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400SB/700R4 compatibility

Discussion in 'The Garage' started by blazin topless 75, Mar 17, 2004.

  1. blazin topless 75

    blazin topless 75 Registered Member

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    I need your help folks-will a stock 400SB be to much for a 700R4? I'm not going to be doing too much heavy wheeling-just some trails and mostly DD'ing. I will also be trailering my 3400LB boat.
     
  2. RustBuket

    RustBuket 1/2 ton status

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    If you're towing, Id say it'll probably blow up.
     
  3. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Stock its not a good idea. However if gone through it would be fine. Run a cooler of course. Also do not use the OD with any amount of weight in tow, for that matter you don't need OD in town either. /forums/images/graemlins/thumb.gif
     
  4. shane74

    shane74 1/2 ton status

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    I don't see why it's be an issue. GM put them in their /forums/images/graemlins/burb.gif as a standard powertrain combo ( my bro-in-law has that combo in his '87 /forums/images/graemlins/burb.gif). I had that exact same combo in a '79 /forums/images/graemlins/k5.gif and I had NO issues. I also had a 19' Reinel that I towed almost every weekend and even on some extened trips. It was on a single axle trailer too. My 79' never even broke a sweat. But, I didn't/don't tow in OD EVER. That makes the tranny slip too much when your pulling a heavy load and can burn it up pretty quick. Maybe the newer rigs are different, but for me towing in OD has always been bad juju.
     
  5. blazin topless 75

    blazin topless 75 Registered Member

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    Thanks everybody. I found an '87 donor truck for $500 that has a built 305 and a 700R4 that I was going to drop into my rig until I get my TH350/NP203 rebuilt.
     
  6. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    pull out the stock cooler and get a bigger one... also get a gauge. I think it will be fine what kind of gears are you running?
     
  7. blazin topless 75

    blazin topless 75 Registered Member

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  8. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I am running a built 406 that is making around 325HP and 425 ft lbs with a built th700R4 behind it. I like the combo a lot! I am running 4.10 gears with 35's and it seems to be ok for right now and I pull trailers all the time behind it without any issues what so ever. If your donor th700 is in good shape and you take care of the cooling issue than I would not worry about it much, even pulling your boat. BTW 3,500 lbs isn't all that much really.
     
  9. blazin topless 75

    blazin topless 75 Registered Member

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    What did you do to build it?
     
  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Almost everything. A LOT of parts have to be replaced to make it a very strong tranny. If your 400 is stock and there isn't any plans for more power than I would say a fresh 87'-later 700 with a good cooler and shift kit should hold up just fine.
     
  11. hi pinion

    hi pinion 3/4 ton status

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    yep,on that note i will see you on friday lol,hopefully running like a charm,jake /forums/images/graemlins/thumb.gif
     
  12. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Just in case you don't already know this I will tell you. If you want to install a 700R4 into your 75 K5 you will need to use a spacer between the tranny and T-case adapter since the TH350 and 700R4 output shafts are different lengths. You will also need to have the drivelines corrected since the 700R4 tranny is 1 7/8" longer than TH350 and also because you are needing the spacer. You will also need to address the TV cable and the TC lock-up. You will need to relocate the tranny crossmember as well.
     
  13. blazin topless 75

    blazin topless 75 Registered Member

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    Is that even with using the NP 208 and the shafts out of the donor truck?
     
  14. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Even if you use the whole drivetrain out of the donor truck some of the issues 4x4high mentioned need addrerssed. The TV cable needs the bracketry from a later truck to hook up to carb/injection. Your older truck does not contain wiring for lockup torque converter, you may have to wire in a switch or use a combination of two wiring harnesses. I also believe, based on my 12 bolt swap , that the 10 bolt u-joints on donor shafts are slightly bigger than the u-joints a 75 has (d44/12b). Hope it helps /forums/images/graemlins/thumb.gif
     
  15. blazin topless 75

    blazin topless 75 Registered Member

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    It does help-thanks. I was considering swapping out the entire wiring harness and fuse block because a lot of my wiring was "modified" making the accessories, interior lighting, backup lights, etc inoperable. I would probably just swap out any other wiring that I would need for the tranny at that time.
     
  16. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I also want to mention your sig says 9 inches of lift on 35's. You should remove some lift since you only have 35's. This will make it easier to shim you axle for proper u-joint angles. Or you can run a CV shaft. Just a thought /forums/images/graemlins/thumb.gif
     
  17. blazin topless 75

    blazin topless 75 Registered Member

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    I have 6" of suspension lift-the rest is in the body. I am thinking of taking the body lift out because I am running 35s, and with the bushwacker cut-outs it looks kind of silly on those "little" tires. I don't want to get bigger tires because I am trailering my ski boat and I don't want to scrape the prop with the additional height.
     
  18. blazin topless 75

    blazin topless 75 Registered Member

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    Paul I just looked at your pics-I've never seen the drive angle with the shackle flips-awesome! I think I'll have to invest in those as well... /forums/images/graemlins/peace.gif
     
  19. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    That angle made mine vibrate with stock shaft, I am running a CV shaft now with NO shims in axle. Basically with stock shafts the axle and transfercase need to point flat in relation to each other. With a CV shaft the axle just needs to point at transfercase. So in my case it worked great for a CV /forums/images/graemlins/thumb.gif
     

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