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Newbie wants to know how stout IS a diesel 700R4

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 4DiggerDan, Feb 4, 2003.

  1. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Howdy gents. I'm the newbie thats been adding all the posts to the engine related stuff over here. Like a good hillbilly, I sandbagged over here for a week or two before I registered and made posts.

    Anyhow, I'm an engine machinist with a serious 4 digger habbit. I bought a K5 from a gal local that had a blown up 6.2 diesel in it. I hate 6.2 diesels... It just so happens that I was in the process of building a roller cam 383 stroker on a late roller TBI block when this truck just sorta landed in my lap. It should be in the neighborhood of 430 horse, 480 Ft/Lbs at the crank. It has a 700R4 in it now, with what I think is a NP208 (Its big, its part time and it ain't a NP205.) I was told that the diesel and 3/4 ton 700's have bigger shafts than the RWD and 1/2 ton 700's. How much abuse will this combo take before it pops? I wheel pretty hard, but I'm good on maintenance. The plan is to go with a 4" lift, and 3/4 ton axles (early Dana 44 with the big wheel bearings, and a 14 bolt) and whatever metric tire comes close to 34" on 16" wheels. What I pull for gears will depend on which tranny I run. With an overdrive tranny I'd be thinking 4.56's.

    Next question... Will a NP205 bolt up to the 700R4? I'm not worried about fabricating a crossmember for it. I can handle that.

    Next question... The other tranny I've got access too is a TH400 that came out of a 6.5 powered 1/2 ton 2WD. I've got a 4x4 tailshaft that will mate up to a NP205, but other than that. Is a diesel TH400 any different than any other TH400? I've heard of guys digging up TH400s with square cut gears, and my local tranny guy say's they're bombproof. What did they come stock in??

    I'm kind of wanting to stay with the NP205 case, In the Chevy 4X4's I've owned they've been the most trouble free cases I've had. I'm not a big fan on NP203's, even when converted to part time with the Doug Nash kit. There's just too damn many parts in them for what they do. I've heard that the 208 is an aluminum cased version on the 203?

    I've got another couple weeks at least before I start putting this thing together. So far I've learned a lot on this forum. I'll be here for a while... I've always wanted a K5, I'm stoked /forums/images/graemlins/thumb.gif
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    If you are nasty to a 700/208 combo it will be nasty to you. With that much torque I doubt that the 700 will last very long in stock trim. I am on my 4th 700 with a mild 350. I always toast 2nd gear in mine. If you plan on running with a heavy foot then I would put that 400/205 in. You can have a 700 built to take that amount of power, but they are not cheap. $1200+. I am going to try and make a 700/208 live behind 400/450 numbers one day, but it will be with a built 700 and a rebuilt 208. I don't drive like a madman so I think I might be able to make it last for awhile.
     
  3. outlaw612

    outlaw612 1/2 ton status

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    On the 700to 205, the answer is yes and no. Yes you can make them bolt up but no they wont without modification. You can either buy a spacer($60) to use between the 700r4 and adapter, or you can buy the correct out put shaft for the 700r4.($$$)

    The other stipulation, is you will need a 205 off of a th350. This will give you the 27 spline which is the same as the 700r4.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    One other consideration is the shift points. Talk to your tranny guy about changing the governor for you. A stock 700R4 (or even the 400 that you're considering) from a gas engine application will typically upshift around 4,500 RPM at wide open throttle. The same tranny from a diesel application will upshift at around 2,800 RPM at wide open throttle. /forums/images/graemlins/shocked.gif Not the hot ticket for a healthy small block. /forums/images/graemlins/wink.gif
     
  5. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Thanks guys... You kind of told me what I already knew. I'd like an overdrive tranny, but I'd probably break it while I was plowing snow with my hood in the ass end of nowhere Montana. Thanks for the heads up on changing the governor, I would have been pissed off after doing up a tranny and then having it shift just when my 383 is coming alive.

    Next question, what is the spline count on the input shaft on a NP205 that was origional to a TH400? But then I guess it doesn't matter if I have to tear apart the 2WD TH400 to put a 4X4 tailshaft into it anyhow. Is there one thats stouter than the rest??
     
  6. wrathORC

    wrathORC 1/2 ton status

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    Straight cut 400s can be found in busses, box vans, et cetera. The telltale sign of one is a nifty whine going down the road.
     
  7. HarryH3

    HarryH3 1 ton status Author

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    A 205 that was behind a Turbo 400 will have a 32 spline input shaft. /forums/images/graemlins/cool.gif They aren't nearly as plentiful as the 27 spline version. /forums/images/graemlins/frown.gif
     
  8. imiceman44

    imiceman44 1 ton status

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    You don't have to change the shaft on a th400 they are the same 2wd and 4wd.
    There was different lengths though some in cadilacs, longer, and some in older trucks shorter.
    The more common is the middle size which is the same as the 4x4.
     
