98 K1500 manual trans--no 4x4

[Bryan59EC]

Some time ago--two years maybe, I had to replace the transfer case on my pickup.

All was good until about 2 months ago when I needed the 4x4 it did not work.

Changed the actuator and it worked just fine----once

Fast forward to today -- again---no 4x4 engagement

Fuse good----cannot hear actuator with key on and going thru the ranges

Change TC switch---no change

plug wiring into removed switch and the actuator engages (I think)

Remove actuator plug harness to actuator key on
depress TC switch and actuator retracts----release and the actuator extends.

replace actuator----plug TC into loose switch actuator makes noise.
Start truck put into 4-lo and go out to my yard to try to climb a some sand.

Bury the truck-----the ranges seem to be working but I really have no way
of seeing if the transfer case is actually engaging the front driveshaft.

Is it possible that some shifting mechanism has broken inside the TC.

Sticking my finger inside the TC switch hole, it feels like the pawl is a bit off center----I did not think to see if it actually moved out of the way when in 4wd.

Or did something wig out in the differential---not sure.

Any ideas???

[andrewmp6]

You could pull the rear driveshaft shift it in to 4 wheel low or high and see if the truck will pull at all.Or put it on 4 jack stands and shift it in 4 wheel and see if the front wheels turn or not.

[Bigdav160]

Push button or lever?

[special-K]

Looks like button switch. I guess it's possible your TC has a problem, but I suspect a connection or other. Need to wrap my head around it a while.

[Bryan59EC]

all manual

big levers sticking out of the floor for both the trans and the transfer case.

[Ol Blue K20]

What about the front diff actuator? I've replace mine twice. The transfer went into 4wd but the front diff didn't lock in.

[Bryan59EC]

Actuator has been in there less than a month --- and it does function when I remove the switch from the TC and work it manually (actuator out of axle).

But something dawned on me just recently-----seems all the drawings I see of the TC/Acuator circuit have a relay somewhere----I have no idea where it would be or even if the manual trans/manual transfercase vehicles even have one.

No time to play with it last week or even this upcoming week as it needs to drivable to the airport (where it pretty much lives)

Should be working in my hometown after the 8th for a few days so I might get somewhere with it.

Would really like to--the brush piles need to be consolidated into a single pile for burning and I ain't about to go back there again without the 4x4 working.

[Bryan59EC]

UPDATE:

Lost job after 37 years
Had to put a new engine in the truck----190,000 pasture miles (it was due as oil pressure dropped to zero at idle and had been knocking for a couple of years now)

Started new job and have had little time to mess with it.

Just picked up the truck today after getting engine installed and put it up on a rack.

Removed the actuator and fired the truck up---put in 4-low and and let it idle.


Front driveshaft is turning and it is positive, not just floating with the t/c.

Floor indicator not coming on and actuator not engaged (plugged in hanging)

Insert an extension bar into the front end and the differential engages just fine.

Unplug actuator switch and plug a loose switch to the harness

Actuator starts dancing at the end of it's harness like it is trying to engage.

Plug harness back to t/c and play with wiring over the top of the t/c and the actuator starts dancing again.

This kind of tells me that there is a bad wire somewhere in the harness.

Now, I have looked for a STANDARD wiring diagram for this truck and cannot locate one anywhere.

Manual 5spd with a NP241C t/c
The only electrical connections on this t/c are for:
VSS
Differential actuator

Does anyone have an electrical diagram that will show the wiring of a BASE
5-spd 4x4----no dash switches, no dash indicators--the only indicator is a lamp on the floor shifter that lights when it is placed in either of the 4x4 positions.
This lamp has stopped working as well---was working earlier in the summer.

The only diagrams that I can find are for the trucks with the buttons on the dash and automatic transmissions---my truck has neither.

If this thing has relays or modules, I have no idea where they may be located. Still kind of anxious to get the 4x4 working, especially now that I know it is not mechanical.

The good news is that my truck no longer rattles at a light and the oil pressure is staying at 40+ all the time.

[Bryan59EC]

Nobody??

[1976gmc20]

Originally Posted by Bryan59EC

Nobody??

Sorry, late to the party. Haven't been on the forum a couple years.

My $0.02:

FORGET the damn actuator. Pull the fuse or leave it unplugged. Cut a piece of 3/4" PVC about 1 1/8" long, and it will stick right on the end of the actuator. Bolt the actuator back into the axle (might need to jack up right front wheel and rotate it a bit to let the differential lock together as you tighten down the actuator).

I did this to my 1989 about five years ago. Doesn't hurt anything for the CAD to be locked in "permanently." Some other vehicles work this way like most of the Jeep XJs (early ones had CAD and most jeepers "delete" them).