4wd not locking in

[ccc]

Anyone have any insight on why my 4wd isn't locking in? I have a 1997 K15oo, 6.5td auto with push button 4wd. I thought the front diff actuator quit so I bought one at O'Reilly and put it in today but it appears that isn't the problem. When I push the button for 4wd hi or 4wd low the transmission responds by limiting the shifting but I don't get that wheel chatter when turning a tight radius. I don't know if the front driveshaft is engaging or the front diff isn't engaging. The light blinks on whichever 4wd I put it in. When I put it back to 2wd the light blinks for a few seconds then stays on. Any help is appreciated.

[ccc]

Okay, can anyone direct me to a 4wd forum that might be of some help with this? Any help is appreciated.

[trbankii]

First step would be to narrow things down. Check to make sure that the driveshaft is engaging and go from there.

[More Power]

Expanding on what trbankii suggested, I'd put the vehicle on a lift. Have someone sit in the driver's seat with the ignition key in the ON position and transmission in neutral. Have someone listen for the front axle acutator and have someone listen at the transfer case while the driver selects 4HI - wait for 30 seconds, then 2HI. Slowly rotating the rear tire/wheels by hand may help you determine whether the txfer case is shifting and whether the front axle acutator is actuating... Beyond that, it will take some circuit tracing to verify whether power is making its way to the servo actuator on the tsfer case and axle... before buying parts.

Jim

[ccc]

Thanks for the suggestions, I did try pushing the 4wd button with the key on and the truck in neutral. I got under the truck and the transfer case motor is shifting but nothing is happening with the diff acturator. It is a five pin connector (but there are only three wires, black - brown and green) I took the connector loose where it connects to the harness. There are two wires, brown and green. I tested them for current accross the poles and to a ground with both a test light and a voltmeter. It doesn't appear there is any current to it at all. The harness goes up by the firwall but I haven't found where it surfaces on the top side. I then checked the fuse box inside the cab. #24 fuse is marked 4wd. the top side is hot when the key is on and the fuse is good. I then took the dash off to check the switch. I didn't find anything loose and since the transfer case is getting signal from the switch I assume it is good. Any suggestions? Can I wire a switch directly to the actuator? If so, is one of the wires hot and the other ground? It appears there is a second sensor on the diff that I would guess is the sensor that tells the system the front diff is locked and would stop the light in the switch from blinking (it only blinks in 4wd high and low)

[ccc]

Update: when I push the 4wd button with the key on (motor off) the transfer case engages and I can't rotate the front drive axle. The front diff does not lock in though so I tested the harness for voltage at the actuator and I don't have any. I then tested the harness at the diff sensor on top of the diff, the transfer case sensor on the dirvers side of the diff and I don't have any voltage there either. I traced the harness up the side of the firewall, over the bell housing and into the large harness about where the glow plug relay is. It doesn't appear to be a wire issue or connection. The fuse (24) is good. any ideas?

[crashz]

I haven't had a lot of experience with these actuators, however it seems like the switch would trigger a relay for the front axle actuator. Is there a relay for it underhood?

[ccc]

Thanks Crashz, it sure acts like a relay but I can't find one. Logiclly, it's the switch but it just doesn't make sense that part of the switch would work. The transfer case is getting signal from the switch, so one side of the transfer case sensor should energize when that happens - but it doesn't.