  9. the professor

    the professor 1/2 ton status

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    Yes a "short tailshaft" 2wd TH400 will bolt up to a NP205, BUT you have to cut about 1/2 off the output shaft (the differenc between a 2wd and 4wd shaft), Its only hardened on the surface, so it is easy...should stick out about 4.5in
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    B&M has a "governor kit" to change your shiftpoints...be patient its a pain in the a**...
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    I did a wide ration 2.71 first in my TH400, took about 25 trys to get the shiftpoint right...but worth it...
     
  10. the professor

    the professor 1/2 ton status

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    acording to a few guys at 'Chevvy talk'
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    http://chevytalk.com/
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    a few guys with TH700's and 208 behind Diesels have over 150,000 miles on original transmissions..
    --
    having worked on many diesels, the "torque" output is overrated...its all low rpm, easy on the trans...NOTHING like a SB 400 or BB454
     
  11. the professor

    the professor 1/2 ton status

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    B&M rates their highly modified TH700r4, 4L60 @ 450 lb ft MAX...they DO NOT recommend them behind even a STOCK 454..so if you motor makes that kind of torque, go with a TH350 or 400...
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    I use a TH400 w/ a 2.71 first gear, wide ratio gearset, 2100rpm converter.and 27spline conversion.. .NP205..with an .and "tall", 3.52 diff gears and 32" tires behind a mildly modified 454.... /forums/images/graemlins/cool.gif
     
  12. pr1aw

    pr1aw 1/2 ton status

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    The TH400 with the straight cut gears is known as a TH475 for info purposes.
     
  13. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Thanks for the info guys... I learned a lot about TH400's so far. Do they make a 27 spline output shaft to go out of a TH400 and into a NP205? I was really hoping to find a 3/4 ton truck that had the TH400 and NP205 stock. Then the front driveline and crossmember would be pretty much a drop in. However, I just bought another truck today pretty much for a set of axles (Dana 44 front and 14 bolt FF rear with 4.10's /forums/images/graemlins/thumb.gif ) engine brackets, HEI, and a vacuum braking booster. So now I'm going to have to buy JUST a NP205 and live with what I got. Now I've got a set of 10 bolts, TH350, NP203, NP208, 700R4, a blow'd up 6.2 diesel, 350 CSB core long block, a PS front fender for a '76 PU (the only one not dented or rotted out,) and a partridge in a pear tree for horse-tradin' material.

    The TH400 I got came out of my bosses donor truck for his 4x4 truck we're currently building. He bought a 2WD '86 for the body to put on his '73 3/4 ton frame. His truck project is coming along quite nicely, and I'm jelous as HELL!!! Thats why I bought the Blazer, I gotta try and one up him. I can't have my beat up '76 Scotty stepside parked next to THAT, I'll feel my penis shrinking by the minute!!! /forums/images/graemlins/frown.gif

    I was talking to him today about recalibrating the govenor in that TH400. He told me how he did the one in his car (an 86 Regal thats completely pimped out, with a 5.7" rod 400 CSB that makes CBB torque.) He said all he did was mow about .010" at a time off the weights (with the B&M springs) and weigh them on a PACT digital reloading scale. Its shifts are calibrated PERFECT to the way the engine behaves. It cracks us up, anytime somebody sees his Regal, they say "Thats the sweetest Monte Carlo I've eve seen." We just giggle and say "Yeah, its one of the rarest G bodies GM ever made..." He's into G bodies so much that the stock car we're sponsoring this year is a Regal. There's about a bazillion reasons that Regals make better stock cars than Montes. But I've gone off topic long enough as it is /forums/images/graemlins/ooo.gif
     
  14. HarryH3

    HarryH3 1 ton status Author

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    Check with Stephen at www.offroaddesign.com I think he sells an input shaft for the 205 that will let you convert a 27-spline version into a 32-spline version. Then the 205 will bolt right on to your Turbo 400. /forums/images/graemlins/cool.gif It requires a slight bit of machining on the front of the transfer case, to install the larger bearing that is used on the 32-spline version. /forums/images/graemlins/cool.gif
     
  15. BlazinRojo

    BlazinRojo 1/2 ton status

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    Check out the level 3 700r4 from Bowtie Overdrives (www.700r4.com) Says its good to 600 hp. I have their level 2 tranny (good to 450) and LOVE IT. Shifts at around 4900 with the pedal floored (probably not good for my NP208 though) Just another option if you with to keep the 700r4.
     
  16. 4DiggerDan

    4DiggerDan 1/2 ton status

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    Thanks again all.. Now all I need is a NP205 and I'm ready to start building a K5 out of a 3d jigsaw puzzle thats all over my bosses garage. We're going to try to get his truck project finished. I was over there until about 9:30 figuring out what a pain in the ass it is installing a '86 body (off a 2WD) onto a '73 3/4 ton frame. I'm thinking where that went wrong was buying a set of poly body bushings. When I left, I had all the corners pretty close (like whthin 1/16 of an inch) but something still doesn't look right. I think I need to grind off about 1/4" off the back two cab mounts. I'd have asked him what he thought if he wasn't out on a DATE!!!!

    I need a woman. I can't stop thinking about 4X4's.

    Are K5's chick magnets?? Could you make it any worse if you painted "I'm topless, why aren't you?" on the tailgate?? /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
     

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