: 40,792
swartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond reputeswartlkk has a reputation beyond repute
Default

If you do not have lockouts on the front axle, then it is possibly an issue with the shifter not placing the transfer case in the proper selection. It could also be possible that there is something wrong in either the front or rear driveline, but based on your comments about not being able to shift into all of the positions on the transfer case, I would start with the shifter on the transfer case.

The NP203 transfer case is quite simple in operation. There are only two controls for it. One linkage connects to the range box which is the front most section of the transfer case. It handles the gear ratio selection (Hi, Lo, or N). The second linkage connects to the rear section of the transfer case and is responsible for the Loc function of the center differential. What it sounds like is happening is that a section of your shift linkage is bound up and not properly.

There are many good walkthroughs on how to disassemble & clean the NP203 shifter online. When I did mine, I had a spare that I was able to take apart then just swap it into the truck. Sadly, I didn't take any pictures, but THIS THREAD on 73-87chevytrucks.com goes through the process quite thoroughly. Some have had success dousing the shifter box with a light oil and moving it until it frees up. One other thing to note is that the gears may not always line up properly in both the range box and the differential which can make the shifter not want to move very well either. I find it easiest to be slightly rolling with my K5 for both locking the transfer case as well as range shifts. Always have the transmission in neutral when attempting range shifts with this transfer case.
 
  #5  
Old 02-12-2019, 09:17 PM
New Member
Thread Starter
Join Date: Feb 2019
Posts: 3
Tony DeGroote is on a distinguished road
Default

Originally Posted by swartlkk View Post
If you do not have lockouts on the front axle, then it is possibly an issue with the shifter not placing the transfer case in the proper selection. It could also be possible that there is something wrong in either the front or rear driveline, but based on your comments about not being able to shift into all of the positions on the transfer case, I would start with the shifter on the transfer case.

The NP203 transfer case is quite simple in operation. There are only two controls for it. One linkage connects to the range box which is the front most section of the transfer case. It handles the gear ratio selection (Hi, Lo, or N). The second linkage connects to the rear section of the transfer case and is responsible for the Loc function of the center differential. What it sounds like is happening is that a section of your shift linkage is bound up and not properly.

There are many good walkthroughs on how to disassemble & clean the NP203 shifter online. When I did mine, I had a spare that I was able to take apart then just swap it into the truck. Sadly, I didn't take any pictures, but THIS THREAD on 73-87chevytrucks.com goes through the process quite thoroughly. Some have had success dousing the shifter box with a light oil and moving it until it frees up. One other thing to note is that the gears may not always line up properly in both the range box and the differential which can make the shifter not want to move very well either. I find it easiest to be slightly rolling with my K5 for both locking the transfer case as well as range shifts. Always have the transmission in neutral when attempting range shifts with this transfer case.


Allright! I will give that a shot! I appreciate the help.
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
icehawk89
Full Size K5 (1969-1991) GMT415 (1992-1994) Tech
2
08-02-2009 08:03 PM
Quicksilver
General Chat
7
10-25-2008 04:33 PM
Benzin
Engine & Transmission
3
07-30-2008 06:15 AM
shauna8378
General Chat
6
07-28-2008 03:26 PM
orange drop
Full Size K5 (1969-1991) GMT415 (1992-1994) Tech
2
12-07-2007 07:25 AM


Thread Tools
Search this Thread
Quick Reply: 1977 k5 blazer 4x4 issue


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.