Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Transfer Case (np208) nasty noise, problems is there a chain?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by MudNurI, Jun 10, 2002.

  1. MudNurI

    MudNurI 1/2 ton status

    Joined:
    Jul 15, 2001
    Posts:
    2,113
    Likes Received:
    0
    Location:
    VT
    John took Mudnuri to work today, his first time actually driving it, more than around the block, and was very worried about the noise I posted about earlier that sounds like a Jake Brake. His commute is on I-91, posted speed of 65, he thinks he was doing about 65-70 as he was with traffic, speedo was at 75-80... anyway.

    The noise comes when you are going a steady speed, as in, not accelerating or decellerating, just cruisin, when you let off its REALLY loud.....he said that maybe there is a chain inside the transfer case that's shot? Someone that is a transfer case guru- please give me some input. It's not the U-Joints, those were just replaced when we went back to 1/2 ton Axles..everything is tight under there, etc.. Transfercase Guru I await your reply!

    John has this fear that its going to lock up and I'm going to end up rolling over and over,,,,1 of his brother's work truck just blew it's transmission, at 45 mph, and it locked the rear tires,,luckily it's not lifted like me, but for some reason John is freaking and says- no more taking the truck, till we get this figured out.

    thanks!
    Brandy /forums/images/icons/crazy.gif
     
  2. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

    Joined:
    Jun 16, 2000
    Posts:
    1,932
    Likes Received:
    0
    Location:
    Sims, NC
    Your 208 definitely has a chain, but it would have to have an incredible amount of slack to make the noise you are describing. Check the slack by jacking your truck up, putting it in 4 high and trying to rotate the front and rear drive shafts "against" one another. You should be able to tell how much slack you have. More than a little is too much. Hope this helps.

    Mike
     
  3. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    Not sure (as I have no little experience with the 208), but if it is the same as a part-time converted 203, the chain only turns in 4Hi and 4Lo, during 2WD operation the chain does not rotate in the 203, but not sure if the same can be said for the 208. Anyone confirm/deny this? If that is the case and he is in 2WD is may be a bearing. What are you running for a tranny (sorry can't get into your profile while writing this). Could be a syncro/bearing whine/hum if it is a manual (under tension either accelerating or decelerating).
     
  4. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Yep, the chain in a 208 just drives the front output shaft. So unless the t-case is in 4WD (or the front hubs are locked), then it should be moving. /forums/images/icons/cool.gif
     
  5. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    </font><blockquote><font class="small">In reply to:</font><hr />
    So unless the t-case is in 4WD (or the front hubs are locked), then it should be moving.

    [/ QUOTE ]

    You meant shouldn't....right? Just checking to remove any confusion.
     
  6. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Yep! That's what happens when you're trying to type while the kids are screaming and the wife is trying to tell ya something all at the same time. /forums/images/icons/blush.gif The chain should NOT be moving in 2WD. /forums/images/icons/cool.gif
     
  7. MudNurI

    MudNurI 1/2 ton status

    Joined:
    Jul 15, 2001
    Posts:
    2,113
    Likes Received:
    0
    Location:
    VT
    so if the case is the chain is not moving, since I'm in 2wd, and my hubs are out,,,,it has to be in the transmission. Which is what I thought first, but John said no...I'm thinking- and I may be totally off base, but that 4th gear is shot...since it only makes the noise in 4th gear, etc... is it possible to replace 1 gear, or am I outta luck and need to start searching for a replacement transmission?

    Thanks Guys! /forums/images/icons/grin.gif
     
  8. SAVAGE1

    SAVAGE1 1/2 ton status

    Joined:
    May 22, 2000
    Posts:
    1,104
    Likes Received:
    0
    Location:
    BAY AREA, CA
    I get the same exact noise out of my 208. I have a new engine, tranny and rear driveshaft, the 208 is the only thing I didn't replace. From reading previous posts on this same subject, most people concluded that it was the cause of a bad driveshaft angle at the slip yoke.

    When did you notice the noise? Has it gotten worse? My noise started when I put in my new driveshaft and changed my rear pinion after my 3/4 ton swap. I get it as speeds over 45 when I let off the gas.
     
  9. MudNurI

    MudNurI 1/2 ton status

    Joined:
    Jul 15, 2001
    Posts:
    2,113
    Likes Received:
    0
    Location:
    VT
    I'm going to try to remember being as I haven't had her on the road for long. If I remember correctly, back when he (previous owner) put the 3/4 ton axles on it started, (his girlfriend and I are friends, so I have riden in the truck numerous times)..however I am back at the axles that came from The General himself...only difference is the gears,,along with the lift.

    if this is what it is- how do I fix it? check the angle of the drive shaft? What's an acceptable angle? sorry to sound so stupid, but John REALLY is nervous about this noise, and I wanna drive my truck LOL...if its the driveline being at a bad angle, what's my worse case senario if I continue to drive it, like this weekend, without getting it fixed? Is something going to give, break, freeze, cause me to roll ??

