Ive got a stock 04 lb7 crew cab 2500hd. It has a manual 4x4 shift lever on the floor. I know its not the acuator on the front diff, I know its not the switch mounted on top of the transfer case, I know its not a fuse. Just wondering if anyone knows of a commeon problem that mite be the cause.

is it giving a Range Shift Inhibited message on your DIC? is the lever just not throwing in or is the 4x4 light just not coming on?

Does it switch ranges? Have you checked for pump rub? I have seen a few of these cases, that had pump rub, and was not caught quick enough and had this problem. They would make range changes, but not mode changes.

No evidence of pump rub. There are no leaks or stains anywhere. It does go into low gear or granny gear. Front diff does not lock into 4wd and light doesnt come on. Truck has 83,000 miles. I was thinking of removing the t-case switch and manualy activating it to see what happens.

i dont understand.....it does go into 4Low but you're saying the front diff doesn't lock? how can you tell? our front diffs are not locking unless you put an aftermarket locker in..they are open diffs.
on edit: there also is no "actuator" on the front diff unless you installed an aftermarket locker....the only actuator is on the t-case and it is a self-sealed unit ....600 bucks to replace...try putting dielectric grease in the NSBU harness connections, it worked for me

the trucks DO have an actuator on the front diff. mine has a floor shift lever also . if you turn the key on dont start it and shift it into 4x4 you should hear the little motor (will sound like zzzzzttt)shift in the switch on top of the transfer is the light switch to tell you 4x4. I havent had one of these transfers appart but if I remember right the lever is spring loadded INSIDE the transfer

i dont understand.....it does go into 4Low but you're saying the front diff doesn't lock? how can you tell? our front diffs are not locking unless you put an aftermarket locker in..they are open diffs.
on edit: there also is no "actuator" on the front diff unless you installed an aftermarket locker....the only actuator is on the t-case and it is a self-sealed unit ....600 bucks to replace...try putting dielectric grease in the NSBU harness connections, it worked for me
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My truck definetly has a acuator on front diif, and who said anything about a locker type diff???

the trucks DO have an actuator on the front diff. mine has a floor shift lever also . if you turn the key on dont start it and shift it into 4x4 you should hear the little motor (will sound like zzzzzttt)shift in the switch on top of the transfer is the light switch to tell you 4x4. I havent had one of these transfers appart but if I remember right the lever is spring loadded INSIDE the transfer
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I dont get the zzzzzzz noise. I am pretty sure I have an electrical problem. The fuse is good. A repair shop replaced the actuator, replaced the switch on top of transfer case, and I checked all fuses. Still no zzzzz from acuator. Possible ground problem. The shop gave me my money back also, just for the record.

it may be a brain box for the 4x4 mabe check the voltage on the wires to the actuator you may have to have a buddy help. shift the levor in and out with a volt ohm gauge hooked to it . is your truck lifted ?? I have seen a lifted truck pull the shaft out of the housing that has the actuator in it . if this happend it dropped a washer into the shift assembly that keeps the axle from going in all the way

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My truck definitely has a actuator on front diff, and who said anything about a locker type diff???

you said that it would not lock...our front diffs never really "lock" without an aftermarket unit. the actuator that sticks out the pass. side of the front diff is this:

Actuator . 26060073 . $156.17

and if I am not mistaken, this is the "acuator" you are talking about on the Tcase....i have one that i ordered cuz i thought that was my problem and it wasn't, I just put di-electric grease in all connections and everything was good to go. but if you need this I have one...I would ship it to you for $650.

263 . . . . 34 - Actuator . 88962312 . $718.94