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1988 dodge w150 318 4wd doesn't work but T case is engaging

Discussion in 'Pre-1994 trucks, commercial vehicles' started by upser145, Dec 10, 2017.

  1. upser145

    upser145 Member

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    my 1988 w150 that I haven't had for long i recently found out the 4wd isn't working it has manual locking hubs and i made sure to lock them and i can put the tcase in 4wd and get under the truck and can no longer turn the front driveshaft by hand but the front tires won't pull so it seems the tcase is engaging. I've heard some people say to lock my CAD and it could fix it but being that I have little experience with a 4wd front end I'm not sure if locking it would be good or possibly a bad idea or what exactly it does any help would be greatly appreciated. also noted the first time i ecer put it in 4wd it felt almost as if it was popping in and out of 4wd and kinda hopped when i hit a dry patch of road like it would if it was in 4wd but I've never been able to get the fronts to spin
     
  2. Devildodge

    Devildodge Active Member

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    Do you know if the manual hubs where added by someone. If you have C.A.D. then someone did. The C.A.D. Did away with the manual hubs.

    If you do still have C.A.D. you can lock it yourself, or buy a kit.

    V10 RAM getting some due rest and rectification of Pennsylvania abuse. (at https://www.allpar.com/forums/threads/v10-ram-getting-some-due-rest-and-rectification-of-pennsylvania-abuse.164786/ )

    You can check out this link, it is my challenge with C.A.D.

    If your truck came with manual hubs it wouldn't have C.A.D., so if it does I am not real sure why someone would do that modification.

    Let us know some more info and we will be glad to help.
     
  3. Devildodge

    Devildodge Active Member

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    The C.A.D. is on the long axle tube under the truck. Held on by 4 bolts and would have a vacuum bulb and a switch.

    Does your 4wd light come on?

    If you do have C.A.D. then you may have a broken fork.
     
  4. upser145

    upser145 Member

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    I am not sure if they were added or not. as soon as i can find the cad and figure some more info out i will update thanks for your time guys!
     
    Devildodge likes this.
  5. pt006

    pt006 Active Member

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    The axle disconnect system is a 2 piece axle connected by a sliding spline. When the spline is disengaged, the inner axle spins, but not the outer axle. When the spline is engaged, the inner axle turns the outer axle and now you have 4WD. The spline is slid back and forth by a fork which is driven by a vacuum piston/diaphragm. When vacuum is applied to either of the 2 vacuum ports, the piston/diaph. will move one way or the other [engaged or disengaged]. When the spline is fully engaged it hits a switch and an electrical signal is sent to the dash to light up the dash screen. Says 4WD ENGAGED [I think].

    Be aware that the sliding spline will not disengage if there is tension on the axle. Rolling back and forth will help.
    Also, the sliding spline will not engage if the splines of one axle do not line up with the splines of the other axle. Rolling back and forth will help. It important that the dash light works. This verifies that the splines are fully engaged. NEVER operate in 4WD unless the dash light is on, because if the spline is only partially engaged then serious damage can be done to the sliding spline or the axle spline.

    The truck must be running to produce vacuum. Check hoses for leaks. ----- good luck-----
     
    NYBo likes this.

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