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what's best trans/xfer case for a 75?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 75K5, Dec 7, 2001.

  1. 75K5

    75K5 1/2 ton status

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    what\'s best trans/xfer case for a 75?

    I am building more of a hot rod blazer than an off road one. I want to retain 4wd, but I want to maximize handling and ride quality. I am not planning a lift kit or mud tires, but I do have a TPI, 383 kit, and possibly a whipple charger in the near future :)

    Anyone have suggestions for the best transmission and transfer case? I am not farmiliar with the chevy world yet, but I'd like to find an electronic-automatic that will fit.

    Can anyone tell me if I would have to switch to IFS to use the transfer cases that switch from 2wd to 4wd with the electronic actuator and push button??? Has anyone switched to IFS on a 73-91 K5?

    lastly, are there any IRS configurations available for this platform?
     
  2. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    LOOK OUT! The IFS rants are gonna fly!

    There are tons of options but the number one piece of advice is stay away from that mickey mouse chicken $hit IFS garbage. Go crawl under a newer GM truck and have a look around at it. Its alot more complex and not as strong, all for a little better ride.

    If the sky is the limit here then I'd dump the 203 T-Case. It aint a bad case but the 205 is gear driven and has a 2wd position. The 208/241 T-Case aren't quite as strong but have a lower low range, (208=2.61 241=2.71 205=1.96). These cases are plentiful and cheap. The 208/241 are also lighter and a lot easier to put in.

    As for tranmissions, the TH350 is good all around slush box. The TH400 tougher and if you want to go over kill, get that. The 700R4 isn't as bad as people say, if you get the right one that is. Try to get one from 1987 on up or so (they did some upgrades to make it better). The 700R4 is no where near as tough as the TH400, but it has lower gears and overdrive, I like this tranny.

    Dont wanna have anything to break....TH400 and NP205.

    Want better mileage, eaiser to install T-Case, and cheaper, go TH700R4 and the NP208 or 241.

    The TH350 and NP203 you have now are good too.
     
  3. 75K5

    75K5 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    so If I get a 205 can I avoid dealing with locking hubs, or do I still have to tinker with the hubs when changing from 2WD to 4WD?

    Is the 700R4 what they use in the new trucks? Overdrive is a MUST, and I was hoping there would be a computer controlled automatic available.

    If IFS isn't that much better, I won't bother with it. I really wish there was a coil spring setup available instead of the leaf springs, but I'll just have to live with it.
     
  4. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Re: what\'s best trans/xfer case for a 75?

    The 203 t-cases are the ones where you will need to address to the locking hubs.

    If overdrive is a MUST, get the 4L80E tranny. Its the overdrive-version of the 400 tranny.


    I'm not picking my nose...I'm just pointing at my brain!! [​IMG]

    <a target="_blank" href=http://coloradok5.com/gallery/thatK30guy>The K30 Collection</a>
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: what\'s best trans/xfer case for a 75?

    <blockquote><font class="small">In reply to:</font><hr>

    I want to retain 4wd, but I want to maximize handling and ride quality. I am not planning a lift kit or mud tires

    <hr></blockquote>
    Not the way I'd build a K5...[​IMG] That being said I'd look for a newer Tahoe or something with a IFS front, a full time and part time case (NVG242 I think..)

    Handling and ride quality can be done but a live axle leaf sprung short tall truck ain't the place to start. You have some major hurdles to clear. Another option is to swap an IFS front end in (I have no idea how hard that would be) and use the AWD T-case and 700R4 from an Astro van. Then lower the truck a little so it's near 2WD height. Add some lo-pro's and some HP and it would be interesting...

    Rene

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  6. HarryH3

    HarryH3 1 ton status Author

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    Re: what\'s best trans/xfer case for a 75?

    Whew! Sounds like you want to spend a LOT of money, turning that K5 into a full size version of the Typhoon. [​IMG] Should be a fun ride, but installing IFS will be a LOT of work to get all of the brackets installed properly so that you can align the front end. You really need to crawl under a late model truck that has IFS and take a close look at what you'll be getting into. There's a lot of stuff going on under there...

