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all wheel drive

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 88bblazen, Dec 14, 2005.

  1. 88bblazen

    88bblazen Registered Member

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    My buddy has a 74' Blazer he says it has all wheel drive. What are the pros and cons of this setup and the dos and donts if there are any. Thanx again to all.
     
  2. BlazerFarm

    BlazerFarm Texagonian Premium Member

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    Well, it's not called "all wheel drive" (I think of Subarus when I hear that) but I think what he's referring to is "full-time 4 wheel drive". That used the NP203 chain drive transfer case and there were no lockout hubs on the front axle. It's pretty hard to find stock setups like this anymore since most people converted them to part-time 4WD with a kit like Milemarker's and some Warn locking hubs. I converted two different trucks back in the early 80s. GM abandoned Full-Time 4WD on their light trucks in (I think) 1979 or 1980.

    I guess the pros are that you have 4WD all the time and don't have to get out and lock hubs.

    The cons are a few. There is a perceived loss of gas mileage since you are turning your front driveshaft and axles all the time. Your turning is affected some since you are always in 4WD, you might feel some wheel hop in full lock turns. The biggest con I can think of is if you break your front driveshaft the transfer case sends all power to the least resistance path like an open differential due to the planetary gear driven case. You aren't going anywhere (someone correct me if I'm wrong). The NP203 is also heavy and it's common to stretch the chains. I stretched one in my '76.

    All that being said I wouldn't mind having another NP203 driven Full-Time 4WD Blazer again. I kind of miss it.
     
  3. mechted

    mechted 1 ton status Premium Member

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    IIRC, its also harder on front tires with full tume 4wd than part time

    essentially, it a similar system to a Subaru (i think) basically 3 differentials, front, center, rear Center (back of t-case) sents power either front or rear when in "high" or "low" and it locks for both front and rear when in "high-lock" and "low-lock"
    DO NOT use "-lock" mode on the street!
     
  4. SUPER'BURB

    SUPER'BURB 1/2 ton status

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    I think you are wrong:D (but it could be me again).

    My dad has a '76 full time 3/4 ton with no front drive shaft (that would be my fault and I still need to put the new one in:o ) and it continues to send power to the rear tires just fine. When it broke I was 200 miles from home, I just took it out and drove home. The front output makes a "CLANK" putting it in gear now but besides that it drives well enough.
     
  5. BlazerFarm

    BlazerFarm Texagonian Premium Member

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    I know it will still work without the front driveshaft if the tcase (NP203) has been converted to part time. Could that 3/4 ton have a NP205 instead? I'm pretty sure that those didn't suffer from that problem.
     
  6. SUPER'BURB

    SUPER'BURB 1/2 ton status

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    Only if the fulltime 4x4 came from the factory with a NP205 (I thought it was NP203 option only). If it was an option I will need to crawl under that thing and go back to retract my statments:doah:maybe.
     
  7. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    All "full time" are 203, end of story. If it has front lock out hubs, it is 205 or converted 203.

    A 203 will pull with no front drive shaft if you have it in one of the "lock" positions. "High Lock" would work much the same as "High" (and exactly the same as a 205 in 2WD) if there is no front shaft.

    Bottom line is that it's a a good strong setup and an early attempt at what is now called "all wheel drive". There is the added wear and marginally lower fuel mileage, but those are generally not as bad as people make them out to be. And you really can't run locking diffs at all without a part time kit. If you try, it will ruin the road manners and wear out (or break) everything at warp speed.

    I had a 76(?) Scottsdale SWB as one of my very first 4WDs and it was a fine vehicle. The "full time" worked great on dirt roads, "hunting trails", power lines, gravel roads, light snow and ice, and so on. But if it ever got too slick (like really, REALLY slick), you would wind up with 1 tire spinning just like a one legger. Just slip it into Hi/Lo Lock and roll on...
     
  8. SUPER'BURB

    SUPER'BURB 1/2 ton status

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    Thanks you just saved me crawling under a truck in the mud. It is in H-Lock.
     
  9. Desert Yeti

    Desert Yeti 1/2 ton status

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    This has all been covered pretty much already, but I'll restate that in LOCKED mode (hi or lo) the 203 sends power front and rear regardless of shafts, just like any other traditional t-case. In unlocked mode, the case acts as a center diff, allowing for good street manners. It is indeed a somewhat primitive version of what they're now calling "all wheel drive", the difference being that you could actually lock it up for real when you wanted/needed to...which sometimes isn't true of the newer cute-utes with "all wheel drive".

    Interesting side note on the 203 converted to part time... I don't know that I'll ever have a lot of use for it (maybe trying to make a tight turn on the rocks with a locked front axle) but a converted 203 gains what amounts to a 2-LO setting that could even be run on the street. :)
     
  10. Thunder

    Thunder 3/4 ton status

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    Hmmm....... I thought "All Wheel Drive" ment you have a locker in the back and one in the front=power going to all four wheels. The only American vehicles that had had "All wheel drive" were IH Harvesters. You could get them with a detroit locker in the back and a true trac in the front.
    Blazer never came with "All Wheel Drive"
    I think you guys are talking about "Full Time" 4x4.
     
  11. BadDog

    BadDog SOL Staff Member Super Moderator Author

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    Yeah, we are technically talking about what GM called "full time 4wd". But it's just a name, and you really can't start splitting hairs over the names. "All wheel drive" by no means indicates all "4 get equal torque" any more than "4 wheel drive" does. Do you really think Subaru, Porsche, and others have front and rear lockers? Most anything ever called "full time", "4 wheel drive", "all wheel drive" or dozens of other monikers will be SOL if you get one or two tires off the ground. And with a LS in the front, by your standard, even the IH is not "all wheel drive" since the front LS will "slip" at some point and provide what is effectively 3 wheel drive, even when the tcase is in 4WD. Where do you draw the line? And "all wheel drive" by your definition would not even be remotely streetable. The "full time 4 wheel drive" systems of the 70s are much closer to the modern "all wheel drive" than an IH with a part-time case (NP200s weren't they?) with LS and Locker…
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    I can't believe a 203 is anything other than "all wheel drive". During normal operation the capability is there to put power to ANY wheel that is touching the ground, and there are three differentials in the system.

    I don't see that being any different than other AWD systems, although I know some use a viscous coupling.

    Notice that Subaru USED to call their vehicle 4wd when in fact there was no way to "lock" the center differential, now they call it AWD.
     

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