    thanks guys!
    Brandy /forums/images/icons/grin.gif
     
  10. trailblazer87

    trailblazer87 1/2 ton status

    Joined:
    Jun 11, 2002
    Posts:
    707
    Likes Received:
    0
    Location:
    Madera, CA
    I had the same problem until I lowered my T-case. What had happened was the lift blocks rotated my rear axle pinion side upward to remove some of the driveline angle, the problem is when both sides of the driveline are at different angles it vibrates. When you are on the throttle there is enough pressure to keep it from vibrating, when you are cruising there is just a slight amount of pressure on the U-joints and they vibrate. My T-case is a 208and has its own problems, but that was one of them. If you went to the smaller axles it just made your driveline have to reach that much lower, and now the vibration. If you don't get this fixed soon you will start blowing U-joints every couple of weeks. I got pretty good at changing them on the side of the freeway, trail, mud hole, dunes, and once in the snow. The only problem with a Blazer is the real short driveline, otherwise there is no drawback.
    Hope this helps.
     
  11. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    Could be lots of things or even combinations of things. Only doing it in one gear makes me think it might be a transmission problem but it may be just accentuated by one of the gears (4th in your case). Driveshaft angles (especially with slip yoke), worn bearings, and maybe even a bad u-joint can cause problems. Unfortuneately the driveshaft can be a good transmitter of clunks and bangs and can make a rearend problem sound like it's coming from the t-case and vice versa. Is it this weekend you said you were going to head South? I am not available Saturday afternoon (girlfriend's brother is getting married) and Sunday afternoon (first truck pull of the year), but Friday afternoon/night, saturday morning, and sunday morning/night I will be around if you wanted to swing it by and I could take a look and see if I can diagnose it (I'm 2 minutes off of I91 in Hatfield just North of Northampton and 20 mins North of Springfield). PM me if interested, always glad to help out, as others have helped me.
     
  12. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    Just came across this in another post and thought it might be relevant:

    1st post by twenty below0: <font color="blue"> OK, I was driving down road today and romped it! Just as it shifts from 1st to 2nd there's this HARD BANG.....then nothin....like it's in nuetral, but with a whine now when you rev it.Checked the flexplate and it's cracked but has been for about 3 weeks, still starts fine but put it in gear and nothin but a whine, that get's a little louder the higher the rpm's are, no movement in the drive shaft at all.

    So please tell me it's the torque converter and not the tranny, ..again the flexplate is fine and bolted up to the motor and plate..... this is my daily driver right now so the quicker the better. THX .</font color>


    reply by MR.Chevy4x4: <font color="red"> What transfer case are you running? I have had the very same thing happen to me before and it was a broken chain in my 208 transfer case. Contrary to popular belief, a truck running a 208 case with a broken chain will NOT drive in 2 wheel high. Try putting the truck in 4-low and see if it will drive. This is how they loaded mine on the wrecker back in '87(it was still under warranty). Just a thought! </font color>


    So maybe the chain does do something in 2Hi (if he has his facts straight), or turns somewhat due to parasitic drag (much the same as the front d-shaft on a 205 will rotate when in 2Hi). Anybody who knows the inner working of the 208 confirm this (the 208 is not a case I am too familiar with).
     
  13. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Here's the description of operation for an NP 208 from a GM service manual:

    "In 2H range, torque flows from the input gear to the planetary assembly and annulus gear which rotates as a unit. Torque is transferred to the mainshaft through the planetary carrier which is splined to the mainshaft. Torque flow continues through the mainshaft and rear yoke which is splined to the mainshaft, and finally to the rear properllor shaft and axle. In 2H range, the sliding clutch remains in a neutral position and does not lock the drive sprocket to the mainshaft. As a result, torque is not transferred to the driven sprocket.

    In 4H range, input torque from the input gear is transmitted through the planetary assembly and annulus gear and through the mainshaft in exactly the same fashion as in 2H range. However, in 4H postion, the sliding clutch is shifted forward and into engagement with the mainshaft clutch gear. This locks the drive sprocket to the mainshaft through the sliding clutch. Torque is now transmitted through the drive sprocket to the driven sprocket by the connecting drive chain. Since the front output shaft is splined to the driven sprocket, torque now flows through the front output shaft to the front propellor shaft and axle resulting in high range four-wheel drive.

    In 4L range, the path of torque through the transfer case is exactly the same as in 4H range but with one major difference. In 4L range, the annulus gear is shifted forward and into engagement with the lock plate. Since the lock plate is fixed in the case, the annulus gear is hel staionary and down not rotate. This cause the planetary pinions to rotate about the annulus gear internal teeth producing a gear reduction ratio of 2.6:1."

    Sounds like the transfer case described in that other post had a problem other than a broken chain. /forums/images/icons/shocked.gif
     
  14. MudNurI

    MudNurI 1/2 ton status

    Joined:
    Jul 15, 2001
    Posts:
    2,113
    Likes Received:
    0
    Location:
    VT
    wow now that was some mumbo jumbo technical talk if I ever do say!