    One detail item I can think of is that you'll have to move the oil filter. My IFS S-Jimmy has a remote oil filter because the front driveshaft occupies the space that it would have been in. Our '94 Suburban has an adapter that mounts a small filter sideways, again, to clear the front driveshaft. Since the IFS front ends have the driveshaft on the "wrong" side [​IMG] you'll probably have to do some creative exhaust work as well. Take lots of pictures and keep us updated! Sounds like an interesting project! [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  7. 55Willy

    55Willy 3/4 ton status

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    Re: what\'s best trans/xfer case for a 75?

    Hey a sport truck with some Fill Size attitude. I say go for it, why not? If you really want to keep four wheel drive I would go with the 400 and 205. For an IRS set up you should check out any sport truck magizines and set up for a full size chevy(73 to 91) should bolt in. For doing the IFS I would take some measurements and see if you could just graft the whole other front onto yours.
    You could just find a 89 and up truck that is being parted and get all you need.

    <font color=red>Life is like a mud hole:</font color=red><font color=blue>
    When the S#!T gets deep, you have to keep moving and friends can always pull you out</font color=blue>
    55 Willy's
     
  8. Chris_T

    Chris_T 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    I'd have to agree with everyone saying an NP-205 for strength, of course you get weight with that too, but a whipple charger should keep a smile on your face. Do you want shift on the fly? What do you want to keep 4wd for - off-roading? icy driveways?

    I also like the idea of an AWD street truck, what about something like a J**p Select-trac case with it's own differential? It would allow for 4wd on the street with the center diff unlocked and 4wd off road with it locked. Mash the gas and you have front and rear tires to hook up rather than just the rear. The amount of power you want to put through it might be an issue though.

    I like the OD on my 700R4, but if $$ were no object I'd have a 4L80 in there. Stock IFS will improve the ride and decrease the wheel travel unless you do a whole lot of custom fabrication and build your own control arms etc. If you do decide to go that way maybe take a look at a few mag articles covering off-road racing trucks, you may just get an idea you can incorporate into your truck in one fashion or another.

    What about something in between, say a TTB F**d front end on coils? A lot of tough truck racers like them for the increased handling.

    Okay ... I think I need to go lie down or something, I've just suggested grafting J**p and F**d parts onto a K5. Keep us updated though, sounds like a cool project
     
  9. 75K5

    75K5 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    this is awesome information. I was afraid I was going to take a beating for even suggesting it.

    What I think I am going to do is try to located a late model tahoe that is a rollover. If I can pick one up for less than $2500, I'll take the IFS off of that, and maybe steal some interior parts and other goodies. I haven't even taken a good look at IFS yet, but it it coil or leaf spring?

    I know where I can get a 4L80E for a few hundred bucks. If that is a better choice than the 700R4 that will be the way to go.

    I'll start researching the AWD case in the astros. I hadn't though of that, but for my application AWD would be much better than 4WD. If the astro case can handle the torque, it would be perfect.

    For IRS, I keep looking at the two other cars I have in my driveway, a 94 Thunderbird SC and a 93 Mark VIII. Both have IRS, and I have almost all the extra parts laying around to build another complete IRS. I know that is putting F**D parts in a chevy, but If I could find a way to mount the IRS parts, it would be a cheap fix. Not only that, I could use the Mark VIII air ride shocks and mount a compressor. I wouldn't dare drive a "slammed" truck (I know better), but I could use a Mark VIII computer to have the truck drop 1-2" at 60mph.

    I had looked at typhoons, and almost bought one. But they are a little bit small, and they didn't have the potential that V8's do. Plus my 75 is a full convertable. The torque and HP potential of a whipple charged 383 TPI would be a blast. More importantly, It would be kinda diffrent!!!

    Thanks a ton! I'm headed to the newsstand tomorrow to buy some magazines!

    Brian
     
  10. Triaged

    Triaged 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    I think getting '92- Blazer/Tahoe is a great idea to start swaping in parts but I think with the ammount of things you want to change you would be better off putting your body on a tahoe frame.

    The IFS uses torsion bars for the front as springs.

