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NP205 pops out of low

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mountainexplorer, Apr 23, 2002.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    I have a '78 3/4 ton 4x4 with an SM465 and NP205. The Transfer case pops out of low range, especially when turning while locked in 4wd. What would be the cause?

    Also, I have an '80 that has a 205 with the slip yoke. Would it be easier to convert it to a fixed yoke or easier to just use another T-case that already has a fixed yoke?
     
  2. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    I had a problem with flex and the tranny hump would hit the shifter when in 4Lo and cause it to come out. If the clutch teeth or gear teeth are worn it can also cause it to slip out under stress, but I would check for floor clearance first (also it was hard to tell on a level surface that there was interference, I had to manually flex it with a fork lift to figure out what was happening). As far as swapping a complete case or just the fixed yoke tailshaft. You can swap in a fixed yoke tailshaft while the case is still in the vehicle so swapping in a fixed yoke tailshaft is easier. It is harder to find just a rear output but can be done (as I've done it) as opposed to a whole case.
    Considering yours is slipping out of gear it may not be a bad idea to find a complete spare and swap it in. Hope this helps.
     
  3. mountainexplorer

    mountainexplorer 1/2 ton status

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    Theres plenty of clearance as far as the shifter goes. My '78 is completely stock (that is no lift, and little 31" tires). It sounds like something internal. When it pops out, it makes a loud clunk, not as if it were to just slip out. I do know that the clutch in it is pretty worn and bad. Plus now, the tranny jammed in low gear and the shifter is stuck in the position of 3rd. Its always one problem after another.
     
  4. m j

    m j 1/2 ton status

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    linkage worn not allowing full engagement
     
  5. MudbogAD

    MudbogAD 1/2 ton status

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    Mine would slip from 4lo to 2lo all the time until I found out that it wasn't fully engaging into 4lo. It was hitting the floor and not fully engaging. I just adjusted the cover forward about 1/2 of an inch.
     
  6. HarryH3

    HarryH3 1 ton status Author

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    Pull up the shifter boot and see how close the shifter really is to the edge of the floor when it's in 4Lo. I had a brand new '79 F-150 that would kick out of 4Lo every time I started up a hill. 2 minutes with the tin snip and it never happened again. /forums/images/icons/cool.gif
     
  7. mountainexplorer

    mountainexplorer 1/2 ton status

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    I'll double check the shifter clearance again. Although I'm pretty sure it wasnt hitting or rubbing, at least it wasnt when we put the body on the frame. My '78 used to be a 2wd. When we put it's body on a '79 4wd frame, we cut out the floor and used the '79 cab center-hump. That was a year and a half ago since I looked under the boot.
     
  8. HarryH3

    HarryH3 1 ton status Author

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    You want to have someone watch it while you drive. A sagging body bushing and/or tired engine/tranny mounts can let the body meet the shifter as torque moves things around.
     
  9. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    my buddies did that to but out of high. had a bad thrust washer in it somewhere. he had it rebuild... not a cheap fix.
    600 bones later
    grant
     
  10. mountainexplorer

    mountainexplorer 1/2 ton status

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    Yikes, I'm hoping it wont need a rebuild. I paid $600 for the whole running truck, then just put my '78 body on it. It only does it in low. 4-high works fine, no noises or anything. My cab/body mounts are all good, since I made sure I used good ones (I was too cheap to buy new) when I swapped bodies. I'll know for sure or not if it's the floor/shifter clearance in the next few days (the truck is 85 miles away from me right now). I gotta pull the floor pan out anyway to get the tranny shifter un-jammed.

    The same weekend my 4spd jammed in low, I also discovered my oil in my '75 Blazer was a sparkling metallic grey color. and I still havent discovered the cause of the mysterious T-case seal leak in my Suburban. I filled it to the full point a month ago. Since then Ive leaked out a good 2 quarts in various places Ive parked. Every time I check it now, it's overfull; but it still leaks everywhere and now clunks like the tranny to T-case sleeve is about ready to sheer off it's splines. My vehicles like to do this to me all at once. 10 trucks and I'm down to one I can drive.
     
  11. reedmit

    reedmit 1/2 ton status

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    I have had my truck for many years now and for the first time ever it did this the other day. I dont have any fancy twin stick or anything but I was in 4low and it poped out into 2low. I dont have 2low in my 205. I pushed it forward felt in go in and got it under pressure and it did it again. Now my linkage is rattling pretty good when I go down the freeway. Do you think it is just something with the linkage? Can I set it up to have 2low without doing any grinding? Or is my t-case screwed?
     
  12. m j

    m j 1/2 ton status

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    mine used to do that but it would hop into front lo.
    it is just the linkage is a bit worn.
    if yours is going 2lo with rear engaged you can give the lower shift rail a smack to drive the shift fork for the front lo engagement, it only has to hang a bit and the worn linkage wont let it grab fully.
    if yours is like mine was then it is the upper rail to get rear drive to engage.
    not catastrophic but the possibility of making a wear pattern that the shift clutch wont want to slide past easily even once the linkage wear is fixed does exist.
    I would look at the pivot that the stick rides on as one place for wear, and the bushings or lack there-of on the bent link bar from the stick to the (hmmm whadaya call that plate in between the shift rails?)
    a rebuild kit for the 205 is about $170 from National drivetrain
     
  13. johnnyK5

    johnnyK5 Registered Member

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    It sounds to me like you need to lube up the linkage INSIDE your transfer case SHIFTER BOX- (Not the transfer case). I had the same problem with mine. I removed the floor panel around the shifter so I could get to it easy.
     
  14. mountainexplorer

    mountainexplorer 1/2 ton status

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    Well, I pulled the floormat out and checked, and the shifter all the way foreward still has plenty of clearance from the floor board. The shifter all seems to be in place and in proper working order. Actually, it doesnt pop all the way out of low, it just clunks really hard when turning, as if something was binding up and popping. Didn't figure that out yet, but at least I got the tranny to shift now.
     

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