    I'm concerned now, either it does or it doesn't (the chain move that is)...I doubt very likely that my chain is broken, my concern is that my chain could be stretched out... that along with the angle of my driveshaft, could be causing this probem.

    Leadfoot- I need to talk to John about this weekend, fathers day and all- but I'll know by tonight.thanks! /forums/images/icons/laugh.gif

    Brandy
     
  15. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Brandy, this is the important part of the "mumbo jumbo": /forums/images/icons/wink.gif

    "In 2H range, the sliding clutch remains in a neutral position and does not lock the drive sprocket to the mainshaft. As a result, torque is not transferred to the driven sprocket. "

    The 2 sprockets (gears) that they're talking about are the one that drive the chain and the one that is driven by the chain. They aren't doing anything because the drive sprocket isn't engaged. /forums/images/icons/cool.gif
     
  16. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    That's what I thought too (see earlier posts), but what MR.Chevy4x4 said had me wondering. So I guess it's not the chain.
     
  17. MudNurI

    MudNurI 1/2 ton status

    Joined:
    Jul 15, 2001
    Posts:
    2,113
    Likes Received:
    0
    Location:
    VT
    ahh ha.. so that leads me to believe further that it's not a transfer case problem. I am now narrowed down to either 4th gear is shot, or its a driveshaft angle issue. Keep the idea's coming guys....I just wanna drive it..if I can come up with something to tell John...ie...the worst thing that can happen is I break a U-Joint etc... than MAYBE he'll let me drive it..but if he thinks for a minute that I may end up with it on it's roof well, than I'm outta luck!

    Brandy /forums/images/icons/shocked.gif
     
  18. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

    Joined:
    Jun 16, 2000
    Posts:
    1,932
    Likes Received:
    0
    Location:
    Sims, NC
    I said what I said based on my experience. The only transfer case I have ever torn apart is a 205. I bought a new K5 in '85 and the incident happened in '87. I was driving down the road and BANG! No more power to the rear wheels. I called the dealership and they came and picked it up. The roll-back truck driver put it in 4 low and pulled it up on the truck. I am pretty sure I still have the service bill that says they replaced a broken chain in the transfer case. That was the story I was given buy the service department manager when I went to pick it up. If what I said doesn't hold water, then it wouldn't be the first time I was wrong, or to be politically correct "misinformed"! /forums/images/icons/grin.gif

    Mike
     
  19. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Joined:
    Nov 28, 2000
    Posts:
    3,112
    Likes Received:
    1
    Location:
    Western Massachusetts
    That's not your fault but the fault of the Service manager and/or mechanic. Sometimes they simplify the work done so that the "layman" can have some sort of explanation they can understand. The chain probably was worn and needed replacement so instead of saying it was "stretched" they said it was "broken". End result is that it was replaced along with probably the part(s) that actually broke. They do this (my friends work at different auto dealerships and tell me these things) because if they said the chain was stretched, SOME customers would say things like "couldn't you unstretch it?", "isn't there and adjustment on that?", "I want to see just how stretched it was", etc. etc.

    Some dealerships/auto repair places do this to minimize confusion but there are some that do this to be dishonest and hide the fact they are taking you for a ride (you have to be informed and beware). In my experiences most are very honest but the few who are dishonest give everyone a bad name.

    My bet is you blew the rear output (hense no 2wd/rwd, so putting it in 4hi/lo allowed it to move under the power of the front axle). When they pulled it apart they saw the chain stretched so they replaced it, and instead of causing any confusion, just told you the chain was broke (or it broke during disassembly).

    It's not your fault, just what they told you. You were just trying to help out so that is cool (and what this site is all about). I/we just wanted to make sure the facts about the case and chain drive are/were correct. I too have little experience with this case but have been dealing with them more and more so I wanted to get my facts straight as well. Anyways thanks for the input /forums/images/icons/cool.gif /forums/images/icons/smile.gif
     
  20. 85chevy4x4

    85chevy4x4 Registered Member

    Joined:
    Apr 26, 2002
    Posts:
    63
    Likes Received:
    0
    Location:
    kansas city, kansas
    I am also having problems with my 208 transfer case on my 85 chevy 3/4 4x4. When I go to stop I have to keep one foot on the gas and one on the brake otherwise it makes this clattering noise and seems like it's in neutral. It seems to be getting worse lately. I have to shift into neutral then shift into 4hi or 4 low and it grinds then shifts in then back out to 2hi, then throw it back in drive until it acts like it's normal again. Could this be a worn chain? It only does it like if I'm going down the road above 50 then go to stop at a stoplight. If I'm just doing 30mph or under and slow down it doesn't do it. The tranny doesn't slip and shifts fine. /forums/images/icons/confused.gif
     

Share This Page