    Your biggest problem with IRS is going to be finding something that has enough strength to handle the weight of your truck. I don't think any of the ones you mentioned would be any where strong enough. A custom setup would be your best bet.

    The 4l80e is a assome trans...if you can pick one up for few 100 by all means do it! It is electronically controled and will need a controler.

    '71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
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  11. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: what\'s best trans/xfer case for a 75?

    IFS is neither leaf nor coil sprung. Coils would interfere with the cv shafts, so those are out. Leaves simply won't work if you take a good look at it.

    Be prepared to cut your frame in half and weld the newer, IFS part in the front.

    If you want an AWD truck to go fast, I highly suggest the NP 203 case. It's full time 4wd and has a center differential, so it'd be your best bet for a 4wd sport truck.

    Honestly, I wouldn't be at all surprised if, after all this work, you're very disappointed. These trucks are just too fat to fly.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  12. Hossbaby50

    Hossbaby50 3/4 ton status

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    Re: what\'s best trans/xfer case for a 75?

    Isn't the 203 an AWD case. It is in 4 wheel all the time which is what you want. Also it is the only fulltime case that I know of that could handle the power your proposing. Although, I know there are Tahoes and maybe Subs that have AWD. That is more apt to handle your power then an Astro case. My buddy had a Tahoe that was selectable from 2hi, AWD, 4hi, and 4low. It was newer, '99+. I don't know if the frames are the same width as they were back in 75, but you might be able to subframe a Tahoe to get the IFS. Just a thought.

    Also if you can get the 4L80E for cheap then DO it. That is the trans you'll want. It's as strong as a th400, but has OD. The 4L80E is way stronger then a 700R-4. Also make sure its not a 4L60E. A 4L60E is an electronicly controlled 700R-4.

    My Chevy isn't broken, its just out of gas.
     
  13. 75K5

    75K5 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    what do you guys know about the np241 and borg warner 4401. Are those AWD/full time 4wd?

    Thanks!
    Brian
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: what\'s best trans/xfer case for a 75?

    When they designed the Typhoon they robbed the AWD case off the Astro assembly line and went with it. A lot of Typoon's are modified heavily and run ~10 second quarter miles times with that same AWD case.[​IMG] I think for a sport type truck you'll want to shed as much weight as possible...and the 203 is quite honestly a very heavy t-case with an unnecessary low range.
    I think the best would be to graft the front frame section onto the 75...or find a way to graft the 75 body onto a newer frame.
    For some simplicity I'd stay with the 4L60E that already comes hooked to the Astro AWD case...

    Have you thought of using Corvette IRS? I seem to recall reading about a Vette IRS swap into a 90 1/2 ton lowrider (full-size) and it seemd to do well.

    Rene

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  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: what\'s best trans/xfer case for a 75?

    241 is part time...242, 262 are AWD capable.

    Rene

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  16. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Re: what\'s best trans/xfer case for a 75?

    Another thing to think about, especially with the 203 t-case.......which side is the driveshaft on in the front end? The GM versions are on the passenger side, but aren't the Tahoe's on the drivers side? [​IMG]


    I'm not picking my nose...I'm just pointing at my brain!! [​IMG]

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  17. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: what\'s best trans/xfer case for a 75?

    IFS is drivers side pumpkin...Astro case is driver sdie output...214, 242, 262 are all more common with driver sdie output than passenger side.

    Ford 203 would be driver side output if you had your heart set on one...

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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  18. four_by_ken

    four_by_ken 1/2 ton status

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    Re: what\'s best trans/xfer case for a 75?

    Just my opinion here... but...
    Sounds like a lot of money and a lot of time and a lot of fabricating for something that will weigh too much to truly handle and perform up to par with what is in the road now.
    Just doenst seem like a good idea to me.
    I am all for fabrication and interesting stuff, but just seems like the wrong direction to me.

    Ken H.



    '86 K5 up and coming
    14 bolt(Detroited),10 bolt,39.5 Boggers rear,
    TSLs front, 468 BBC, 350 trans, 205 transfer
    Rust free in Michigan!
     

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